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| author | John Ericson <John.Ericson@Obsidian.Systems> | 2021-01-10 02:01:43 +0000 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2021-01-23 21:32:47 -0500 |
| commit | 81f0665513d65c2d7e544cbe8adeff4b0d6fdfff (patch) | |
| tree | 9e55698fc5cc041e8623eff2978eb94b72894130 /compiler/Language | |
| parent | e6e1cf743c6de87c376c32d2279e2d684151f3d7 (diff) | |
| download | haskell-81f0665513d65c2d7e544cbe8adeff4b0d6fdfff.tar.gz | |
Separate AST from GhcPass (#18936)
----------------
What:
There are two splits.
The first spit is:
- `Language.Haskell.Syntax.Extension`
- `GHC.Hs.Extension`
where the former now just contains helpers like `NoExtCon` and all the
families, and the latter is everything having to do with `GhcPass`.
The second split is:
- `Language.Haskell.Syntax.<mod>`
- `GHC.Hs.<mod>`
Where the former contains all the data definitions, and the few helpers
that don't use `GhcPass`, and the latter contains everything else. The
second modules also reexport the former.
----------------
Why:
See the issue for more details, but in short answer is we're trying to
grasp at the modularity TTG is supposed to offer, after a long time of
mainly just getting the safety benefits of more complete pattern
matching on the AST.
Now, we have an AST datatype which, without `GhcPass` is decently
stripped of GHC-specific concerns. Whereas before, not was it
GHC-specific, it was aware of all the GHC phases despite the
parameterization, with the instances and parametric data structure
side-by-side.
For what it's worth there are also some smaller, imminent benefits:
- The latter change also splits a strongly connected component in two,
since none of the `Language.Haskell.Syntax.*` modules import the older
ones.
- A few TTG violations (Using GhcPass directly in the AST) in `Expr` are
now more explicitly accounted for with new type families to provide the
necessary indirection.
-----------------
Future work:
- I don't see why all the type families should live in
`Language.Haskell.Syntax.Extension`. That seems anti-modular for
little benefit. All the ones used just once can be moved next to the
AST type they serve as an extension point for.
- Decide what to do with the `Outputable` instances. Some of these are
no orphans because they referred to `GhcPass`, and had to be moved. I
think the types could be generalized so they don't refer to `GhcPass`
and therefore can be moved back, but having gotten flak for increasing
the size and complexity types when generalizing before, I did *not*
want to do this.
- We should triage the remaining contents of `GHC.Hs.<mod>`. The
renaming helpers are somewhat odd for needing `GhcPass`. We might
consider if they are a) in fact only needed by one phase b) can be
generalized to be non-GhcPass-specific (e.g. take a callback rather
than GADT-match with `IsPass`) and then they can live in
`Language.Haskell.Syntax.<mod>`.
For more details, see
https://gitlab.haskell.org/ghc/ghc/-/wikis/implementing-trees-that-grow
Bumps Haddock submodule
Diffstat (limited to 'compiler/Language')
| -rw-r--r-- | compiler/Language/Haskell/Syntax.hs | 58 | ||||
| -rw-r--r-- | compiler/Language/Haskell/Syntax/Binds.hs | 944 | ||||
| -rw-r--r-- | compiler/Language/Haskell/Syntax/Decls.hs | 1804 | ||||
| -rw-r--r-- | compiler/Language/Haskell/Syntax/Expr.hs | 1776 | ||||
| -rw-r--r-- | compiler/Language/Haskell/Syntax/Expr.hs-boot | 22 | ||||
| -rw-r--r-- | compiler/Language/Haskell/Syntax/Extension.hs | 665 | ||||
| -rw-r--r-- | compiler/Language/Haskell/Syntax/Lit.hs | 204 | ||||
| -rw-r--r-- | compiler/Language/Haskell/Syntax/Pat.hs | 374 | ||||
| -rw-r--r-- | compiler/Language/Haskell/Syntax/Pat.hs-boot | 13 | ||||
| -rw-r--r-- | compiler/Language/Haskell/Syntax/Type.hs | 1304 |
10 files changed, 7164 insertions, 0 deletions
diff --git a/compiler/Language/Haskell/Syntax.hs b/compiler/Language/Haskell/Syntax.hs new file mode 100644 index 0000000000..9da54cd8ed --- /dev/null +++ b/compiler/Language/Haskell/Syntax.hs @@ -0,0 +1,58 @@ +{- +(c) The University of Glasgow 2006 +(c) The GRASP/AQUA Project, Glasgow University, 1992-1998 + +\section{Haskell abstract syntax definition} + +This module glues together the pieces of the Haskell abstract syntax, +which is declared in the various \tr{Hs*} modules. This module, +therefore, is almost nothing but re-exporting. +-} + +{-# LANGUAGE DeriveDataTypeable #-} +{-# LANGUAGE StandaloneDeriving #-} +{-# LANGUAGE FlexibleContexts #-} +{-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow] + -- in module Language.Haskell.Syntax.Extension +{-# LANGUAGE ConstraintKinds #-} +{-# LANGUAGE TypeFamilies #-} +{-# LANGUAGE FlexibleInstances #-} -- For deriving instance Data + +-- See Note [Language.Haskell.Syntax.* Hierarchy] for why not GHC.Hs.* +module Language.Haskell.Syntax ( + module Language.Haskell.Syntax.Binds, + module Language.Haskell.Syntax.Decls, + module Language.Haskell.Syntax.Expr, + module Language.Haskell.Syntax.Lit, + module Language.Haskell.Syntax.Pat, + module Language.Haskell.Syntax.Type, + module Language.Haskell.Syntax.Extension, +) where + +import Language.Haskell.Syntax.Decls +import Language.Haskell.Syntax.Binds +import Language.Haskell.Syntax.Expr +import Language.Haskell.Syntax.Lit +import Language.Haskell.Syntax.Extension +import Language.Haskell.Syntax.Pat +import Language.Haskell.Syntax.Type + +{- +Note [Language.Haskell.Syntax.* Hierarchy] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Why are these modules not 'GHC.Hs.*', or some other 'GHC.*'? The answer +is that they are to be separated from GHC and put into another package, +in accordance with the final goals of Trees that Grow. (See Note [Trees +that grow] in 'Language.Haskell.Syntax.Extension'.) + +We cannot separate them yet, but by giving them names like so, we hope +to remind others that the goal is to factor them out, and therefore +dependencies on the rest of GHC should never be added, only removed. + +For more details, see +https://gitlab.haskell.org/ghc/ghc/-/wikis/implementing-trees-that-grow +-} + + +-- TODO Add TTG parameter to 'HsModule' and move here. diff --git a/compiler/Language/Haskell/Syntax/Binds.hs b/compiler/Language/Haskell/Syntax/Binds.hs new file mode 100644 index 0000000000..6f7283be86 --- /dev/null +++ b/compiler/Language/Haskell/Syntax/Binds.hs @@ -0,0 +1,944 @@ +{-# LANGUAGE ConstraintKinds #-} +{-# LANGUAGE DeriveDataTypeable #-} +{-# LANGUAGE DeriveFunctor #-} +{-# LANGUAGE FlexibleContexts #-} +{-# LANGUAGE FlexibleInstances #-} +{-# LANGUAGE LambdaCase #-} +{-# LANGUAGE ScopedTypeVariables #-} +{-# LANGUAGE TypeApplications #-} +{-# LANGUAGE TypeFamilies #-} +{-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow] + -- in module Language.Haskell.Syntax.Extension +{-# LANGUAGE ViewPatterns #-} + + +{- +(c) The University of Glasgow 2006 +(c) The GRASP/AQUA Project, Glasgow University, 1992-1998 + +\section[HsBinds]{Abstract syntax: top-level bindings and signatures} + +Datatype for: @BindGroup@, @Bind@, @Sig@, @Bind@. +-} + +-- See Note [Language.Haskell.Syntax.* Hierarchy] for why not GHC.Hs.* +module Language.Haskell.Syntax.Binds where + +import GHC.Prelude + +import {-# SOURCE #-} Language.Haskell.Syntax.Expr + ( LHsExpr + , MatchGroup + , GRHSs ) +import {-# SOURCE #-} Language.Haskell.Syntax.Pat + ( LPat ) + +import Language.Haskell.Syntax.Extension +import Language.Haskell.Syntax.Type +import GHC.Core +import GHC.Tc.Types.Evidence +import GHC.Core.Type +import GHC.Types.Basic +import GHC.Types.SourceText +import GHC.Types.SrcLoc as SrcLoc +import GHC.Types.Var +import GHC.Types.Fixity +import GHC.Data.Bag +import GHC.Data.BooleanFormula (LBooleanFormula) + +import GHC.Utils.Outputable + +import Data.Data hiding ( Fixity ) +import Data.Void + +{- +************************************************************************ +* * +\subsection{Bindings: @BindGroup@} +* * +************************************************************************ + +Global bindings (where clauses) +-} + +-- During renaming, we need bindings where the left-hand sides +-- have been renamed but the right-hand sides have not. +-- Other than during renaming, these will be the same. + +-- | Haskell Local Bindings +type HsLocalBinds id = HsLocalBindsLR id id + +-- | Located Haskell local bindings +type LHsLocalBinds id = XRec id (HsLocalBinds id) + +-- | Haskell Local Bindings with separate Left and Right identifier types +-- +-- Bindings in a 'let' expression +-- or a 'where' clause +data HsLocalBindsLR idL idR + = HsValBinds + (XHsValBinds idL idR) + (HsValBindsLR idL idR) + -- ^ Haskell Value Bindings + + -- There should be no pattern synonyms in the HsValBindsLR + -- These are *local* (not top level) bindings + -- The parser accepts them, however, leaving the + -- renamer to report them + + | HsIPBinds + (XHsIPBinds idL idR) + (HsIPBinds idR) + -- ^ Haskell Implicit Parameter Bindings + + | EmptyLocalBinds (XEmptyLocalBinds idL idR) + -- ^ Empty Local Bindings + + | XHsLocalBindsLR + !(XXHsLocalBindsLR idL idR) + +type LHsLocalBindsLR idL idR = XRec idL (HsLocalBindsLR idL idR) + + +-- | Haskell Value Bindings +type HsValBinds id = HsValBindsLR id id + +-- | Haskell Value bindings with separate Left and Right identifier types +-- (not implicit parameters) +-- Used for both top level and nested bindings +-- May contain pattern synonym bindings +data HsValBindsLR idL idR + = -- | Value Bindings In + -- + -- Before renaming RHS; idR is always RdrName + -- Not dependency analysed + -- Recursive by default + ValBinds + (XValBinds idL idR) + (LHsBindsLR idL idR) [LSig idR] + + -- | Value Bindings Out + -- + -- After renaming RHS; idR can be Name or Id Dependency analysed, + -- later bindings in the list may depend on earlier ones. + | XValBindsLR + !(XXValBindsLR idL idR) + +-- --------------------------------------------------------------------- + +-- | Located Haskell Binding +type LHsBind id = LHsBindLR id id + +-- | Located Haskell Bindings +type LHsBinds id = LHsBindsLR id id + +-- | Haskell Binding +type HsBind id = HsBindLR id id + +-- | Located Haskell Bindings with separate Left and Right identifier types +type LHsBindsLR idL idR = Bag (LHsBindLR idL idR) + +-- | Located Haskell Binding with separate Left and Right identifier types +type LHsBindLR idL idR = XRec idL (HsBindLR idL idR) + +{- Note [FunBind vs PatBind] + ~~~~~~~~~~~~~~~~~~~~~~~~~ +The distinction between FunBind and PatBind is a bit subtle. FunBind covers +patterns which resemble function bindings and simple variable bindings. + + f x = e + f !x = e + f = e + !x = e -- FunRhs has SrcStrict + x `f` y = e -- FunRhs has Infix + +The actual patterns and RHSs of a FunBind are encoding in fun_matches. +The m_ctxt field of each Match in fun_matches will be FunRhs and carries +two bits of information about the match, + + * The mc_fixity field on each Match describes the fixity of the + function binder in that match. E.g. this is legal: + f True False = e1 + True `f` True = e2 + + * The mc_strictness field is used /only/ for nullary FunBinds: ones + with one Match, which has no pats. For these, it describes whether + the match is decorated with a bang (e.g. `!x = e`). + +By contrast, PatBind represents data constructor patterns, as well as a few +other interesting cases. Namely, + + Just x = e + (x) = e + x :: Ty = e +-} + +-- | Haskell Binding with separate Left and Right id's +data HsBindLR idL idR + = -- | Function-like Binding + -- + -- FunBind is used for both functions @f x = e@ + -- and variables @f = \x -> e@ + -- and strict variables @!x = x + 1@ + -- + -- Reason 1: Special case for type inference: see 'GHC.Tc.Gen.Bind.tcMonoBinds'. + -- + -- Reason 2: Instance decls can only have FunBinds, which is convenient. + -- If you change this, you'll need to change e.g. rnMethodBinds + -- + -- But note that the form @f :: a->a = ...@ + -- parses as a pattern binding, just like + -- @(f :: a -> a) = ... @ + -- + -- Strict bindings have their strictness recorded in the 'SrcStrictness' of their + -- 'MatchContext'. See Note [FunBind vs PatBind] for + -- details about the relationship between FunBind and PatBind. + -- + -- 'GHC.Parser.Annotation.AnnKeywordId's + -- + -- - 'GHC.Parser.Annotation.AnnFunId', attached to each element of fun_matches + -- + -- - 'GHC.Parser.Annotation.AnnEqual','GHC.Parser.Annotation.AnnWhere', + -- 'GHC.Parser.Annotation.AnnOpen','GHC.Parser.Annotation.AnnClose', + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + FunBind { + + fun_ext :: XFunBind idL idR, + + -- ^ After the renamer (but before the type-checker), this contains the + -- locally-bound free variables of this defn. See Note [Bind free vars] + -- + -- After the type-checker, this contains a coercion from the type of + -- the MatchGroup to the type of the Id. Example: + -- + -- @ + -- f :: Int -> forall a. a -> a + -- f x y = y + -- @ + -- + -- Then the MatchGroup will have type (Int -> a' -> a') + -- (with a free type variable a'). The coercion will take + -- a CoreExpr of this type and convert it to a CoreExpr of + -- type Int -> forall a'. a' -> a' + -- Notice that the coercion captures the free a'. + + fun_id :: LIdP idL, -- Note [fun_id in Match] in GHC.Hs.Expr + + fun_matches :: MatchGroup idR (LHsExpr idR), -- ^ The payload + + fun_tick :: [Tickish Id] -- ^ Ticks to put on the rhs, if any + } + + -- | Pattern Binding + -- + -- The pattern is never a simple variable; + -- That case is done by FunBind. + -- See Note [FunBind vs PatBind] for details about the + -- relationship between FunBind and PatBind. + + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnBang', + -- 'GHC.Parser.Annotation.AnnEqual','GHC.Parser.Annotation.AnnWhere', + -- 'GHC.Parser.Annotation.AnnOpen','GHC.Parser.Annotation.AnnClose', + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | PatBind { + pat_ext :: XPatBind idL idR, -- ^ See Note [Bind free vars] + pat_lhs :: LPat idL, + pat_rhs :: GRHSs idR (LHsExpr idR), + pat_ticks :: ([Tickish Id], [[Tickish Id]]) + -- ^ Ticks to put on the rhs, if any, and ticks to put on + -- the bound variables. + } + + -- | Variable Binding + -- + -- Dictionary binding and suchlike. + -- All VarBinds are introduced by the type checker + | VarBind { + var_ext :: XVarBind idL idR, + var_id :: IdP idL, + var_rhs :: LHsExpr idR -- ^ Located only for consistency + } + + -- | Abstraction Bindings + | AbsBinds { -- Binds abstraction; TRANSLATION + abs_ext :: XAbsBinds idL idR, + abs_tvs :: [TyVar], + abs_ev_vars :: [EvVar], -- ^ Includes equality constraints + + -- | AbsBinds only gets used when idL = idR after renaming, + -- but these need to be idL's for the collect... code in HsUtil + -- to have the right type + abs_exports :: [ABExport idL], + + -- | Evidence bindings + -- Why a list? See "GHC.Tc.TyCl.Instance" + -- Note [Typechecking plan for instance declarations] + abs_ev_binds :: [TcEvBinds], + + -- | Typechecked user bindings + abs_binds :: LHsBinds idL, + + abs_sig :: Bool -- See Note [The abs_sig field of AbsBinds] + } + + -- | Patterns Synonym Binding + | PatSynBind + (XPatSynBind idL idR) + (PatSynBind idL idR) + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnPattern', + -- 'GHC.Parser.Annotation.AnnLarrow','GHC.Parser.Annotation.AnnEqual', + -- 'GHC.Parser.Annotation.AnnWhere' + -- 'GHC.Parser.Annotation.AnnOpen' @'{'@,'GHC.Parser.Annotation.AnnClose' @'}'@ + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | XHsBindsLR !(XXHsBindsLR idL idR) + + + -- Consider (AbsBinds tvs ds [(ftvs, poly_f, mono_f) binds] + -- + -- Creates bindings for (polymorphic, overloaded) poly_f + -- in terms of monomorphic, non-overloaded mono_f + -- + -- Invariants: + -- 1. 'binds' binds mono_f + -- 2. ftvs is a subset of tvs + -- 3. ftvs includes all tyvars free in ds + -- + -- See Note [AbsBinds] + +-- | Abstraction Bindings Export +data ABExport p + = ABE { abe_ext :: XABE p + , abe_poly :: IdP p -- ^ Any INLINE pragma is attached to this Id + , abe_mono :: IdP p + , abe_wrap :: HsWrapper -- ^ See Note [ABExport wrapper] + -- Shape: (forall abs_tvs. abs_ev_vars => abe_mono) ~ abe_poly + , abe_prags :: TcSpecPrags -- ^ SPECIALISE pragmas + } + | XABExport !(XXABExport p) + + +-- | - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnPattern', +-- 'GHC.Parser.Annotation.AnnEqual','GHC.Parser.Annotation.AnnLarrow', +-- 'GHC.Parser.Annotation.AnnWhere','GHC.Parser.Annotation.AnnOpen' @'{'@, +-- 'GHC.Parser.Annotation.AnnClose' @'}'@, + +-- For details on above see note [Api annotations] in GHC.Parser.Annotation + +-- | Pattern Synonym binding +data PatSynBind idL idR + = PSB { psb_ext :: XPSB idL idR, -- ^ Post renaming, FVs. + -- See Note [Bind free vars] + psb_id :: LIdP idL, -- ^ Name of the pattern synonym + psb_args :: HsPatSynDetails idR, -- ^ Formal parameter names + psb_def :: LPat idR, -- ^ Right-hand side + psb_dir :: HsPatSynDir idR -- ^ Directionality + } + | XPatSynBind !(XXPatSynBind idL idR) + +{- +Note [AbsBinds] +~~~~~~~~~~~~~~~ +The AbsBinds constructor is used in the output of the type checker, to +record *typechecked* and *generalised* bindings. Specifically + + AbsBinds { abs_tvs = tvs + , abs_ev_vars = [d1,d2] + , abs_exports = [ABE { abe_poly = fp, abe_mono = fm + , abe_wrap = fwrap } + ABE { slly for g } ] + , abs_ev_binds = DBINDS + , abs_binds = BIND[fm,gm] } + +where 'BIND' binds the monomorphic Ids 'fm' and 'gm', means + + fp = fwrap [/\ tvs. \d1 d2. letrec { DBINDS ] + [ ; BIND[fm,gm] } ] + [ in fm ] + + gp = ...same again, with gm instead of fm + +The 'fwrap' is an impedance-matcher that typically does nothing; see +Note [ABExport wrapper]. + +This is a pretty bad translation, because it duplicates all the bindings. +So the desugarer tries to do a better job: + + fp = /\ [a,b] -> \ [d1,d2] -> case tp [a,b] [d1,d2] of + (fm,gm) -> fm + ..ditto for gp.. + + tp = /\ [a,b] -> \ [d1,d2] -> letrec { DBINDS; BIND } + in (fm,gm) + +In general: + + * abs_tvs are the type variables over which the binding group is + generalised + * abs_ev_var are the evidence variables (usually dictionaries) + over which the binding group is generalised + * abs_binds are the monomorphic bindings + * abs_ex_binds are the evidence bindings that wrap the abs_binds + * abs_exports connects the monomorphic Ids bound by abs_binds + with the polymorphic Ids bound by the AbsBinds itself. + +For example, consider a module M, with this top-level binding, where +there is no type signature for M.reverse, + M.reverse [] = [] + M.reverse (x:xs) = M.reverse xs ++ [x] + +In Hindley-Milner, a recursive binding is typechecked with the +*recursive* uses being *monomorphic*. So after typechecking *and* +desugaring we will get something like this + + M.reverse :: forall a. [a] -> [a] + = /\a. letrec + reverse :: [a] -> [a] = \xs -> case xs of + [] -> [] + (x:xs) -> reverse xs ++ [x] + in reverse + +Notice that 'M.reverse' is polymorphic as expected, but there is a local +definition for plain 'reverse' which is *monomorphic*. The type variable +'a' scopes over the entire letrec. + +That's after desugaring. What about after type checking but before +desugaring? That's where AbsBinds comes in. It looks like this: + + AbsBinds { abs_tvs = [a] + , abs_ev_vars = [] + , abs_exports = [ABE { abe_poly = M.reverse :: forall a. [a] -> [a], + , abe_mono = reverse :: [a] -> [a]}] + , abs_ev_binds = {} + , abs_binds = { reverse :: [a] -> [a] + = \xs -> case xs of + [] -> [] + (x:xs) -> reverse xs ++ [x] } } + +Here, + + * abs_tvs says what type variables are abstracted over the binding + group, just 'a' in this case. + * abs_binds is the *monomorphic* bindings of the group + * abs_exports describes how to get the polymorphic Id 'M.reverse' + from the monomorphic one 'reverse' + +Notice that the *original* function (the polymorphic one you thought +you were defining) appears in the abe_poly field of the +abs_exports. The bindings in abs_binds are for fresh, local, Ids with +a *monomorphic* Id. + +If there is a group of mutually recursive (see Note [Polymorphic +recursion]) functions without type signatures, we get one AbsBinds +with the monomorphic versions of the bindings in abs_binds, and one +element of abe_exports for each variable bound in the mutually +recursive group. This is true even for pattern bindings. Example: + (f,g) = (\x -> x, f) +After type checking we get + AbsBinds { abs_tvs = [a] + , abs_exports = [ ABE { abe_poly = M.f :: forall a. a -> a + , abe_mono = f :: a -> a } + , ABE { abe_poly = M.g :: forall a. a -> a + , abe_mono = g :: a -> a }] + , abs_binds = { (f,g) = (\x -> x, f) } + +Note [Polymorphic recursion] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Consider + Rec { f x = ...(g ef)... + + ; g :: forall a. [a] -> [a] + ; g y = ...(f eg)... } + +These bindings /are/ mutually recursive (f calls g, and g calls f). +But we can use the type signature for g to break the recursion, +like this: + + 1. Add g :: forall a. [a] -> [a] to the type environment + + 2. Typecheck the definition of f, all by itself, + including generalising it to find its most general + type, say f :: forall b. b -> b -> [b] + + 3. Extend the type environment with that type for f + + 4. Typecheck the definition of g, all by itself, + checking that it has the type claimed by its signature + +Steps 2 and 4 each generate a separate AbsBinds, so we end +up with + Rec { AbsBinds { ...for f ... } + ; AbsBinds { ...for g ... } } + +This approach allows both f and to call each other +polymorphically, even though only g has a signature. + +We get an AbsBinds that encompasses multiple source-program +bindings only when + * Each binding in the group has at least one binder that + lacks a user type signature + * The group forms a strongly connected component + + +Note [The abs_sig field of AbsBinds] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +The abs_sig field supports a couple of special cases for bindings. +Consider + + x :: Num a => (# a, a #) + x = (# 3, 4 #) + +The general desugaring for AbsBinds would give + + x = /\a. \ ($dNum :: Num a) -> + letrec xm = (# fromInteger $dNum 3, fromInteger $dNum 4 #) in + xm + +But that has an illegal let-binding for an unboxed tuple. In this +case we'd prefer to generate the (more direct) + + x = /\ a. \ ($dNum :: Num a) -> + (# fromInteger $dNum 3, fromInteger $dNum 4 #) + +A similar thing happens with representation-polymorphic defns +(#11405): + + undef :: forall (r :: RuntimeRep) (a :: TYPE r). HasCallStack => a + undef = error "undef" + +Again, the vanilla desugaring gives a local let-binding for a +representation-polymorphic (undefm :: a), which is illegal. But +again we can desugar without a let: + + undef = /\ a. \ (d:HasCallStack) -> error a d "undef" + +The abs_sig field supports this direct desugaring, with no local +let-binding. When abs_sig = True + + * the abs_binds is single FunBind + + * the abs_exports is a singleton + + * we have a complete type sig for binder + and hence the abs_binds is non-recursive + (it binds the mono_id but refers to the poly_id + +These properties are exploited in GHC.HsToCore.Binds.dsAbsBinds to +generate code without a let-binding. + +Note [ABExport wrapper] +~~~~~~~~~~~~~~~~~~~~~~~ +Consider + (f,g) = (\x.x, \y.y) +This ultimately desugars to something like this: + tup :: forall a b. (a->a, b->b) + tup = /\a b. (\x:a.x, \y:b.y) + f :: forall a. a -> a + f = /\a. case tup a Any of + (fm::a->a,gm:Any->Any) -> fm + ...similarly for g... + +The abe_wrap field deals with impedance-matching between + (/\a b. case tup a b of { (f,g) -> f }) +and the thing we really want, which may have fewer type +variables. The action happens in GHC.Tc.Gen.Bind.mkExport. + +Note [Bind free vars] +~~~~~~~~~~~~~~~~~~~~~ +The bind_fvs field of FunBind and PatBind records the free variables +of the definition. It is used for the following purposes + +a) Dependency analysis prior to type checking + (see GHC.Tc.Gen.Bind.tc_group) + +b) Deciding whether we can do generalisation of the binding + (see GHC.Tc.Gen.Bind.decideGeneralisationPlan) + +c) Deciding whether the binding can be used in static forms + (see GHC.Tc.Gen.Expr.checkClosedInStaticForm for the HsStatic case and + GHC.Tc.Gen.Bind.isClosedBndrGroup). + +Specifically, + + * bind_fvs includes all free vars that are defined in this module + (including top-level things and lexically scoped type variables) + + * bind_fvs excludes imported vars; this is just to keep the set smaller + + * Before renaming, and after typechecking, the field is unused; + it's just an error thunk +-} + + +{- +************************************************************************ +* * + Implicit parameter bindings +* * +************************************************************************ +-} + +-- | Haskell Implicit Parameter Bindings +data HsIPBinds id + = IPBinds + (XIPBinds id) + [LIPBind id] + -- TcEvBinds -- Only in typechecker output; binds + -- -- uses of the implicit parameters + | XHsIPBinds !(XXHsIPBinds id) + + +-- | Located Implicit Parameter Binding +type LIPBind id = XRec id (IPBind id) +-- ^ May have 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnSemi' when in a +-- list + +-- For details on above see note [Api annotations] in GHC.Parser.Annotation + +-- | Implicit parameter bindings. +-- +-- These bindings start off as (Left "x") in the parser and stay +-- that way until after type-checking when they are replaced with +-- (Right d), where "d" is the name of the dictionary holding the +-- evidence for the implicit parameter. +-- +-- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnEqual' + +-- For details on above see note [Api annotations] in GHC.Parser.Annotation +data IPBind id + = IPBind + (XCIPBind id) + (Either (XRec id HsIPName) (IdP id)) + (LHsExpr id) + | XIPBind !(XXIPBind id) + +{- +************************************************************************ +* * +\subsection{@Sig@: type signatures and value-modifying user pragmas} +* * +************************************************************************ + +It is convenient to lump ``value-modifying'' user-pragmas (e.g., +``specialise this function to these four types...'') in with type +signatures. Then all the machinery to move them into place, etc., +serves for both. +-} + +-- | Located Signature +type LSig pass = XRec pass (Sig pass) + +-- | Signatures and pragmas +data Sig pass + = -- | An ordinary type signature + -- + -- > f :: Num a => a -> a + -- + -- After renaming, this list of Names contains the named + -- wildcards brought into scope by this signature. For a signature + -- @_ -> _a -> Bool@, the renamer will leave the unnamed wildcard @_@ + -- untouched, and the named wildcard @_a@ is then replaced with + -- fresh meta vars in the type. Their names are stored in the type + -- signature that brought them into scope, in this third field to be + -- more specific. + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnDcolon', + -- 'GHC.Parser.Annotation.AnnComma' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + TypeSig + (XTypeSig pass) + [LIdP pass] -- LHS of the signature; e.g. f,g,h :: blah + (LHsSigWcType pass) -- RHS of the signature; can have wildcards + + -- | A pattern synonym type signature + -- + -- > pattern Single :: () => (Show a) => a -> [a] + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnPattern', + -- 'GHC.Parser.Annotation.AnnDcolon','GHC.Parser.Annotation.AnnForall' + -- 'GHC.Parser.Annotation.AnnDot','GHC.Parser.Annotation.AnnDarrow' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | PatSynSig (XPatSynSig pass) [LIdP pass] (LHsSigType pass) + -- P :: forall a b. Req => Prov => ty + + -- | A signature for a class method + -- False: ordinary class-method signature + -- True: generic-default class method signature + -- e.g. class C a where + -- op :: a -> a -- Ordinary + -- default op :: Eq a => a -> a -- Generic default + -- No wildcards allowed here + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnDefault', + -- 'GHC.Parser.Annotation.AnnDcolon' + | ClassOpSig (XClassOpSig pass) Bool [LIdP pass] (LHsSigType pass) + + -- | A type signature in generated code, notably the code + -- generated for record selectors. We simply record + -- the desired Id itself, replete with its name, type + -- and IdDetails. Otherwise it's just like a type + -- signature: there should be an accompanying binding + | IdSig (XIdSig pass) Id + + -- | An ordinary fixity declaration + -- + -- > infixl 8 *** + -- + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnInfix', + -- 'GHC.Parser.Annotation.AnnVal' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | FixSig (XFixSig pass) (FixitySig pass) + + -- | An inline pragma + -- + -- > {#- INLINE f #-} + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : + -- 'GHC.Parser.Annotation.AnnOpen' @'{-\# INLINE'@ and @'['@, + -- 'GHC.Parser.Annotation.AnnClose','GHC.Parser.Annotation.AnnOpen', + -- 'GHC.Parser.Annotation.AnnVal','GHC.Parser.Annotation.AnnTilde', + -- 'GHC.Parser.Annotation.AnnClose' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | InlineSig (XInlineSig pass) + (LIdP pass) -- Function name + InlinePragma -- Never defaultInlinePragma + + -- | A specialisation pragma + -- + -- > {-# SPECIALISE f :: Int -> Int #-} + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen', + -- 'GHC.Parser.Annotation.AnnOpen' @'{-\# SPECIALISE'@ and @'['@, + -- 'GHC.Parser.Annotation.AnnTilde', + -- 'GHC.Parser.Annotation.AnnVal', + -- 'GHC.Parser.Annotation.AnnClose' @']'@ and @'\#-}'@, + -- 'GHC.Parser.Annotation.AnnDcolon' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | SpecSig (XSpecSig pass) + (LIdP pass) -- Specialise a function or datatype ... + [LHsSigType pass] -- ... to these types + InlinePragma -- The pragma on SPECIALISE_INLINE form. + -- If it's just defaultInlinePragma, then we said + -- SPECIALISE, not SPECIALISE_INLINE + + -- | A specialisation pragma for instance declarations only + -- + -- > {-# SPECIALISE instance Eq [Int] #-} + -- + -- (Class tys); should be a specialisation of the + -- current instance declaration + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen', + -- 'GHC.Parser.Annotation.AnnInstance','GHC.Parser.Annotation.AnnClose' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | SpecInstSig (XSpecInstSig pass) SourceText (LHsSigType pass) + -- Note [Pragma source text] in GHC.Types.SourceText + + -- | A minimal complete definition pragma + -- + -- > {-# MINIMAL a | (b, c | (d | e)) #-} + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen', + -- 'GHC.Parser.Annotation.AnnVbar','GHC.Parser.Annotation.AnnComma', + -- 'GHC.Parser.Annotation.AnnClose' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | MinimalSig (XMinimalSig pass) + SourceText (LBooleanFormula (LIdP pass)) + -- Note [Pragma source text] in GHC.Types.SourceText + + -- | A "set cost centre" pragma for declarations + -- + -- > {-# SCC funName #-} + -- + -- or + -- + -- > {-# SCC funName "cost_centre_name" #-} + + | SCCFunSig (XSCCFunSig pass) + SourceText -- Note [Pragma source text] in GHC.Types.SourceText + (LIdP pass) -- Function name + (Maybe (XRec pass StringLiteral)) + -- | A complete match pragma + -- + -- > {-# COMPLETE C, D [:: T] #-} + -- + -- Used to inform the pattern match checker about additional + -- complete matchings which, for example, arise from pattern + -- synonym definitions. + | CompleteMatchSig (XCompleteMatchSig pass) + SourceText + (XRec pass [LIdP pass]) + (Maybe (LIdP pass)) + | XSig !(XXSig pass) + +-- | Located Fixity Signature +type LFixitySig pass = XRec pass (FixitySig pass) + +-- | Fixity Signature +data FixitySig pass = FixitySig (XFixitySig pass) [LIdP pass] Fixity + | XFixitySig !(XXFixitySig pass) + +-- | Type checker Specialisation Pragmas +-- +-- 'TcSpecPrags' conveys @SPECIALISE@ pragmas from the type checker to the desugarer +data TcSpecPrags + = IsDefaultMethod -- ^ Super-specialised: a default method should + -- be macro-expanded at every call site + | SpecPrags [LTcSpecPrag] + deriving Data + +-- | Located Type checker Specification Pragmas +type LTcSpecPrag = Located TcSpecPrag + +-- | Type checker Specification Pragma +data TcSpecPrag + = SpecPrag + Id + HsWrapper + InlinePragma + -- ^ The Id to be specialised, a wrapper that specialises the + -- polymorphic function, and inlining spec for the specialised function + deriving Data + +noSpecPrags :: TcSpecPrags +noSpecPrags = SpecPrags [] + +hasSpecPrags :: TcSpecPrags -> Bool +hasSpecPrags (SpecPrags ps) = not (null ps) +hasSpecPrags IsDefaultMethod = False + +isDefaultMethod :: TcSpecPrags -> Bool +isDefaultMethod IsDefaultMethod = True +isDefaultMethod (SpecPrags {}) = False + +isFixityLSig :: forall p. UnXRec p => LSig p -> Bool +isFixityLSig (unXRec @p -> FixSig {}) = True +isFixityLSig _ = False + +isTypeLSig :: forall p. UnXRec p => LSig p -> Bool -- Type signatures +isTypeLSig (unXRec @p -> TypeSig {}) = True +isTypeLSig (unXRec @p -> ClassOpSig {}) = True +isTypeLSig (unXRec @p -> IdSig {}) = True +isTypeLSig _ = False + +isSpecLSig :: forall p. UnXRec p => LSig p -> Bool +isSpecLSig (unXRec @p -> SpecSig {}) = True +isSpecLSig _ = False + +isSpecInstLSig :: forall p. UnXRec p => LSig p -> Bool +isSpecInstLSig (unXRec @p -> SpecInstSig {}) = True +isSpecInstLSig _ = False + +isPragLSig :: forall p. UnXRec p => LSig p -> Bool +-- Identifies pragmas +isPragLSig (unXRec @p -> SpecSig {}) = True +isPragLSig (unXRec @p -> InlineSig {}) = True +isPragLSig (unXRec @p -> SCCFunSig {}) = True +isPragLSig (unXRec @p -> CompleteMatchSig {}) = True +isPragLSig _ = False + +isInlineLSig :: forall p. UnXRec p => LSig p -> Bool +-- Identifies inline pragmas +isInlineLSig (unXRec @p -> InlineSig {}) = True +isInlineLSig _ = False + +isMinimalLSig :: forall p. UnXRec p => LSig p -> Bool +isMinimalLSig (unXRec @p -> MinimalSig {}) = True +isMinimalLSig _ = False + +isSCCFunSig :: forall p. UnXRec p => LSig p -> Bool +isSCCFunSig (unXRec @p -> SCCFunSig {}) = True +isSCCFunSig _ = False + +isCompleteMatchSig :: forall p. UnXRec p => LSig p -> Bool +isCompleteMatchSig (unXRec @p -> CompleteMatchSig {} ) = True +isCompleteMatchSig _ = False + +hsSigDoc :: Sig name -> SDoc +hsSigDoc (TypeSig {}) = text "type signature" +hsSigDoc (PatSynSig {}) = text "pattern synonym signature" +hsSigDoc (ClassOpSig _ is_deflt _ _) + | is_deflt = text "default type signature" + | otherwise = text "class method signature" +hsSigDoc (IdSig {}) = text "id signature" +hsSigDoc (SpecSig _ _ _ inl) + = ppr inl <+> text "pragma" +hsSigDoc (InlineSig _ _ prag) = ppr (inlinePragmaSpec prag) <+> text "pragma" +hsSigDoc (SpecInstSig _ src _) + = pprWithSourceText src empty <+> text "instance pragma" +hsSigDoc (FixSig {}) = text "fixity declaration" +hsSigDoc (MinimalSig {}) = text "MINIMAL pragma" +hsSigDoc (SCCFunSig {}) = text "SCC pragma" +hsSigDoc (CompleteMatchSig {}) = text "COMPLETE pragma" +hsSigDoc (XSig {}) = text "XSIG TTG extension" + +{- +************************************************************************ +* * +\subsection[PatSynBind]{A pattern synonym definition} +* * +************************************************************************ +-} + +-- | Haskell Pattern Synonym Details +type HsPatSynDetails pass = HsConDetails Void (LIdP pass) [RecordPatSynField pass] + +-- See Note [Record PatSyn Fields] +-- | Record Pattern Synonym Field +data RecordPatSynField pass + = RecordPatSynField + { recordPatSynField :: FieldOcc pass + -- ^ Field label visible in rest of the file + , recordPatSynPatVar :: LIdP pass + -- ^ Filled in by renamer, the name used internally by the pattern + } + + +{- +Note [Record PatSyn Fields] +~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Consider the following two pattern synonyms. + + pattern P x y = ([x,True], [y,'v']) + pattern Q{ x, y } =([x,True], [y,'v']) + +In P, we just have two local binders, x and y. + +In Q, we have local binders but also top-level record selectors + x :: ([Bool], [Char]) -> Bool + y :: ([Bool], [Char]) -> Char + +Both are recorded in the `RecordPatSynField`s for `x` and `y`: +* recordPatSynField: the top-level record selector +* recordPatSynPatVar: the local `x`, bound only in the RHS of the pattern synonym. + +It would make sense to support record-like syntax + + pattern Q{ x=x1, y=y1 } = ([x1,True], [y1,'v']) + +when we have a different name for the local and top-level binder, +making the distinction between the two names clear. + +-} +instance Outputable (RecordPatSynField a) where + ppr (RecordPatSynField { recordPatSynField = v }) = ppr v + + +-- | Haskell Pattern Synonym Direction +data HsPatSynDir id + = Unidirectional + | ImplicitBidirectional + | ExplicitBidirectional (MatchGroup id (LHsExpr id)) diff --git a/compiler/Language/Haskell/Syntax/Decls.hs b/compiler/Language/Haskell/Syntax/Decls.hs new file mode 100644 index 0000000000..ff65d085c7 --- /dev/null +++ b/compiler/Language/Haskell/Syntax/Decls.hs @@ -0,0 +1,1804 @@ +{-# LANGUAGE CPP #-} +{-# LANGUAGE ConstraintKinds #-} +{-# LANGUAGE DeriveDataTypeable #-} +{-# LANGUAGE DeriveTraversable #-} +{-# LANGUAGE FlexibleContexts #-} +{-# LANGUAGE FlexibleInstances #-} +{-# LANGUAGE ScopedTypeVariables #-} +{-# LANGUAGE StandaloneDeriving #-} +{-# LANGUAGE TypeApplications #-} +{-# LANGUAGE TypeFamilies #-} +{-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow] + -- in module Language.Haskell.Syntax.Extension + +{- +(c) The University of Glasgow 2006 +(c) The GRASP/AQUA Project, Glasgow University, 1992-1998 +-} + + +{-# OPTIONS_GHC -Wno-incomplete-record-updates #-} + +-- See Note [Language.Haskell.Syntax.* Hierarchy] for why not GHC.Hs.* + +-- | Abstract syntax of global declarations. +-- +-- Definitions for: @SynDecl@ and @ConDecl@, @ClassDecl@, +-- @InstDecl@, @DefaultDecl@ and @ForeignDecl@. +module Language.Haskell.Syntax.Decls ( + -- * Toplevel declarations + HsDecl(..), LHsDecl, HsDataDefn(..), HsDeriving, LHsFunDep, + HsDerivingClause(..), LHsDerivingClause, DerivClauseTys(..), LDerivClauseTys, + NewOrData(..), newOrDataToFlavour, + StandaloneKindSig(..), LStandaloneKindSig, + + -- ** Class or type declarations + TyClDecl(..), LTyClDecl, DataDeclRn(..), + TyClGroup(..), + tyClGroupTyClDecls, tyClGroupInstDecls, tyClGroupRoleDecls, + tyClGroupKindSigs, + isClassDecl, isDataDecl, isSynDecl, + isFamilyDecl, isTypeFamilyDecl, isDataFamilyDecl, + isOpenTypeFamilyInfo, isClosedTypeFamilyInfo, + countTyClDecls, + tyClDeclTyVars, + FamilyDecl(..), LFamilyDecl, + + -- ** Instance declarations + InstDecl(..), LInstDecl, FamilyInfo(..), pprFlavour, + TyFamInstDecl(..), LTyFamInstDecl, + TyFamDefltDecl, LTyFamDefltDecl, + DataFamInstDecl(..), LDataFamInstDecl, + FamEqn(..), TyFamInstEqn, LTyFamInstEqn, HsTyPats, + LClsInstDecl, ClsInstDecl(..), + + -- ** Standalone deriving declarations + DerivDecl(..), LDerivDecl, + -- ** Deriving strategies + DerivStrategy(..), LDerivStrategy, + derivStrategyName, + -- ** @RULE@ declarations + LRuleDecls,RuleDecls(..),RuleDecl(..),LRuleDecl,HsRuleRn(..), + RuleBndr(..),LRuleBndr, + collectRuleBndrSigTys, + pprFullRuleName, + -- ** @default@ declarations + DefaultDecl(..), LDefaultDecl, + -- ** Template haskell declaration splice + SpliceExplicitFlag(..), + SpliceDecl(..), LSpliceDecl, + -- ** Foreign function interface declarations + ForeignDecl(..), LForeignDecl, ForeignImport(..), ForeignExport(..), + CImportSpec(..), + -- ** Data-constructor declarations + ConDecl(..), LConDecl, + HsConDeclH98Details, HsConDeclGADTDetails(..), + -- ** Document comments + DocDecl(..), LDocDecl, docDeclDoc, + -- ** Deprecations + WarnDecl(..), LWarnDecl, + WarnDecls(..), LWarnDecls, + -- ** Annotations + AnnDecl(..), LAnnDecl, + AnnProvenance(..), annProvenanceName_maybe, + -- ** Role annotations + RoleAnnotDecl(..), LRoleAnnotDecl, + -- ** Injective type families + FamilyResultSig(..), LFamilyResultSig, InjectivityAnn(..), LInjectivityAnn, + + -- * Grouping + HsGroup(..), hsGroupInstDecls, + ) where + +-- friends: +import GHC.Prelude + +import {-# SOURCE #-} Language.Haskell.Syntax.Expr + ( HsExpr, HsSplice ) + -- Because Expr imports Decls via HsBracket + +import Language.Haskell.Syntax.Binds +import Language.Haskell.Syntax.Type +import GHC.Hs.Doc +import GHC.Core.TyCon +import GHC.Types.Basic +import GHC.Types.ForeignCall +import Language.Haskell.Syntax.Extension +import GHC.Types.Name.Set +import GHC.Types.Fixity + +-- others: +import GHC.Core.Class +import GHC.Utils.Outputable +import GHC.Utils.Misc +import GHC.Types.SrcLoc +import GHC.Types.SourceText +import GHC.Core.Type +import GHC.Unit.Module.Warnings + +import GHC.Data.Maybe +import Data.Data hiding (TyCon,Fixity, Infix) +import Data.Void + +{- +************************************************************************ +* * +\subsection[HsDecl]{Declarations} +* * +************************************************************************ +-} + +type LHsDecl p = XRec p (HsDecl p) + -- ^ When in a list this may have + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnSemi' + -- + +-- For details on above see note [Api annotations] in GHC.Parser.Annotation + +-- | A Haskell Declaration +data HsDecl p + = TyClD (XTyClD p) (TyClDecl p) -- ^ Type or Class Declaration + | InstD (XInstD p) (InstDecl p) -- ^ Instance declaration + | DerivD (XDerivD p) (DerivDecl p) -- ^ Deriving declaration + | ValD (XValD p) (HsBind p) -- ^ Value declaration + | SigD (XSigD p) (Sig p) -- ^ Signature declaration + | KindSigD (XKindSigD p) (StandaloneKindSig p) -- ^ Standalone kind signature + | DefD (XDefD p) (DefaultDecl p) -- ^ 'default' declaration + | ForD (XForD p) (ForeignDecl p) -- ^ Foreign declaration + | WarningD (XWarningD p) (WarnDecls p) -- ^ Warning declaration + | AnnD (XAnnD p) (AnnDecl p) -- ^ Annotation declaration + | RuleD (XRuleD p) (RuleDecls p) -- ^ Rule declaration + | SpliceD (XSpliceD p) (SpliceDecl p) -- ^ Splice declaration + -- (Includes quasi-quotes) + | DocD (XDocD p) (DocDecl) -- ^ Documentation comment declaration + | RoleAnnotD (XRoleAnnotD p) (RoleAnnotDecl p) -- ^Role annotation declaration + | XHsDecl !(XXHsDecl p) + +{- +Note [Top-level fixity signatures in an HsGroup] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +An `HsGroup p` stores every top-level fixity declarations in one of two places: + +1. hs_fixds :: [LFixitySig p] + + This stores fixity signatures for top-level declarations (e.g., functions, + data constructors, classes, type families, etc.) as well as fixity + signatures for class methods written outside of the class, as in this + example: + + infixl 4 `m1` + class C1 a where + m1 :: a -> a -> a + +2. hs_tyclds :: [TyClGroup p] + + Each type class can be found in a TyClDecl inside a TyClGroup, and that + TyClDecl stores the fixity signatures for its methods written inside of the + class, as in this example: + + class C2 a where + infixl 4 `m2` + m2 :: a -> a -> a + +The story for fixity signatures for class methods is made slightly complicated +by the fact that they can appear both inside and outside of the class itself, +and both forms of fixity signatures are considered top-level. This matters +in `GHC.Rename.Module.rnSrcDecls`, which must create a fixity environment out +of all top-level fixity signatures before doing anything else. Therefore, +`rnSrcDecls` must be aware of both (1) and (2) above. The +`hsGroupTopLevelFixitySigs` function is responsible for collecting this +information from an `HsGroup`. + +One might wonder why we even bother separating top-level fixity signatures +into two places at all. That is, why not just take the fixity signatures +from `hs_tyclds` and put them into `hs_fixds` so that they are all in one +location? This ends up causing problems for `GHC.HsToCore.Quote.repTopDs`, +which translates each fixity signature in `hs_fixds` and `hs_tyclds` into a +Template Haskell `Dec`. If there are any duplicate signatures between the two +fields, this will result in an error (#17608). +-} + +-- | Haskell Group +-- +-- A 'HsDecl' is categorised into a 'HsGroup' before being +-- fed to the renamer. +data HsGroup p + = HsGroup { + hs_ext :: XCHsGroup p, + hs_valds :: HsValBinds p, + hs_splcds :: [LSpliceDecl p], + + hs_tyclds :: [TyClGroup p], + -- A list of mutually-recursive groups; + -- This includes `InstDecl`s as well; + -- Parser generates a singleton list; + -- renamer does dependency analysis + + hs_derivds :: [LDerivDecl p], + + hs_fixds :: [LFixitySig p], + -- A list of fixity signatures defined for top-level + -- declarations and class methods (defined outside of the class + -- itself). + -- See Note [Top-level fixity signatures in an HsGroup] + + hs_defds :: [LDefaultDecl p], + hs_fords :: [LForeignDecl p], + hs_warnds :: [LWarnDecls p], + hs_annds :: [LAnnDecl p], + hs_ruleds :: [LRuleDecls p], + + hs_docs :: [LDocDecl] + } + | XHsGroup !(XXHsGroup p) + + +hsGroupInstDecls :: HsGroup id -> [LInstDecl id] +hsGroupInstDecls = (=<<) group_instds . hs_tyclds + +-- | Located Splice Declaration +type LSpliceDecl pass = XRec pass (SpliceDecl pass) + +-- | Splice Declaration +data SpliceDecl p + = SpliceDecl -- Top level splice + (XSpliceDecl p) + (XRec p (HsSplice p)) + SpliceExplicitFlag + | XSpliceDecl !(XXSpliceDecl p) + +{- +************************************************************************ +* * + Type and class declarations +* * +************************************************************************ + +Note [The Naming story] +~~~~~~~~~~~~~~~~~~~~~~~ +Here is the story about the implicit names that go with type, class, +and instance decls. It's a bit tricky, so pay attention! + +"Implicit" (or "system") binders +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + Each data type decl defines + a worker name for each constructor + to-T and from-T convertors + Each class decl defines + a tycon for the class + a data constructor for that tycon + the worker for that constructor + a selector for each superclass + +All have occurrence names that are derived uniquely from their parent +declaration. + +None of these get separate definitions in an interface file; they are +fully defined by the data or class decl. But they may *occur* in +interface files, of course. Any such occurrence must haul in the +relevant type or class decl. + +Plan of attack: + - Ensure they "point to" the parent data/class decl + when loading that decl from an interface file + (See RnHiFiles.getSysBinders) + + - When typechecking the decl, we build the implicit TyCons and Ids. + When doing so we look them up in the name cache (GHC.Rename.Env.lookupSysName), + to ensure correct module and provenance is set + +These are the two places that we have to conjure up the magic derived +names. (The actual magic is in GHC.Types.Name.Occurrence.mkWorkerOcc, etc.) + +Default methods +~~~~~~~~~~~~~~~ + - Occurrence name is derived uniquely from the method name + E.g. $dmmax + + - If there is a default method name at all, it's recorded in + the ClassOpSig (in GHC.Hs.Binds), in the DefMethInfo field. + (DefMethInfo is defined in GHC.Core.Class) + +Source-code class decls and interface-code class decls are treated subtly +differently, which has given me a great deal of confusion over the years. +Here's the deal. (We distinguish the two cases because source-code decls +have (Just binds) in the tcdMeths field, whereas interface decls have Nothing. + +In *source-code* class declarations: + + - When parsing, every ClassOpSig gets a DefMeth with a suitable RdrName + This is done by GHC.Parser.PostProcess.mkClassOpSigDM + + - The renamer renames it to a Name + + - During typechecking, we generate a binding for each $dm for + which there's a programmer-supplied default method: + class Foo a where + op1 :: <type> + op2 :: <type> + op1 = ... + We generate a binding for $dmop1 but not for $dmop2. + The Class for Foo has a Nothing for op2 and + a Just ($dm_op1, VanillaDM) for op1. + The Name for $dmop2 is simply discarded. + +In *interface-file* class declarations: + - When parsing, we see if there's an explicit programmer-supplied default method + because there's an '=' sign to indicate it: + class Foo a where + op1 = :: <type> -- NB the '=' + op2 :: <type> + We use this info to generate a DefMeth with a suitable RdrName for op1, + and a NoDefMeth for op2 + - The interface file has a separate definition for $dmop1, with unfolding etc. + - The renamer renames it to a Name. + - The renamer treats $dmop1 as a free variable of the declaration, so that + the binding for $dmop1 will be sucked in. (See RnHsSyn.tyClDeclFVs) + This doesn't happen for source code class decls, because they *bind* the default method. + +Dictionary functions +~~~~~~~~~~~~~~~~~~~~ +Each instance declaration gives rise to one dictionary function binding. + +The type checker makes up new source-code instance declarations +(e.g. from 'deriving' or generic default methods --- see +GHC.Tc.TyCl.Instance.tcInstDecls1). So we can't generate the names for +dictionary functions in advance (we don't know how many we need). + +On the other hand for interface-file instance declarations, the decl +specifies the name of the dictionary function, and it has a binding elsewhere +in the interface file: + instance {Eq Int} = dEqInt + dEqInt :: {Eq Int} <pragma info> + +So again we treat source code and interface file code slightly differently. + +Source code: + - Source code instance decls have a Nothing in the (Maybe name) field + (see data InstDecl below) + + - The typechecker makes up a Local name for the dict fun for any source-code + instance decl, whether it comes from a source-code instance decl, or whether + the instance decl is derived from some other construct (e.g. 'deriving'). + + - The occurrence name it chooses is derived from the instance decl (just for + documentation really) --- e.g. dNumInt. Two dict funs may share a common + occurrence name, but will have different uniques. E.g. + instance Foo [Int] where ... + instance Foo [Bool] where ... + These might both be dFooList + + - The CoreTidy phase externalises the name, and ensures the occurrence name is + unique (this isn't special to dict funs). So we'd get dFooList and dFooList1. + + - We can take this relaxed approach (changing the occurrence name later) + because dict fun Ids are not captured in a TyCon or Class (unlike default + methods, say). Instead, they are kept separately in the InstEnv. This + makes it easy to adjust them after compiling a module. (Once we've finished + compiling that module, they don't change any more.) + + +Interface file code: + - The instance decl gives the dict fun name, so the InstDecl has a (Just name) + in the (Maybe name) field. + + - RnHsSyn.instDeclFVs treats the dict fun name as free in the decl, so that we + suck in the dfun binding +-} + +-- | Located Declaration of a Type or Class +type LTyClDecl pass = XRec pass (TyClDecl pass) + +-- | A type or class declaration. +data TyClDecl pass + = -- | @type/data family T :: *->*@ + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnType', + -- 'GHC.Parser.Annotation.AnnData', + -- 'GHC.Parser.Annotation.AnnFamily','GHC.Parser.Annotation.AnnDcolon', + -- 'GHC.Parser.Annotation.AnnWhere','GHC.Parser.Annotation.AnnOpenP', + -- 'GHC.Parser.Annotation.AnnDcolon','GHC.Parser.Annotation.AnnCloseP', + -- 'GHC.Parser.Annotation.AnnEqual','GHC.Parser.Annotation.AnnRarrow', + -- 'GHC.Parser.Annotation.AnnVbar' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + FamDecl { tcdFExt :: XFamDecl pass, tcdFam :: FamilyDecl pass } + + | -- | @type@ declaration + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnType', + -- 'GHC.Parser.Annotation.AnnEqual', + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + SynDecl { tcdSExt :: XSynDecl pass -- ^ Post renameer, FVs + , tcdLName :: LIdP pass -- ^ Type constructor + , tcdTyVars :: LHsQTyVars pass -- ^ Type variables; for an + -- associated type these + -- include outer binders + , tcdFixity :: LexicalFixity -- ^ Fixity used in the declaration + , tcdRhs :: LHsType pass } -- ^ RHS of type declaration + + | -- | @data@ declaration + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnData', + -- 'GHC.Parser.Annotation.AnnFamily', + -- 'GHC.Parser.Annotation.AnnNewType', + -- 'GHC.Parser.Annotation.AnnNewType','GHC.Parser.Annotation.AnnDcolon' + -- 'GHC.Parser.Annotation.AnnWhere', + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + DataDecl { tcdDExt :: XDataDecl pass -- ^ Post renamer, CUSK flag, FVs + , tcdLName :: LIdP pass -- ^ Type constructor + , tcdTyVars :: LHsQTyVars pass -- ^ Type variables + -- See Note [TyVar binders for associated declarations] + , tcdFixity :: LexicalFixity -- ^ Fixity used in the declaration + , tcdDataDefn :: HsDataDefn pass } + + | ClassDecl { tcdCExt :: XClassDecl pass, -- ^ Post renamer, FVs + tcdCtxt :: LHsContext pass, -- ^ Context... + tcdLName :: LIdP pass, -- ^ Name of the class + tcdTyVars :: LHsQTyVars pass, -- ^ Class type variables + tcdFixity :: LexicalFixity, -- ^ Fixity used in the declaration + tcdFDs :: [LHsFunDep pass], -- ^ Functional deps + tcdSigs :: [LSig pass], -- ^ Methods' signatures + tcdMeths :: LHsBinds pass, -- ^ Default methods + tcdATs :: [LFamilyDecl pass], -- ^ Associated types; + tcdATDefs :: [LTyFamDefltDecl pass], -- ^ Associated type defaults + tcdDocs :: [LDocDecl] -- ^ Haddock docs + } + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnClass', + -- 'GHC.Parser.Annotation.AnnWhere','GHC.Parser.Annotation.AnnOpen', + -- 'GHC.Parser.Annotation.AnnClose' + -- - The tcdFDs will have 'GHC.Parser.Annotation.AnnVbar', + -- 'GHC.Parser.Annotation.AnnComma' + -- 'GHC.Parser.Annotation.AnnRarrow' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | XTyClDecl !(XXTyClDecl pass) + +type LHsFunDep pass = XRec pass (FunDep (LIdP pass)) + +data DataDeclRn = DataDeclRn + { tcdDataCusk :: Bool -- ^ does this have a CUSK? + -- See Note [CUSKs: complete user-supplied kind signatures] + , tcdFVs :: NameSet } + deriving Data + +{- Note [TyVar binders for associated decls] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +For an /associated/ data, newtype, or type-family decl, the LHsQTyVars +/includes/ outer binders. For example + class T a where + data D a c + type F a b :: * + type F a b = a -> a +Here the data decl for 'D', and type-family decl for 'F', both include 'a' +in their LHsQTyVars (tcdTyVars and fdTyVars resp). + +Ditto any implicit binders in the hsq_implicit field of the LHSQTyVars. + +The idea is that the associated type is really a top-level decl in its +own right. However we are careful to use the same name 'a', so that +we can match things up. + +c.f. Note [Associated type tyvar names] in GHC.Core.Class + Note [Family instance declaration binders] +-} + +{- Note [Class LayoutInfo] +~~~~~~~~~~~~~~~~~~~~~~~~~~ +The LayoutInfo is used to associate Haddock comments with parts of the declaration. +Compare the following examples: + + class C a where + f :: a -> Int + -- ^ comment on f + + class C a where + f :: a -> Int + -- ^ comment on C + +Notice how "comment on f" and "comment on C" differ only by indentation level. +Thus we have to record the indentation level of the class declarations. + +See also Note [Adding Haddock comments to the syntax tree] in GHC.Parser.PostProcess.Haddock +-} + +-- Simple classifiers for TyClDecl +-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +-- | @True@ <=> argument is a @data@\/@newtype@ +-- declaration. +isDataDecl :: TyClDecl pass -> Bool +isDataDecl (DataDecl {}) = True +isDataDecl _other = False + +-- | type or type instance declaration +isSynDecl :: TyClDecl pass -> Bool +isSynDecl (SynDecl {}) = True +isSynDecl _other = False + +-- | type class +isClassDecl :: TyClDecl pass -> Bool +isClassDecl (ClassDecl {}) = True +isClassDecl _ = False + +-- | type/data family declaration +isFamilyDecl :: TyClDecl pass -> Bool +isFamilyDecl (FamDecl {}) = True +isFamilyDecl _other = False + +-- | type family declaration +isTypeFamilyDecl :: TyClDecl pass -> Bool +isTypeFamilyDecl (FamDecl _ (FamilyDecl { fdInfo = info })) = case info of + OpenTypeFamily -> True + ClosedTypeFamily {} -> True + _ -> False +isTypeFamilyDecl _ = False + +-- | open type family info +isOpenTypeFamilyInfo :: FamilyInfo pass -> Bool +isOpenTypeFamilyInfo OpenTypeFamily = True +isOpenTypeFamilyInfo _ = False + +-- | closed type family info +isClosedTypeFamilyInfo :: FamilyInfo pass -> Bool +isClosedTypeFamilyInfo (ClosedTypeFamily {}) = True +isClosedTypeFamilyInfo _ = False + +-- | data family declaration +isDataFamilyDecl :: TyClDecl pass -> Bool +isDataFamilyDecl (FamDecl _ (FamilyDecl { fdInfo = DataFamily })) = True +isDataFamilyDecl _other = False + +-- Dealing with names + +tyClDeclTyVars :: TyClDecl pass -> LHsQTyVars pass +tyClDeclTyVars (FamDecl { tcdFam = FamilyDecl { fdTyVars = tvs } }) = tvs +tyClDeclTyVars d = tcdTyVars d + +countTyClDecls :: [TyClDecl pass] -> (Int, Int, Int, Int, Int) + -- class, synonym decls, data, newtype, family decls +countTyClDecls decls + = (count isClassDecl decls, + count isSynDecl decls, -- excluding... + count isDataTy decls, -- ...family... + count isNewTy decls, -- ...instances + count isFamilyDecl decls) + where + isDataTy DataDecl{ tcdDataDefn = HsDataDefn { dd_ND = DataType } } = True + isDataTy _ = False + + isNewTy DataDecl{ tcdDataDefn = HsDataDefn { dd_ND = NewType } } = True + isNewTy _ = False + + +{- Note [CUSKs: complete user-supplied kind signatures] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +We kind-check declarations differently if they have a complete, user-supplied +kind signature (CUSK). This is because we can safely generalise a CUSKed +declaration before checking all of the others, supporting polymorphic recursion. +See https://gitlab.haskell.org/ghc/ghc/wikis/ghc-kinds/kind-inference#proposed-new-strategy +and #9200 for lots of discussion of how we got here. + +The detection of CUSKs is enabled by the -XCUSKs extension, switched on by default. +Under -XNoCUSKs, all declarations are treated as if they have no CUSK. +See https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0036-kind-signatures.rst + +PRINCIPLE: + a type declaration has a CUSK iff we could produce a separate kind signature + for it, just like a type signature for a function, + looking only at the header of the declaration. + +Examples: + * data T1 (a :: *->*) (b :: *) = .... + -- Has CUSK; equivalant to T1 :: (*->*) -> * -> * + + * data T2 a b = ... + -- No CUSK; we do not want to guess T2 :: * -> * -> * + -- because the full decl might be data T a b = MkT (a b) + + * data T3 (a :: k -> *) (b :: *) = ... + -- CUSK; equivalent to T3 :: (k -> *) -> * -> * + -- We lexically generalise over k to get + -- T3 :: forall k. (k -> *) -> * -> * + -- The generalisation is here is purely lexical, just like + -- f3 :: a -> a + -- means + -- f3 :: forall a. a -> a + + * data T4 (a :: j k) = ... + -- CUSK; equivalent to T4 :: j k -> * + -- which we lexically generalise to T4 :: forall j k. j k -> * + -- and then, if PolyKinds is on, we further generalise to + -- T4 :: forall kk (j :: kk -> *) (k :: kk). j k -> * + -- Again this is exactly like what happens as the term level + -- when you write + -- f4 :: forall a b. a b -> Int + +NOTE THAT + * A CUSK does /not/ mean that everything about the kind signature is + fully specified by the user. Look at T4 and f4: we had to do kind + inference to figure out the kind-quantification. But in both cases + (T4 and f4) that inference is done looking /only/ at the header of T4 + (or signature for f4), not at the definition thereof. + + * The CUSK completely fixes the kind of the type constructor, forever. + + * The precise rules, for each declaration form, for whether a declaration + has a CUSK are given in the user manual section "Complete user-supplied + kind signatures and polymorphic recursion". But they simply implement + PRINCIPLE above. + + * Open type families are interesting: + type family T5 a b :: * + There simply /is/ no accompanying declaration, so that info is all + we'll ever get. So we it has a CUSK by definition, and we default + any un-fixed kind variables to *. + + * Associated types are a bit tricker: + class C6 a where + type family T6 a b :: * + op :: a Int -> Int + Here C6 does not have a CUSK (in fact we ultimately discover that + a :: * -> *). And hence neither does T6, the associated family, + because we can't fix its kind until we have settled C6. Another + way to say it: unlike a top-level, we /may/ discover more about + a's kind from C6's definition. + + * A data definition with a top-level :: must explicitly bind all + kind variables to the right of the ::. See test + dependent/should_compile/KindLevels, which requires this + case. (Naturally, any kind variable mentioned before the :: should + not be bound after it.) + + This last point is much more debatable than the others; see + #15142 comment:22 + + Because this is fiddly to check, there is a field in the DataDeclRn + structure (included in a DataDecl after the renamer) that stores whether + or not the declaration has a CUSK. +-} + + +{- ********************************************************************* +* * + TyClGroup + Strongly connected components of + type, class, instance, and role declarations +* * +********************************************************************* -} + +{- Note [TyClGroups and dependency analysis] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +A TyClGroup represents a strongly connected components of type/class/instance +decls, together with the role annotations for the type/class declarations. + +The hs_tyclds :: [TyClGroup] field of a HsGroup is a dependency-order +sequence of strongly-connected components. + +Invariants + * The type and class declarations, group_tyclds, may depend on each + other, or earlier TyClGroups, but not on later ones + + * The role annotations, group_roles, are role-annotations for some or + all of the types and classes in group_tyclds (only). + + * The instance declarations, group_instds, may (and usually will) + depend on group_tyclds, or on earlier TyClGroups, but not on later + ones. + +See Note [Dependency analysis of type, class, and instance decls] +in GHC.Rename.Module for more info. +-} + +-- | Type or Class Group +data TyClGroup pass -- See Note [TyClGroups and dependency analysis] + = TyClGroup { group_ext :: XCTyClGroup pass + , group_tyclds :: [LTyClDecl pass] + , group_roles :: [LRoleAnnotDecl pass] + , group_kisigs :: [LStandaloneKindSig pass] + , group_instds :: [LInstDecl pass] } + | XTyClGroup !(XXTyClGroup pass) + + +tyClGroupTyClDecls :: [TyClGroup pass] -> [LTyClDecl pass] +tyClGroupTyClDecls = concatMap group_tyclds + +tyClGroupInstDecls :: [TyClGroup pass] -> [LInstDecl pass] +tyClGroupInstDecls = concatMap group_instds + +tyClGroupRoleDecls :: [TyClGroup pass] -> [LRoleAnnotDecl pass] +tyClGroupRoleDecls = concatMap group_roles + +tyClGroupKindSigs :: [TyClGroup pass] -> [LStandaloneKindSig pass] +tyClGroupKindSigs = concatMap group_kisigs + + +{- ********************************************************************* +* * + Data and type family declarations +* * +********************************************************************* -} + +{- Note [FamilyResultSig] +~~~~~~~~~~~~~~~~~~~~~~~~~ + +This data type represents the return signature of a type family. Possible +values are: + + * NoSig - the user supplied no return signature: + type family Id a where ... + + * KindSig - the user supplied the return kind: + type family Id a :: * where ... + + * TyVarSig - user named the result with a type variable and possibly + provided a kind signature for that variable: + type family Id a = r where ... + type family Id a = (r :: *) where ... + + Naming result of a type family is required if we want to provide + injectivity annotation for a type family: + type family Id a = r | r -> a where ... + +See also: Note [Injectivity annotation] + +Note [Injectivity annotation] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +A user can declare a type family to be injective: + + type family Id a = r | r -> a where ... + + * The part after the "|" is called "injectivity annotation". + * "r -> a" part is called "injectivity condition"; at the moment terms + "injectivity annotation" and "injectivity condition" are synonymous + because we only allow a single injectivity condition. + * "r" is the "LHS of injectivity condition". LHS can only contain the + variable naming the result of a type family. + + * "a" is the "RHS of injectivity condition". RHS contains space-separated + type and kind variables representing the arguments of a type + family. Variables can be omitted if a type family is not injective in + these arguments. Example: + type family Foo a b c = d | d -> a c where ... + +Note that: + (a) naming of type family result is required to provide injectivity + annotation + (b) for associated types if the result was named then injectivity annotation + is mandatory. Otherwise result type variable is indistinguishable from + associated type default. + +It is possible that in the future this syntax will be extended to support +more complicated injectivity annotations. For example we could declare that +if we know the result of Plus and one of its arguments we can determine the +other argument: + + type family Plus a b = (r :: Nat) | r a -> b, r b -> a where ... + +Here injectivity annotation would consist of two comma-separated injectivity +conditions. + +See also Note [Injective type families] in GHC.Core.TyCon +-} + +-- | Located type Family Result Signature +type LFamilyResultSig pass = XRec pass (FamilyResultSig pass) + +-- | type Family Result Signature +data FamilyResultSig pass = -- see Note [FamilyResultSig] + NoSig (XNoSig pass) + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | KindSig (XCKindSig pass) (LHsKind pass) + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : + -- 'GHC.Parser.Annotation.AnnOpenP','GHC.Parser.Annotation.AnnDcolon', + -- 'GHC.Parser.Annotation.AnnCloseP' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | TyVarSig (XTyVarSig pass) (LHsTyVarBndr () pass) + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : + -- 'GHC.Parser.Annotation.AnnOpenP','GHC.Parser.Annotation.AnnDcolon', + -- 'GHC.Parser.Annotation.AnnCloseP', 'GHC.Parser.Annotation.AnnEqual' + | XFamilyResultSig !(XXFamilyResultSig pass) + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + +-- | Located type Family Declaration +type LFamilyDecl pass = XRec pass (FamilyDecl pass) + +-- | type Family Declaration +data FamilyDecl pass = FamilyDecl + { fdExt :: XCFamilyDecl pass + , fdInfo :: FamilyInfo pass -- type/data, closed/open + , fdLName :: LIdP pass -- type constructor + , fdTyVars :: LHsQTyVars pass -- type variables + -- See Note [TyVar binders for associated declarations] + , fdFixity :: LexicalFixity -- Fixity used in the declaration + , fdResultSig :: LFamilyResultSig pass -- result signature + , fdInjectivityAnn :: Maybe (LInjectivityAnn pass) -- optional injectivity ann + } + | XFamilyDecl !(XXFamilyDecl pass) + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnType', + -- 'GHC.Parser.Annotation.AnnData', 'GHC.Parser.Annotation.AnnFamily', + -- 'GHC.Parser.Annotation.AnnWhere', 'GHC.Parser.Annotation.AnnOpenP', + -- 'GHC.Parser.Annotation.AnnDcolon', 'GHC.Parser.Annotation.AnnCloseP', + -- 'GHC.Parser.Annotation.AnnEqual', 'GHC.Parser.Annotation.AnnRarrow', + -- 'GHC.Parser.Annotation.AnnVbar' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + +-- | Located Injectivity Annotation +type LInjectivityAnn pass = XRec pass (InjectivityAnn pass) + +-- | If the user supplied an injectivity annotation it is represented using +-- InjectivityAnn. At the moment this is a single injectivity condition - see +-- Note [Injectivity annotation]. `Located name` stores the LHS of injectivity +-- condition. `[Located name]` stores the RHS of injectivity condition. Example: +-- +-- type family Foo a b c = r | r -> a c where ... +-- +-- This will be represented as "InjectivityAnn `r` [`a`, `c`]" +data InjectivityAnn pass + = InjectivityAnn (LIdP pass) [LIdP pass] + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : + -- 'GHC.Parser.Annotation.AnnRarrow', 'GHC.Parser.Annotation.AnnVbar' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + +data FamilyInfo pass + = DataFamily + | OpenTypeFamily + -- | 'Nothing' if we're in an hs-boot file and the user + -- said "type family Foo x where .." + | ClosedTypeFamily (Maybe [LTyFamInstEqn pass]) + + +------------- Pretty printing FamilyDecls ----------- + +pprFlavour :: FamilyInfo pass -> SDoc +pprFlavour DataFamily = text "data" +pprFlavour OpenTypeFamily = text "type" +pprFlavour (ClosedTypeFamily {}) = text "type" + +instance Outputable (FamilyInfo pass) where + ppr info = pprFlavour info <+> text "family" + + + +{- ********************************************************************* +* * + Data types and data constructors +* * +********************************************************************* -} + +-- | Haskell Data type Definition +data HsDataDefn pass -- The payload of a data type defn + -- Used *both* for vanilla data declarations, + -- *and* for data family instances + = -- | Declares a data type or newtype, giving its constructors + -- @ + -- data/newtype T a = <constrs> + -- data/newtype instance T [a] = <constrs> + -- @ + HsDataDefn { dd_ext :: XCHsDataDefn pass, + dd_ND :: NewOrData, + dd_ctxt :: LHsContext pass, -- ^ Context + dd_cType :: Maybe (XRec pass CType), + dd_kindSig:: Maybe (LHsKind pass), + -- ^ Optional kind signature. + -- + -- @(Just k)@ for a GADT-style @data@, + -- or @data instance@ decl, with explicit kind sig + -- + -- Always @Nothing@ for H98-syntax decls + + dd_cons :: [LConDecl pass], + -- ^ Data constructors + -- + -- For @data T a = T1 | T2 a@ + -- the 'LConDecl's all have 'ConDeclH98'. + -- For @data T a where { T1 :: T a }@ + -- the 'LConDecls' all have 'ConDeclGADT'. + + dd_derivs :: HsDeriving pass -- ^ Optional 'deriving' clause + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + } + | XHsDataDefn !(XXHsDataDefn pass) + +-- | Haskell Deriving clause +type HsDeriving pass = XRec pass [LHsDerivingClause pass] + -- ^ The optional @deriving@ clauses of a data declaration. "Clauses" is + -- plural because one can specify multiple deriving clauses using the + -- @-XDerivingStrategies@ language extension. + -- + -- The list of 'LHsDerivingClause's corresponds to exactly what the user + -- requested to derive, in order. If no deriving clauses were specified, + -- the list is empty. + +type LHsDerivingClause pass = XRec pass (HsDerivingClause pass) + +-- | A single @deriving@ clause of a data declaration. +-- +-- - 'GHC.Parser.Annotation.AnnKeywordId' : +-- 'GHC.Parser.Annotation.AnnDeriving', 'GHC.Parser.Annotation.AnnStock', +-- 'GHC.Parser.Annotation.AnnAnyClass', 'Api.AnnNewtype', +-- 'GHC.Parser.Annotation.AnnOpen','GHC.Parser.Annotation.AnnClose' +data HsDerivingClause pass + -- See Note [Deriving strategies] in GHC.Tc.Deriv + = HsDerivingClause + { deriv_clause_ext :: XCHsDerivingClause pass + , deriv_clause_strategy :: Maybe (LDerivStrategy pass) + -- ^ The user-specified strategy (if any) to use when deriving + -- 'deriv_clause_tys'. + , deriv_clause_tys :: LDerivClauseTys pass + -- ^ The types to derive. + } + | XHsDerivingClause !(XXHsDerivingClause pass) + +type LDerivClauseTys pass = XRec pass (DerivClauseTys pass) + +-- | The types mentioned in a single @deriving@ clause. This can come in two +-- forms, 'DctSingle' or 'DctMulti', depending on whether the types are +-- surrounded by enclosing parentheses or not. These parentheses are +-- semantically differnt than 'HsParTy'. For example, @deriving ()@ means +-- \"derive zero classes\" rather than \"derive an instance of the 0-tuple\". +-- +-- 'DerivClauseTys' use 'LHsSigType' because @deriving@ clauses can mention +-- type variables that aren't bound by the datatype, e.g. +-- +-- > data T b = ... deriving (C [a]) +-- +-- should produce a derived instance for @C [a] (T b)@. +data DerivClauseTys pass + = -- | A @deriving@ clause with a single type. Moreover, that type can only + -- be a type constructor without any arguments. + -- + -- Example: @deriving Eq@ + DctSingle (XDctSingle pass) (LHsSigType pass) + + -- | A @deriving@ clause with a comma-separated list of types, surrounded + -- by enclosing parentheses. + -- + -- Example: @deriving (Eq, C a)@ + | DctMulti (XDctMulti pass) [LHsSigType pass] + + | XDerivClauseTys !(XXDerivClauseTys pass) + +-- | Located Standalone Kind Signature +type LStandaloneKindSig pass = XRec pass (StandaloneKindSig pass) + +data StandaloneKindSig pass + = StandaloneKindSig (XStandaloneKindSig pass) + (LIdP pass) -- Why a single binder? See #16754 + (LHsSigType pass) -- Why not LHsSigWcType? See Note [Wildcards in standalone kind signatures] + | XStandaloneKindSig !(XXStandaloneKindSig pass) + +{- Note [Wildcards in standalone kind signatures] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Standalone kind signatures enable polymorphic recursion, and it is unclear how +to reconcile this with partial type signatures, so we disallow wildcards in +them. + +We reject wildcards in 'rnStandaloneKindSignature' by returning False for +'StandaloneKindSigCtx' in 'wildCardsAllowed'. + +The alternative design is to have special treatment for partial standalone kind +signatures, much like we have special treatment for partial type signatures in +terms. However, partial standalone kind signatures are not a proper replacement +for CUSKs, so this would be a separate feature. +-} + +data NewOrData + = NewType -- ^ @newtype Blah ...@ + | DataType -- ^ @data Blah ...@ + deriving( Eq, Data ) -- Needed because Demand derives Eq + +-- | Convert a 'NewOrData' to a 'TyConFlavour' +newOrDataToFlavour :: NewOrData -> TyConFlavour +newOrDataToFlavour NewType = NewtypeFlavour +newOrDataToFlavour DataType = DataTypeFlavour + + +-- | Located data Constructor Declaration +type LConDecl pass = XRec pass (ConDecl pass) + -- ^ May have 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnSemi' when + -- in a GADT constructor list + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + +-- | +-- +-- @ +-- data T b = forall a. Eq a => MkT a b +-- MkT :: forall b a. Eq a => MkT a b +-- +-- data T b where +-- MkT1 :: Int -> T Int +-- +-- data T = Int `MkT` Int +-- | MkT2 +-- +-- data T a where +-- Int `MkT` Int :: T Int +-- @ +-- +-- - 'GHC.Parser.Annotation.AnnKeywordId's : 'GHC.Parser.Annotation.AnnOpen', +-- 'GHC.Parser.Annotation.AnnDotdot','GHC.Parser.Annotation.AnnCLose', +-- 'GHC.Parser.Annotation.AnnEqual','GHC.Parser.Annotation.AnnVbar', +-- 'GHC.Parser.Annotation.AnnDarrow','GHC.Parser.Annotation.AnnDarrow', +-- 'GHC.Parser.Annotation.AnnForall','GHC.Parser.Annotation.AnnDot' + +-- For details on above see note [Api annotations] in GHC.Parser.Annotation + +-- | data Constructor Declaration +data ConDecl pass + = ConDeclGADT + { con_g_ext :: XConDeclGADT pass + , con_names :: [LIdP pass] + + -- The following fields describe the type after the '::' + -- See Note [GADT abstract syntax] + , con_bndrs :: XRec pass (HsOuterSigTyVarBndrs pass) + -- ^ The outermost type variable binders, be they explicit or implicit. + -- The 'XRec' is used to anchor API annotations, AnnForall and AnnDot. + , con_mb_cxt :: Maybe (LHsContext pass) -- ^ User-written context (if any) + , con_g_args :: HsConDeclGADTDetails pass -- ^ Arguments; never infix + , con_res_ty :: LHsType pass -- ^ Result type + + , con_doc :: Maybe LHsDocString + -- ^ A possible Haddock comment. + } + + | ConDeclH98 + { con_ext :: XConDeclH98 pass + , con_name :: LIdP pass + + , con_forall :: XRec pass Bool + -- ^ True <=> explicit user-written forall + -- e.g. data T a = forall b. MkT b (b->a) + -- con_ex_tvs = {b} + -- False => con_ex_tvs is empty + , con_ex_tvs :: [LHsTyVarBndr Specificity pass] -- ^ Existentials only + , con_mb_cxt :: Maybe (LHsContext pass) -- ^ User-written context (if any) + , con_args :: HsConDeclH98Details pass -- ^ Arguments; can be infix + + , con_doc :: Maybe LHsDocString + -- ^ A possible Haddock comment. + } + | XConDecl !(XXConDecl pass) + +{- Note [GADT abstract syntax] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +The types of both forms of GADT constructors are very structured, as they +must consist of the quantified type variables (if provided), followed by the +context (if provided), followed by the argument types (if provided), followed +by the result type. (See "Wrinkle: No nested foralls or contexts" below for +more discussion on the restrictions imposed here.) As a result, instead of +storing the type of a GADT constructor as a single LHsType, we split it up +into its constituent components for easier access. + +There are two broad ways to classify GADT constructors: + +* Record-syntax constructors. For example: + + data T a where + K :: forall a. Ord a => { x :: [a], ... } -> T a + +* Prefix constructors, which do not use record syntax. For example: + + data T a where + K :: forall a. Ord a => [a] -> ... -> T a + +This distinction is recorded in the `con_args :: HsConDetails pass`, which +tracks if we're dealing with a RecCon or PrefixCon. It is easy to distinguish +the two in the AST since record GADT constructors use HsRecTy. This distinction +is made in GHC.Parser.PostProcess.mkGadtDecl. + +It is worth elaborating a bit more on the process of splitting the argument +types of a GADT constructor, since there are some non-obvious details involved. +While splitting the argument types of a record GADT constructor is easy (they +are stored in an HsRecTy), splitting the arguments of a prefix GADT constructor +is trickier. The basic idea is that we must split along the outermost function +arrows ((->) and (%1 ->)) in the type, which GHC.Hs.Type.splitHsFunType +accomplishes. But what about type operators? Consider: + + C :: a :*: b -> a :*: b -> a :+: b + +This could parse in many different ways depending on the precedences of each +type operator. In particular, if (:*:) were to have lower precedence than (->), +then it could very well parse like this: + + a :*: ((b -> a) :*: ((b -> a) :+: b))) + +This would give the false impression that the whole type is part of one large +return type, with no arguments. Note that we do not fully resolve the exact +precedences of each user-defined type operator until the renamer, so this a +more difficult task for the parser. + +Fortunately, there is no risk of the above happening. GHC's parser gives +special treatment to function arrows, and as a result, they are always parsed +with a lower precedence than any other type operator. As a result, the type +above is actually parsed like this: + + (a :*: b) -> ((a :*: b) -> (a :+: b)) + +While we won't know the exact precedences of (:*:) and (:+:) until the renamer, +all we are concerned about in the parser is identifying the overall shape of +the argument and result types, which we can accomplish by piggybacking on the +special treatment given to function arrows. In a future where function arrows +aren't given special status in the parser, we will likely have to modify +GHC.Parser.PostProcess.mkHsOpTyPV to preserve this trick. + +----- +-- Wrinkle: No nested foralls or contexts +----- + +GADT constructors provide some freedom to change the order of foralls in their +types (see Note [DataCon user type variable binders] in GHC.Core.DataCon), but +this freedom is still limited. GADTs still require that all quantification +occurs "prenex". That is, any explicitly quantified type variables must occur +at the front of the GADT type, followed by any contexts, followed by the body of +the GADT type, in precisely that order. For instance: + + data T where + MkT1 :: forall a b. (Eq a, Eq b) => a -> b -> T + -- OK + MkT2 :: forall a. Eq a => forall b. a -> b -> T + -- Rejected, `forall b` is nested + MkT3 :: forall a b. Eq a => Eq b => a -> b -> T + -- Rejected, `Eq b` is nested + MkT4 :: Int -> forall a. a -> T + -- Rejected, `forall a` is nested + MkT5 :: forall a. Int -> Eq a => a -> T + -- Rejected, `Eq a` is nested + MkT6 :: (forall a. a -> T) + -- Rejected, `forall a` is nested due to the surrounding parentheses + MkT7 :: (Eq a => a -> t) + -- Rejected, `Eq a` is nested due to the surrounding parentheses + +For the full details, see the "Formal syntax for GADTs" section of the GHC +User's Guide. GHC enforces that GADT constructors do not have nested `forall`s +or contexts in two parts: + +1. GHC, in the process of splitting apart a GADT's type, + extracts out the leading `forall` and context (if they are provided). To + accomplish this splitting, the renamer uses the + GHC.Hs.Type.splitLHsGADTPrefixTy function, which is careful not to remove + parentheses surrounding the leading `forall` or context (as these + parentheses can be syntactically significant). If the third result returned + by splitLHsGADTPrefixTy contains any `forall`s or contexts, then they must + be nested, so they will be rejected. + + Note that this step applies to both prefix and record GADTs alike, as they + both have syntax which permits `forall`s and contexts. The difference is + where this step happens: + + * For prefix GADTs, this happens in the renamer (in rnConDecl), as we cannot + split until after the type operator fixities have been resolved. + * For record GADTs, this happens in the parser (in mkGadtDecl). +2. If the GADT type is prefix, the renamer (in the ConDeclGADTPrefixPs case of + rnConDecl) will then check for nested `forall`s/contexts in the body of a + prefix GADT type, after it has determined what all of the argument types are. + This step is necessary to catch examples like MkT4 above, where the nested + quantification occurs after a visible argument type. +-} + +-- | The arguments in a Haskell98-style data constructor. +type HsConDeclH98Details pass + = HsConDetails Void (HsScaled pass (LBangType pass)) (XRec pass [LConDeclField pass]) +-- The Void argument to HsConDetails here is a reflection of the fact that +-- type applications are not allowed in data constructor declarations. + +-- | The arguments in a GADT constructor. Unlike Haskell98-style constructors, +-- GADT constructors cannot be declared with infix syntax. As a result, we do +-- not use 'HsConDetails' here, as 'InfixCon' would be an unrepresentable +-- state. (There is a notion of infix GADT constructors for the purposes of +-- derived Show instances—see Note [Infix GADT constructors] in +-- GHC.Tc.TyCl—but that is an orthogonal concern.) +data HsConDeclGADTDetails pass + = PrefixConGADT [HsScaled pass (LBangType pass)] + | RecConGADT (XRec pass [LConDeclField pass]) + +instance Outputable NewOrData where + ppr NewType = text "newtype" + ppr DataType = text "data" + +{- +************************************************************************ +* * + Instance declarations +* * +************************************************************************ + +Note [Type family instance declarations in HsSyn] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +The data type FamEqn represents one equation of a type family instance. +Aside from the pass, it is also parameterised over another field, feqn_rhs. +feqn_rhs is either an HsDataDefn (for data family instances) or an LHsType +(for type family instances). + +Type family instances also include associated type family default equations. +That is because a default for a type family looks like this: + + class C a where + type family F a b :: Type + type F c d = (c,d) -- Default instance + +The default declaration is really just a `type instance` declaration, but one +with particularly simple patterns: they must all be distinct type variables. +That's because we will instantiate it (in an instance declaration for `C`) if +we don't give an explicit instance for `F`. Note that the names of the +variables don't need to match those of the class: it really is like a +free-standing `type instance` declaration. +-} + +----------------- Type synonym family instances ------------- + +-- | Located Type Family Instance Equation +type LTyFamInstEqn pass = XRec pass (TyFamInstEqn pass) + -- ^ May have 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnSemi' + -- when in a list + +-- For details on above see note [Api annotations] in GHC.Parser.Annotation + +-- | Haskell Type Patterns +type HsTyPats pass = [LHsTypeArg pass] + +{- Note [Family instance declaration binders] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +The feqn_pats field of FamEqn (family instance equation) stores the LHS type +(and kind) patterns. Any type (and kind) variables contained +in these type patterns are bound in the feqn_bndrs field. +Note that in particular: + +* The feqn_bndrs *include* any anonymous wildcards. For example + type instance F a _ = a + The feqn_bndrs will be HsOuterImplicit {a, _}. Remember that each separate + wildcard '_' gets its own unique. In this context wildcards behave just like + an ordinary type variable, only anonymous. + +* The feqn_bndrs *include* type variables that are already in scope + + Eg class C s t where + type F t p :: * + instance C w (a,b) where + type F (a,b) x = x->a + The feqn_bndrs of the F decl is HsOuterImplicit {a,b,x}, even though the + F decl is nested inside the 'instance' decl. + + However after the renamer, the uniques will match up: + instance C w7 (a8,b9) where + type F (a8,b9) x10 = x10->a8 + so that we can compare the type pattern in the 'instance' decl and + in the associated 'type' decl + +c.f. Note [TyVar binders for associated decls] +-} + +-- | Type Family Instance Equation +type TyFamInstEqn pass = FamEqn pass (LHsType pass) + -- Here, the @pats@ are type patterns (with kind and type bndrs). + -- See Note [Family instance declaration binders] + +-- | Type family default declarations. +-- A convenient synonym for 'TyFamInstDecl'. +-- See @Note [Type family instance declarations in HsSyn]@. +type TyFamDefltDecl = TyFamInstDecl + +-- | Located type family default declarations. +type LTyFamDefltDecl pass = XRec pass (TyFamDefltDecl pass) + +-- | Located Type Family Instance Declaration +type LTyFamInstDecl pass = XRec pass (TyFamInstDecl pass) + +-- | Type Family Instance Declaration +newtype TyFamInstDecl pass = TyFamInstDecl { tfid_eqn :: TyFamInstEqn pass } + -- ^ + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnType', + -- 'GHC.Parser.Annotation.AnnInstance', + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + +----------------- Data family instances ------------- + +-- | Located Data Family Instance Declaration +type LDataFamInstDecl pass = XRec pass (DataFamInstDecl pass) + +-- | Data Family Instance Declaration +newtype DataFamInstDecl pass + = DataFamInstDecl { dfid_eqn :: FamEqn pass (HsDataDefn pass) } + -- ^ + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnData', + -- 'GHC.Parser.Annotation.AnnNewType','GHC.Parser.Annotation.AnnInstance', + -- 'GHC.Parser.Annotation.AnnDcolon' + -- 'GHC.Parser.Annotation.AnnWhere','GHC.Parser.Annotation.AnnOpen', + -- 'GHC.Parser.Annotation.AnnClose' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + +----------------- Family instances (common types) ------------- + +-- | Family Equation +-- +-- One equation in a type family instance declaration, data family instance +-- declaration, or type family default. +-- See Note [Type family instance declarations in HsSyn] +-- See Note [Family instance declaration binders] +data FamEqn pass rhs + = FamEqn + { feqn_ext :: XCFamEqn pass rhs + , feqn_tycon :: LIdP pass + , feqn_bndrs :: HsOuterFamEqnTyVarBndrs pass -- ^ Optional quantified type vars + , feqn_pats :: HsTyPats pass + , feqn_fixity :: LexicalFixity -- ^ Fixity used in the declaration + , feqn_rhs :: rhs + } + -- ^ + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnEqual' + | XFamEqn !(XXFamEqn pass rhs) + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + +----------------- Class instances ------------- + +-- | Located Class Instance Declaration +type LClsInstDecl pass = XRec pass (ClsInstDecl pass) + +-- | Class Instance Declaration +data ClsInstDecl pass + = ClsInstDecl + { cid_ext :: XCClsInstDecl pass + , cid_poly_ty :: LHsSigType pass -- Context => Class Instance-type + -- Using a polytype means that the renamer conveniently + -- figures out the quantified type variables for us. + , cid_binds :: LHsBinds pass -- Class methods + , cid_sigs :: [LSig pass] -- User-supplied pragmatic info + , cid_tyfam_insts :: [LTyFamInstDecl pass] -- Type family instances + , cid_datafam_insts :: [LDataFamInstDecl pass] -- Data family instances + , cid_overlap_mode :: Maybe (XRec pass OverlapMode) + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen', + -- 'GHC.Parser.Annotation.AnnClose', + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + } + -- ^ + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnInstance', + -- 'GHC.Parser.Annotation.AnnWhere', + -- 'GHC.Parser.Annotation.AnnOpen','GHC.Parser.Annotation.AnnClose', + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | XClsInstDecl !(XXClsInstDecl pass) + +----------------- Instances of all kinds ------------- + +-- | Located Instance Declaration +type LInstDecl pass = XRec pass (InstDecl pass) + +-- | Instance Declaration +data InstDecl pass -- Both class and family instances + = ClsInstD + { cid_d_ext :: XClsInstD pass + , cid_inst :: ClsInstDecl pass } + | DataFamInstD -- data family instance + { dfid_ext :: XDataFamInstD pass + , dfid_inst :: DataFamInstDecl pass } + | TyFamInstD -- type family instance + { tfid_ext :: XTyFamInstD pass + , tfid_inst :: TyFamInstDecl pass } + | XInstDecl !(XXInstDecl pass) + +{- +************************************************************************ +* * +\subsection[DerivDecl]{A stand-alone instance deriving declaration} +* * +************************************************************************ +-} + +-- | Located stand-alone 'deriving instance' declaration +type LDerivDecl pass = XRec pass (DerivDecl pass) + +-- | Stand-alone 'deriving instance' declaration +data DerivDecl pass = DerivDecl + { deriv_ext :: XCDerivDecl pass + , deriv_type :: LHsSigWcType pass + -- ^ The instance type to derive. + -- + -- It uses an 'LHsSigWcType' because the context is allowed to be a + -- single wildcard: + -- + -- > deriving instance _ => Eq (Foo a) + -- + -- Which signifies that the context should be inferred. + + -- See Note [Inferring the instance context] in GHC.Tc.Deriv.Infer. + + , deriv_strategy :: Maybe (LDerivStrategy pass) + , deriv_overlap_mode :: Maybe (XRec pass OverlapMode) + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnDeriving', + -- 'GHC.Parser.Annotation.AnnInstance', 'GHC.Parser.Annotation.AnnStock', + -- 'GHC.Parser.Annotation.AnnAnyClass', 'Api.AnnNewtype', + -- 'GHC.Parser.Annotation.AnnOpen','GHC.Parser.Annotation.AnnClose' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + } + | XDerivDecl !(XXDerivDecl pass) + +{- +************************************************************************ +* * + Deriving strategies +* * +************************************************************************ +-} + +-- | A 'Located' 'DerivStrategy'. +type LDerivStrategy pass = XRec pass (DerivStrategy pass) + +-- | Which technique the user explicitly requested when deriving an instance. +data DerivStrategy pass + -- See Note [Deriving strategies] in GHC.Tc.Deriv + = StockStrategy -- ^ GHC's \"standard\" strategy, which is to implement a + -- custom instance for the data type. This only works + -- for certain types that GHC knows about (e.g., 'Eq', + -- 'Show', 'Functor' when @-XDeriveFunctor@ is enabled, + -- etc.) + | AnyclassStrategy -- ^ @-XDeriveAnyClass@ + | NewtypeStrategy -- ^ @-XGeneralizedNewtypeDeriving@ + | ViaStrategy (XViaStrategy pass) + -- ^ @-XDerivingVia@ + +-- | A short description of a @DerivStrategy'@. +derivStrategyName :: DerivStrategy a -> SDoc +derivStrategyName = text . go + where + go StockStrategy = "stock" + go AnyclassStrategy = "anyclass" + go NewtypeStrategy = "newtype" + go (ViaStrategy {}) = "via" + +{- +************************************************************************ +* * +\subsection[DefaultDecl]{A @default@ declaration} +* * +************************************************************************ + +There can only be one default declaration per module, but it is hard +for the parser to check that; we pass them all through in the abstract +syntax, and that restriction must be checked in the front end. +-} + +-- | Located Default Declaration +type LDefaultDecl pass = XRec pass (DefaultDecl pass) + +-- | Default Declaration +data DefaultDecl pass + = DefaultDecl (XCDefaultDecl pass) [LHsType pass] + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId's : 'GHC.Parser.Annotation.AnnDefault', + -- 'GHC.Parser.Annotation.AnnOpen','GHC.Parser.Annotation.AnnClose' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | XDefaultDecl !(XXDefaultDecl pass) + +{- +************************************************************************ +* * +\subsection{Foreign function interface declaration} +* * +************************************************************************ +-} + +-- foreign declarations are distinguished as to whether they define or use a +-- Haskell name +-- +-- * the Boolean value indicates whether the pre-standard deprecated syntax +-- has been used + +-- | Located Foreign Declaration +type LForeignDecl pass = XRec pass (ForeignDecl pass) + +-- | Foreign Declaration +data ForeignDecl pass + = ForeignImport + { fd_i_ext :: XForeignImport pass -- Post typechecker, rep_ty ~ sig_ty + , fd_name :: LIdP pass -- defines this name + , fd_sig_ty :: LHsSigType pass -- sig_ty + , fd_fi :: ForeignImport } + + | ForeignExport + { fd_e_ext :: XForeignExport pass -- Post typechecker, rep_ty ~ sig_ty + , fd_name :: LIdP pass -- uses this name + , fd_sig_ty :: LHsSigType pass -- sig_ty + , fd_fe :: ForeignExport } + -- ^ + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnForeign', + -- 'GHC.Parser.Annotation.AnnImport','GHC.Parser.Annotation.AnnExport', + -- 'GHC.Parser.Annotation.AnnDcolon' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | XForeignDecl !(XXForeignDecl pass) + +{- + In both ForeignImport and ForeignExport: + sig_ty is the type given in the Haskell code + rep_ty is the representation for this type, i.e. with newtypes + coerced away and type functions evaluated. + Thus if the declaration is valid, then rep_ty will only use types + such as Int and IO that we know how to make foreign calls with. +-} + +-- Specification Of an imported external entity in dependence on the calling +-- convention +-- +data ForeignImport = -- import of a C entity + -- + -- * the two strings specifying a header file or library + -- may be empty, which indicates the absence of a + -- header or object specification (both are not used + -- in the case of `CWrapper' and when `CFunction' + -- has a dynamic target) + -- + -- * the calling convention is irrelevant for code + -- generation in the case of `CLabel', but is needed + -- for pretty printing + -- + -- * `Safety' is irrelevant for `CLabel' and `CWrapper' + -- + CImport (Located CCallConv) -- ccall or stdcall + (Located Safety) -- interruptible, safe or unsafe + (Maybe Header) -- name of C header + CImportSpec -- details of the C entity + (Located SourceText) -- original source text for + -- the C entity + deriving Data + +-- details of an external C entity +-- +data CImportSpec = CLabel CLabelString -- import address of a C label + | CFunction CCallTarget -- static or dynamic function + | CWrapper -- wrapper to expose closures + -- (former f.e.d.) + deriving Data + +-- specification of an externally exported entity in dependence on the calling +-- convention +-- +data ForeignExport = CExport (Located CExportSpec) -- contains the calling + -- convention + (Located SourceText) -- original source text for + -- the C entity + deriving Data + +-- pretty printing of foreign declarations +-- + +instance Outputable ForeignImport where + ppr (CImport cconv safety mHeader spec (L _ srcText)) = + ppr cconv <+> ppr safety + <+> pprWithSourceText srcText (pprCEntity spec "") + where + pp_hdr = case mHeader of + Nothing -> empty + Just (Header _ header) -> ftext header + + pprCEntity (CLabel lbl) _ = + doubleQuotes $ text "static" <+> pp_hdr <+> char '&' <> ppr lbl + pprCEntity (CFunction (StaticTarget st _lbl _ isFun)) src = + if dqNeeded then doubleQuotes ce else empty + where + dqNeeded = (take 6 src == "static") + || isJust mHeader + || not isFun + || st /= NoSourceText + ce = + -- We may need to drop leading spaces first + (if take 6 src == "static" then text "static" else empty) + <+> pp_hdr + <+> (if isFun then empty else text "value") + <+> (pprWithSourceText st empty) + pprCEntity (CFunction DynamicTarget) _ = + doubleQuotes $ text "dynamic" + pprCEntity CWrapper _ = doubleQuotes $ text "wrapper" + +instance Outputable ForeignExport where + ppr (CExport (L _ (CExportStatic _ lbl cconv)) _) = + ppr cconv <+> char '"' <> ppr lbl <> char '"' + +{- +************************************************************************ +* * +\subsection{Rewrite rules} +* * +************************************************************************ +-} + +-- | Located Rule Declarations +type LRuleDecls pass = XRec pass (RuleDecls pass) + + -- Note [Pragma source text] in GHC.Types.SourceText +-- | Rule Declarations +data RuleDecls pass = HsRules { rds_ext :: XCRuleDecls pass + , rds_src :: SourceText + , rds_rules :: [LRuleDecl pass] } + | XRuleDecls !(XXRuleDecls pass) + +-- | Located Rule Declaration +type LRuleDecl pass = XRec pass (RuleDecl pass) + +-- | Rule Declaration +data RuleDecl pass + = HsRule -- Source rule + { rd_ext :: XHsRule pass + -- ^ After renamer, free-vars from the LHS and RHS + , rd_name :: XRec pass (SourceText,RuleName) + -- ^ Note [Pragma source text] in "GHC.Types.Basic" + , rd_act :: Activation + , rd_tyvs :: Maybe [LHsTyVarBndr () (NoGhcTc pass)] + -- ^ Forall'd type vars + , rd_tmvs :: [LRuleBndr pass] + -- ^ Forall'd term vars, before typechecking; after typechecking + -- this includes all forall'd vars + , rd_lhs :: XRec pass (HsExpr pass) + , rd_rhs :: XRec pass (HsExpr pass) + } + -- ^ + -- - 'GHC.Parser.Annotation.AnnKeywordId' : + -- 'GHC.Parser.Annotation.AnnOpen','GHC.Parser.Annotation.AnnTilde', + -- 'GHC.Parser.Annotation.AnnVal', + -- 'GHC.Parser.Annotation.AnnClose', + -- 'GHC.Parser.Annotation.AnnForall','GHC.Parser.Annotation.AnnDot', + -- 'GHC.Parser.Annotation.AnnEqual', + | XRuleDecl !(XXRuleDecl pass) + +data HsRuleRn = HsRuleRn NameSet NameSet -- Free-vars from the LHS and RHS + deriving Data + +-- | Located Rule Binder +type LRuleBndr pass = XRec pass (RuleBndr pass) + +-- | Rule Binder +data RuleBndr pass + = RuleBndr (XCRuleBndr pass) (LIdP pass) + | RuleBndrSig (XRuleBndrSig pass) (LIdP pass) (HsPatSigType pass) + | XRuleBndr !(XXRuleBndr pass) + -- ^ + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen', + -- 'GHC.Parser.Annotation.AnnDcolon','GHC.Parser.Annotation.AnnClose' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + +collectRuleBndrSigTys :: [RuleBndr pass] -> [HsPatSigType pass] +collectRuleBndrSigTys bndrs = [ty | RuleBndrSig _ _ ty <- bndrs] + +pprFullRuleName :: Located (SourceText, RuleName) -> SDoc +pprFullRuleName (L _ (st, n)) = pprWithSourceText st (doubleQuotes $ ftext n) + +{- +************************************************************************ +* * +\subsection[DocDecl]{Document comments} +* * +************************************************************************ +-} + +-- | Located Documentation comment Declaration +type LDocDecl = Located (DocDecl) + +-- | Documentation comment Declaration +data DocDecl + = DocCommentNext HsDocString + | DocCommentPrev HsDocString + | DocCommentNamed String HsDocString + | DocGroup Int HsDocString + deriving Data + +-- Okay, I need to reconstruct the document comments, but for now: +instance Outputable DocDecl where + ppr _ = text "<document comment>" + +docDeclDoc :: DocDecl -> HsDocString +docDeclDoc (DocCommentNext d) = d +docDeclDoc (DocCommentPrev d) = d +docDeclDoc (DocCommentNamed _ d) = d +docDeclDoc (DocGroup _ d) = d + +{- +************************************************************************ +* * +\subsection[DeprecDecl]{Deprecations} +* * +************************************************************************ + +We use exported entities for things to deprecate. +-} + +-- | Located Warning Declarations +type LWarnDecls pass = XRec pass (WarnDecls pass) + + -- Note [Pragma source text] in GHC.Types.SourceText +-- | Warning pragma Declarations +data WarnDecls pass = Warnings { wd_ext :: XWarnings pass + , wd_src :: SourceText + , wd_warnings :: [LWarnDecl pass] + } + | XWarnDecls !(XXWarnDecls pass) + +-- | Located Warning pragma Declaration +type LWarnDecl pass = XRec pass (WarnDecl pass) + +-- | Warning pragma Declaration +data WarnDecl pass = Warning (XWarning pass) [LIdP pass] WarningTxt + | XWarnDecl !(XXWarnDecl pass) + +{- +************************************************************************ +* * +\subsection[AnnDecl]{Annotations} +* * +************************************************************************ +-} + +-- | Located Annotation Declaration +type LAnnDecl pass = XRec pass (AnnDecl pass) + +-- | Annotation Declaration +data AnnDecl pass = HsAnnotation + (XHsAnnotation pass) + SourceText -- Note [Pragma source text] in GHC.Types.SourceText + (AnnProvenance (IdP pass)) (XRec pass (HsExpr pass)) + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen', + -- 'GHC.Parser.Annotation.AnnType' + -- 'GHC.Parser.Annotation.AnnModule' + -- 'GHC.Parser.Annotation.AnnClose' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | XAnnDecl !(XXAnnDecl pass) + +-- | Annotation Provenance +data AnnProvenance name = ValueAnnProvenance (Located name) + | TypeAnnProvenance (Located name) + | ModuleAnnProvenance +deriving instance Functor AnnProvenance +deriving instance Foldable AnnProvenance +deriving instance Traversable AnnProvenance +deriving instance (Data pass) => Data (AnnProvenance pass) + +annProvenanceName_maybe :: AnnProvenance name -> Maybe name +annProvenanceName_maybe (ValueAnnProvenance (L _ name)) = Just name +annProvenanceName_maybe (TypeAnnProvenance (L _ name)) = Just name +annProvenanceName_maybe ModuleAnnProvenance = Nothing + +{- +************************************************************************ +* * +\subsection[RoleAnnot]{Role annotations} +* * +************************************************************************ +-} + +-- | Located Role Annotation Declaration +type LRoleAnnotDecl pass = XRec pass (RoleAnnotDecl pass) + +-- See #8185 for more info about why role annotations are +-- top-level declarations +-- | Role Annotation Declaration +data RoleAnnotDecl pass + = RoleAnnotDecl (XCRoleAnnotDecl pass) + (LIdP pass) -- type constructor + [XRec pass (Maybe Role)] -- optional annotations + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnType', + -- 'GHC.Parser.Annotation.AnnRole' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | XRoleAnnotDecl !(XXRoleAnnotDecl pass) diff --git a/compiler/Language/Haskell/Syntax/Expr.hs b/compiler/Language/Haskell/Syntax/Expr.hs new file mode 100644 index 0000000000..ecc7c9f828 --- /dev/null +++ b/compiler/Language/Haskell/Syntax/Expr.hs @@ -0,0 +1,1776 @@ +{-# LANGUAGE CPP #-} +{-# LANGUAGE ConstraintKinds #-} +{-# LANGUAGE DataKinds #-} +{-# LANGUAGE DeriveDataTypeable #-} +{-# LANGUAGE ExistentialQuantification #-} +{-# LANGUAGE FlexibleContexts #-} +{-# LANGUAGE FlexibleInstances #-} +{-# LANGUAGE LambdaCase #-} +{-# LANGUAGE ScopedTypeVariables #-} +{-# LANGUAGE StandaloneDeriving #-} +{-# LANGUAGE TypeApplications #-} +{-# LANGUAGE TypeFamilyDependencies #-} +{-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow] + -- in module Language.Haskell.Syntax.Extension + +{-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-} + +{- +(c) The University of Glasgow 2006 +(c) The GRASP/AQUA Project, Glasgow University, 1992-1998 +-} + +-- See Note [Language.Haskell.Syntax.* Hierarchy] for why not GHC.Hs.* + +-- | Abstract Haskell syntax for expressions. +module Language.Haskell.Syntax.Expr where + +#include "HsVersions.h" + +-- friends: +import GHC.Prelude + +import Language.Haskell.Syntax.Decls +import Language.Haskell.Syntax.Pat +import Language.Haskell.Syntax.Lit +import Language.Haskell.Syntax.Extension +import Language.Haskell.Syntax.Type +import Language.Haskell.Syntax.Binds + +-- others: +import GHC.Tc.Types.Evidence +import GHC.Core +import GHC.Types.Name +import GHC.Types.Basic +import GHC.Types.Fixity +import GHC.Types.SourceText +import GHC.Types.SrcLoc +import GHC.Core.ConLike +import GHC.Unit.Module (ModuleName) +import GHC.Utils.Outputable +import GHC.Utils.Panic +import GHC.Data.FastString +import GHC.Core.Type + +-- libraries: +import Data.Data hiding (Fixity(..)) +import qualified Data.Data as Data (Fixity(..)) + +import GHCi.RemoteTypes ( ForeignRef ) +import qualified Language.Haskell.TH as TH (Q) + +{- +************************************************************************ +* * +\subsection{Expressions proper} +* * +************************************************************************ +-} + +-- * Expressions proper + +-- | Located Haskell Expression +type LHsExpr p = XRec p (HsExpr p) + -- ^ May have 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnComma' when + -- in a list + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + +------------------------- +{- Note [NoSyntaxExpr] +~~~~~~~~~~~~~~~~~~~~~~ +Syntax expressions can be missing (NoSyntaxExprRn or NoSyntaxExprTc) +for several reasons: + + 1. As described in Note [Rebindable if] + + 2. In order to suppress "not in scope: xyz" messages when a bit of + rebindable syntax does not apply. For example, when using an irrefutable + pattern in a BindStmt, we don't need a `fail` operator. + + 3. Rebindable syntax might just not make sense. For example, a BodyStmt + contains the syntax for `guard`, but that's used only in monad comprehensions. + If we had more of a whiz-bang type system, we might be able to rule this + case out statically. +-} + +-- | Syntax Expression +-- +-- SyntaxExpr is represents the function used in interpreting rebindable +-- syntax. In the parser, we have no information to supply; in the renamer, +-- we have the name of the function (but see +-- Note [Monad fail : Rebindable syntax, overloaded strings] for a wrinkle) +-- and in the type-checker we have a more elaborate structure 'SyntaxExprTc'. +-- +-- In some contexts, rebindable syntax is not implemented, and so we have +-- constructors to represent that possibility in both the renamer and +-- typechecker instantiations. +-- +-- E.g. @(>>=)@ is filled in before the renamer by the appropriate 'Name' for +-- @(>>=)@, and then instantiated by the type checker with its type args +-- etc +type family SyntaxExpr p + +-- | Command Syntax Table (for Arrow syntax) +type CmdSyntaxTable p = [(Name, HsExpr p)] +-- See Note [CmdSyntaxTable] + +{- +Note [CmdSyntaxTable] +~~~~~~~~~~~~~~~~~~~~~ +Used only for arrow-syntax stuff (HsCmdTop), the CmdSyntaxTable keeps +track of the methods needed for a Cmd. + +* Before the renamer, this list is an empty list + +* After the renamer, it takes the form @[(std_name, HsVar actual_name)]@ + For example, for the 'arr' method + * normal case: (GHC.Control.Arrow.arr, HsVar GHC.Control.Arrow.arr) + * with rebindable syntax: (GHC.Control.Arrow.arr, arr_22) + where @arr_22@ is whatever 'arr' is in scope + +* After the type checker, it takes the form [(std_name, <expression>)] + where <expression> is the evidence for the method. This evidence is + instantiated with the class, but is still polymorphic in everything + else. For example, in the case of 'arr', the evidence has type + forall b c. (b->c) -> a b c + where 'a' is the ambient type of the arrow. This polymorphism is + important because the desugarer uses the same evidence at multiple + different types. + +This is Less Cool than what we normally do for rebindable syntax, which is to +make fully-instantiated piece of evidence at every use site. The Cmd way +is Less Cool because + * The renamer has to predict which methods are needed. + See the tedious GHC.Rename.Expr.methodNamesCmd. + + * The desugarer has to know the polymorphic type of the instantiated + method. This is checked by Inst.tcSyntaxName, but is less flexible + than the rest of rebindable syntax, where the type is less + pre-ordained. (And this flexibility is useful; for example we can + typecheck do-notation with (>>=) :: m1 a -> (a -> m2 b) -> m2 b.) +-} + +-- | A Haskell expression. +data HsExpr p + = HsVar (XVar p) + (LIdP p) -- ^ Variable + -- See Note [Located RdrNames] + + | HsUnboundVar (XUnboundVar p) + OccName -- ^ Unbound variable; also used for "holes" + -- (_ or _x). + -- Turned from HsVar to HsUnboundVar by the + -- renamer, when it finds an out-of-scope + -- variable or hole. + -- The (XUnboundVar p) field becomes an HoleExprRef + -- after typechecking; this is where the + -- erroring expression will be written after + -- solving. See Note [Holes] in GHC.Tc.Types.Constraint. + + | HsConLikeOut (XConLikeOut p) + ConLike -- ^ After typechecker only; must be different + -- HsVar for pretty printing + + | HsRecFld (XRecFld p) + (AmbiguousFieldOcc p) -- ^ Variable pointing to record selector + -- The parser produces HsVars + -- The renamer renames record-field selectors to HsRecFld + -- The typechecker preserves HsRecFld + + | HsOverLabel (XOverLabel p) + (Maybe (IdP p)) FastString + -- ^ Overloaded label (Note [Overloaded labels] in GHC.OverloadedLabels) + -- @Just id@ means @RebindableSyntax@ is in use, and gives the id of the + -- in-scope 'fromLabel'. + -- NB: Not in use after typechecking + + | HsIPVar (XIPVar p) + HsIPName -- ^ Implicit parameter (not in use after typechecking) + | HsOverLit (XOverLitE p) + (HsOverLit p) -- ^ Overloaded literals + + | HsLit (XLitE p) + (HsLit p) -- ^ Simple (non-overloaded) literals + + | HsLam (XLam p) + (MatchGroup p (LHsExpr p)) + -- ^ Lambda abstraction. Currently always a single match + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnLam', + -- 'GHC.Parser.Annotation.AnnRarrow', + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | HsLamCase (XLamCase p) (MatchGroup p (LHsExpr p)) -- ^ Lambda-case + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnLam', + -- 'GHC.Parser.Annotation.AnnCase','GHC.Parser.Annotation.AnnOpen', + -- 'GHC.Parser.Annotation.AnnClose' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | HsApp (XApp p) (LHsExpr p) (LHsExpr p) -- ^ Application + + | HsAppType (XAppTypeE p) -- After typechecking: the type argument + (LHsExpr p) + (LHsWcType (NoGhcTc p)) -- ^ Visible type application + -- + -- Explicit type argument; e.g f @Int x y + -- NB: Has wildcards, but no implicit quantification + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnAt', + + -- | Operator applications: + -- NB Bracketed ops such as (+) come out as Vars. + + -- NB We need an expr for the operator in an OpApp/Section since + -- the typechecker may need to apply the operator to a few types. + + | OpApp (XOpApp p) + (LHsExpr p) -- left operand + (LHsExpr p) -- operator + (LHsExpr p) -- right operand + + -- | Negation operator. Contains the negated expression and the name + -- of 'negate' + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnMinus' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | NegApp (XNegApp p) + (LHsExpr p) + (SyntaxExpr p) + + -- | - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @'('@, + -- 'GHC.Parser.Annotation.AnnClose' @')'@ + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | HsPar (XPar p) + (LHsExpr p) -- ^ Parenthesised expr; see Note [Parens in HsSyn] + + | SectionL (XSectionL p) + (LHsExpr p) -- operand; see Note [Sections in HsSyn] + (LHsExpr p) -- operator + | SectionR (XSectionR p) + (LHsExpr p) -- operator; see Note [Sections in HsSyn] + (LHsExpr p) -- operand + + -- | Used for explicit tuples and sections thereof + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen', + -- 'GHC.Parser.Annotation.AnnClose' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + -- Note [ExplicitTuple] + | ExplicitTuple + (XExplicitTuple p) + [LHsTupArg p] + Boxity + + -- | Used for unboxed sum types + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @'(#'@, + -- 'GHC.Parser.Annotation.AnnVbar', 'GHC.Parser.Annotation.AnnClose' @'#)'@, + -- + -- There will be multiple 'GHC.Parser.Annotation.AnnVbar', (1 - alternative) before + -- the expression, (arity - alternative) after it + | ExplicitSum + (XExplicitSum p) + ConTag -- Alternative (one-based) + Arity -- Sum arity + (LHsExpr p) + + -- | - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnCase', + -- 'GHC.Parser.Annotation.AnnOf','GHC.Parser.Annotation.AnnOpen' @'{'@, + -- 'GHC.Parser.Annotation.AnnClose' @'}'@ + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | HsCase (XCase p) + (LHsExpr p) + (MatchGroup p (LHsExpr p)) + + -- | - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnIf', + -- 'GHC.Parser.Annotation.AnnSemi', + -- 'GHC.Parser.Annotation.AnnThen','GHC.Parser.Annotation.AnnSemi', + -- 'GHC.Parser.Annotation.AnnElse', + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | HsIf (XIf p) -- GhcPs: this is a Bool; False <=> do not use + -- rebindable syntax + (LHsExpr p) -- predicate + (LHsExpr p) -- then part + (LHsExpr p) -- else part + + -- | Multi-way if + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnIf' + -- 'GHC.Parser.Annotation.AnnOpen','GHC.Parser.Annotation.AnnClose', + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | HsMultiIf (XMultiIf p) [LGRHS p (LHsExpr p)] + + -- | let(rec) + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnLet', + -- 'GHC.Parser.Annotation.AnnOpen' @'{'@, + -- 'GHC.Parser.Annotation.AnnClose' @'}'@,'GHC.Parser.Annotation.AnnIn' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | HsLet (XLet p) + (LHsLocalBinds p) + (LHsExpr p) + + -- | - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnDo', + -- 'GHC.Parser.Annotation.AnnOpen', 'GHC.Parser.Annotation.AnnSemi', + -- 'GHC.Parser.Annotation.AnnVbar', + -- 'GHC.Parser.Annotation.AnnClose' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | HsDo (XDo p) -- Type of the whole expression + (HsStmtContext (HsDoRn p)) + -- The parameterisation of the above is unimportant + -- because in this context we never use + -- the PatGuard or ParStmt variant + (XRec p [ExprLStmt p]) -- "do":one or more stmts + + -- | Syntactic list: [a,b,c,...] + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @'['@, + -- 'GHC.Parser.Annotation.AnnClose' @']'@ + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + -- See Note [Empty lists] + | ExplicitList + (XExplicitList p) -- Gives type of components of list + (Maybe (SyntaxExpr p)) + -- For OverloadedLists, the fromListN witness + [LHsExpr p] + + -- | Record construction + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @'{'@, + -- 'GHC.Parser.Annotation.AnnDotdot','GHC.Parser.Annotation.AnnClose' @'}'@ + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | RecordCon + { rcon_ext :: XRecordCon p + , rcon_con_name :: LIdP p -- The constructor name; + -- not used after type checking + , rcon_flds :: HsRecordBinds p } -- The fields + + -- | Record update + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @'{'@, + -- 'GHC.Parser.Annotation.AnnDotdot','GHC.Parser.Annotation.AnnClose' @'}'@ + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | RecordUpd + { rupd_ext :: XRecordUpd p + , rupd_expr :: LHsExpr p + , rupd_flds :: [LHsRecUpdField p] + } + -- For a type family, the arg types are of the *instance* tycon, + -- not the family tycon + + -- | Expression with an explicit type signature. @e :: type@ + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnDcolon' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | ExprWithTySig + (XExprWithTySig p) + + (LHsExpr p) + (LHsSigWcType (NoGhcTc p)) + + -- | Arithmetic sequence + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @'['@, + -- 'GHC.Parser.Annotation.AnnComma','GHC.Parser.Annotation.AnnDotdot', + -- 'GHC.Parser.Annotation.AnnClose' @']'@ + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | ArithSeq + (XArithSeq p) + (Maybe (SyntaxExpr p)) + -- For OverloadedLists, the fromList witness + (ArithSeqInfo p) + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + ----------------------------------------------------------- + -- MetaHaskell Extensions + + -- | - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen', + -- 'GHC.Parser.Annotation.AnnOpenE','GHC.Parser.Annotation.AnnOpenEQ', + -- 'GHC.Parser.Annotation.AnnClose','GHC.Parser.Annotation.AnnCloseQ' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | HsBracket (XBracket p) (HsBracket p) + + -- See Note [Pending Splices] + | HsRnBracketOut + (XRnBracketOut p) + (HsBracket (HsBracketRn p)) -- Output of the renamer is the *original* renamed + -- expression, plus + [PendingRnSplice' p] -- _renamed_ splices to be type checked + + | HsTcBracketOut + (XTcBracketOut p) + (Maybe QuoteWrapper) -- The wrapper to apply type and dictionary argument + -- to the quote. + (HsBracket (HsBracketRn p)) -- Output of the type checker is the *original* + -- renamed expression, plus + [PendingTcSplice' p] -- _typechecked_ splices to be + -- pasted back in by the desugarer + + -- | - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen', + -- 'GHC.Parser.Annotation.AnnClose' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | HsSpliceE (XSpliceE p) (HsSplice p) + + ----------------------------------------------------------- + -- Arrow notation extension + + -- | @proc@ notation for Arrows + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnProc', + -- 'GHC.Parser.Annotation.AnnRarrow' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | HsProc (XProc p) + (LPat p) -- arrow abstraction, proc + (LHsCmdTop p) -- body of the abstraction + -- always has an empty stack + + --------------------------------------- + -- static pointers extension + -- | - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnStatic', + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | HsStatic (XStatic p) -- Free variables of the body + (LHsExpr p) -- Body + + --------------------------------------- + -- Haskell program coverage (Hpc) Support + + | HsTick + (XTick p) + (Tickish (IdP p)) + (LHsExpr p) -- sub-expression + + | HsBinTick + (XBinTick p) + Int -- module-local tick number for True + Int -- module-local tick number for False + (LHsExpr p) -- sub-expression + + --------------------------------------- + -- Expressions annotated with pragmas, written as {-# ... #-} + | HsPragE (XPragE p) (HsPragE p) (LHsExpr p) + + | XExpr !(XXExpr p) + -- Note [Trees that Grow] extension constructor for the + -- general idea, and Note [Rebindable syntax and HsExpansion] + -- for an example of how we use it. + +-- | The AST used to hard-refer to GhcPass, which was a layer violation. For now, +-- we paper it over with this new extension point. +type family HsDoRn p +type family HsBracketRn p +type family PendingRnSplice' p +type family PendingTcSplice' p + +-- --------------------------------------------------------------------- + +{- +Note [Rebindable syntax and HsExpansion] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +We implement rebindable syntax (RS) support by performing a desugaring +in the renamer. We transform GhcPs expressions affected by RS into the +appropriate desugared form, but **annotated with the original expression**. + +Let us consider a piece of code like: + + {-# LANGUAGE RebindableSyntax #-} + ifThenElse :: Char -> () -> () -> () + ifThenElse _ _ _ = () + x = if 'a' then () else True + +The parsed AST for the RHS of x would look something like (slightly simplified): + + L locif (HsIf (L loca 'a') (L loctrue ()) (L locfalse True)) + +Upon seeing such an AST with RS on, we could transform it into a +mere function call, as per the RS rules, equivalent to the +following function application: + + ifThenElse 'a' () True + +which doesn't typecheck. But GHC would report an error about +not being able to match the third argument's type (Bool) with the +expected type: (), in the expression _as desugared_, i.e in +the aforementioned function application. But the user never +wrote a function application! This would be pretty bad. + +To remedy this, instead of transforming the original HsIf +node into mere applications of 'ifThenElse', we keep the +original 'if' expression around too, using the TTG +XExpr extension point to allow GHC to construct an +'HsExpansion' value that will keep track of the original +expression in its first field, and the desugared one in the +second field. The resulting renamed AST would look like: + + L locif (XExpr + (HsExpanded + (HsIf (L loca 'a') + (L loctrue ()) + (L locfalse True) + ) + (App (L generatedSrcSpan + (App (L generatedSrcSpan + (App (L generatedSrcSpan (Var ifThenElse)) + (L loca 'a') + ) + ) + (L loctrue ()) + ) + ) + (L locfalse True) + ) + ) + ) + +When comes the time to typecheck the program, we end up calling +tcMonoExpr on the AST above. If this expression gives rise to +a type error, then it will appear in a context line and GHC +will pretty-print it using the 'Outputable (HsExpansion a b)' +instance defined below, which *only prints the original +expression*. This is the gist of the idea, but is not quite +enough to recover the error messages that we had with the +SyntaxExpr-based, typechecking/desugaring-to-core time +implementation of rebindable syntax. The key idea is to decorate +some elements of the desugared expression so as to be able to +give them a special treatment when typechecking the desugared +expression, to print a different context line or skip one +altogether. + +Whenever we 'setSrcSpan' a 'generatedSrcSpan', we update a field in +TcLclEnv called 'tcl_in_gen_code', setting it to True, which indicates that we +entered generated code, i.e code fabricated by the compiler when rebinding some +syntax. If someone tries to push some error context line while that field is set +to True, the pushing won't actually happen and the context line is just dropped. +Once we 'setSrcSpan' a real span (for an expression that was in the original +source code), we set 'tcl_in_gen_code' back to False, indicating that we +"emerged from the generated code tunnel", and that the expressions we will be +processing are relevant to report in context lines again. + +You might wonder why we store a RealSrcSpan in addition to a Bool in +the TcLclEnv: could we not store a Maybe RealSrcSpan? The problem is +that we still generate constraints when processing generated code, +and a CtLoc must contain a RealSrcSpan -- otherwise, error messages +might appear without source locations. So we keep the RealSrcSpan of +the last location spotted that wasn't generated; it's as good as +we're going to get in generated code. Once we get to sub-trees that +are not generated, then we update the RealSrcSpan appropriately, and +set the tcl_in_gen_code Bool to False. + +--- + +A general recipe to follow this approach for new constructs could go as follows: + +- Remove any GhcRn-time SyntaxExpr extensions to the relevant constructor for your + construct, in HsExpr or related syntax data types. +- At renaming-time: + - take your original node of interest (HsIf above) + - rename its subexpressions (condition, true branch, false branch above) + - construct the suitable "rebound"-and-renamed result (ifThenElse call + above), where the 'SrcSpan' attached to any _fabricated node_ (the + HsVar/HsApp nodes, above) is set to 'generatedSrcSpan' + - take both the original node and that rebound-and-renamed result and wrap + them in an XExpr: XExpr (HsExpanded <original node> <desugared>) + - At typechecking-time: + - remove any logic that was previously dealing with your rebindable + construct, typically involving [tc]SyntaxOp, SyntaxExpr and friends. + - the XExpr (HsExpanded ... ...) case in tcExpr already makes sure that we + typecheck the desugared expression while reporting the original one in + errors + +-} + +-- See Note [Rebindable syntax and HsExpansion] just above. +data HsExpansion a b + = HsExpanded a b + deriving Data + +-- | Build a "wrapped" 'HsExpansion' out of an extension constructor, +-- and the two components of the expansion: original and desugared +-- expressions. +-- +-- See Note [Rebindable Syntax and HsExpansion] above for more details. +mkExpanded + :: (HsExpansion a b -> b) -- ^ XExpr, XCmd, ... + -> a -- ^ source expression ('GhcPs') + -> b -- ^ "desugared" expression + -- ('GhcRn') + -> b -- ^ suitably wrapped + -- 'HsExpansion' +mkExpanded xwrap a b = xwrap (HsExpanded a b) + +-- | Just print the original expression (the @a@). +instance (Outputable a, Outputable b) => Outputable (HsExpansion a b) where + ppr (HsExpanded a b) = ifPprDebug (vcat [ppr a, ppr b]) (ppr a) + +-- --------------------------------------------------------------------- + +-- | A pragma, written as {-# ... #-}, that may appear within an expression. +data HsPragE p + = HsPragSCC (XSCC p) + SourceText -- Note [Pragma source text] in GHC.Types.SourceText + StringLiteral -- "set cost centre" SCC pragma + + -- | - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen', + -- 'GHC.Parser.Annotation.AnnOpen' @'{-\# GENERATED'@, + -- 'GHC.Parser.Annotation.AnnVal','GHC.Parser.Annotation.AnnVal', + -- 'GHC.Parser.Annotation.AnnColon','GHC.Parser.Annotation.AnnVal', + -- 'GHC.Parser.Annotation.AnnMinus', + -- 'GHC.Parser.Annotation.AnnVal','GHC.Parser.Annotation.AnnColon', + -- 'GHC.Parser.Annotation.AnnVal', + -- 'GHC.Parser.Annotation.AnnClose' @'\#-}'@ + + | XHsPragE !(XXPragE p) + +-- | Located Haskell Tuple Argument +-- +-- 'HsTupArg' is used for tuple sections +-- @(,a,)@ is represented by +-- @ExplicitTuple [Missing ty1, Present a, Missing ty3]@ +-- Which in turn stands for @(\x:ty1 \y:ty2. (x,a,y))@ +type LHsTupArg id = XRec id (HsTupArg id) +-- | - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnComma' + +-- For details on above see note [Api annotations] in GHC.Parser.Annotation + +-- | Haskell Tuple Argument +data HsTupArg id + = Present (XPresent id) (LHsExpr id) -- ^ The argument + | Missing (XMissing id) -- ^ The argument is missing, but this is its type + | XTupArg !(XXTupArg id) -- ^ Note [Trees that Grow] extension point + +{- +Note [Parens in HsSyn] +~~~~~~~~~~~~~~~~~~~~~~ +HsPar (and ParPat in patterns, HsParTy in types) is used as follows + + * HsPar is required; the pretty printer does not add parens. + + * HsPars are respected when rearranging operator fixities. + So a * (b + c) means what it says (where the parens are an HsPar) + + * For ParPat and HsParTy the pretty printer does add parens but this should be + a no-op for ParsedSource, based on the pretty printer round trip feature + introduced in + https://phabricator.haskell.org/rGHC499e43824bda967546ebf95ee33ec1f84a114a7c + + * ParPat and HsParTy are pretty printed as '( .. )' regardless of whether or + not they are strictly necessary. This should be addressed when #13238 is + completed, to be treated the same as HsPar. + + +Note [Sections in HsSyn] +~~~~~~~~~~~~~~~~~~~~~~~~ +Sections should always appear wrapped in an HsPar, thus + HsPar (SectionR ...) +The parser parses sections in a wider variety of situations +(See Note [Parsing sections]), but the renamer checks for those +parens. This invariant makes pretty-printing easier; we don't need +a special case for adding the parens round sections. + +Note [Rebindable if] +~~~~~~~~~~~~~~~~~~~~ +The rebindable syntax for 'if' is a bit special, because when +rebindable syntax is *off* we do not want to treat + (if c then t else e) +as if it was an application (ifThenElse c t e). Why not? +Because we allow an 'if' to return *unboxed* results, thus + if blah then 3# else 4# +whereas that would not be possible using a all to a polymorphic function +(because you can't call a polymorphic function at an unboxed type). + +So we use NoSyntaxExpr to mean "use the old built-in typing rule". + +A further complication is that, in the `deriving` code, we never want +to use rebindable syntax. So, even in GhcPs, we want to denote whether +to use rebindable syntax or not. This is done via the type instance +for XIf GhcPs. + +Note [Record Update HsWrapper] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +There is a wrapper in RecordUpd which is used for the *required* +constraints for pattern synonyms. This wrapper is created in the +typechecking and is then directly used in the desugaring without +modification. + +For example, if we have the record pattern synonym P, + pattern P :: (Show a) => a -> Maybe a + pattern P{x} = Just x + + foo = (Just True) { x = False } +then `foo` desugars to something like + foo = case Just True of + P x -> P False +hence we need to provide the correct dictionaries to P's matcher on +the RHS so that we can build the expression. + +Note [Located RdrNames] +~~~~~~~~~~~~~~~~~~~~~~~ +A number of syntax elements have seemingly redundant locations attached to them. +This is deliberate, to allow transformations making use of the API Annotations +to easily correlate a Located Name in the RenamedSource with a Located RdrName +in the ParsedSource. + +There are unfortunately enough differences between the ParsedSource and the +RenamedSource that the API Annotations cannot be used directly with +RenamedSource, so this allows a simple mapping to be used based on the location. + +Note [ExplicitTuple] +~~~~~~~~~~~~~~~~~~~~ +An ExplicitTuple is never just a data constructor like (,,,). +That is, the `[LHsTupArg p]` argument of `ExplicitTuple` has at least +one `Present` member (and is thus never empty). + +A tuple data constructor like () or (,,,) is parsed as an `HsVar`, not an +`ExplicitTuple`, and stays that way. This is important for two reasons: + + 1. We don't need -XTupleSections for (,,,) + 2. The type variables in (,,,) can be instantiated with visible type application. + That is, + + (,,) :: forall a b c. a -> b -> c -> (a,b,c) + (True,,) :: forall {b} {c}. b -> c -> (Bool,b,c) + + Note that the tuple section has *inferred* arguments, while the data + constructor has *specified* ones. + (See Note [Required, Specified, and Inferred for types] in GHC.Tc.TyCl + for background.) + +Sadly, the grammar for this is actually ambiguous, and it's only thanks to the +preference of a shift in a shift/reduce conflict that the parser works as this +Note details. Search for a reference to this Note in GHC.Parser for further +explanation. + +Note [Empty lists] +~~~~~~~~~~~~~~~~~~ +An empty list could be considered either a data constructor (stored with +HsVar) or an ExplicitList. This Note describes how empty lists flow through the +various phases and why. + +Parsing +------- +An empty list is parsed by the sysdcon nonterminal. It thus comes to life via +HsVar nilDataCon (defined in GHC.Builtin.Types). A freshly-parsed (HsExpr GhcPs) empty list +is never a ExplicitList. + +Renaming +-------- +If -XOverloadedLists is enabled, we must type-check the empty list as if it +were a call to fromListN. (This is true regardless of the setting of +-XRebindableSyntax.) This is very easy if the empty list is an ExplicitList, +but an annoying special case if it's an HsVar. So the renamer changes a +HsVar nilDataCon to an ExplicitList [], but only if -XOverloadedLists is on. +(Why not always? Read on, dear friend.) This happens in the HsVar case of rnExpr. + +Type-checking +------------- +We want to accept an expression like [] @Int. To do this, we must infer that +[] :: forall a. [a]. This is easy if [] is a HsVar with the right DataCon inside. +However, the type-checking for explicit lists works differently: [x,y,z] is never +polymorphic. Instead, we unify the types of x, y, and z together, and use the +unified type as the argument to the cons and nil constructors. Thus, treating +[] as an empty ExplicitList in the type-checker would prevent [] @Int from working. + +However, if -XOverloadedLists is on, then [] @Int really shouldn't be allowed: +it's just like fromListN 0 [] @Int. Since + fromListN :: forall list. IsList list => Int -> [Item list] -> list +that expression really should be rejected. Thus, the renamer's behaviour is +exactly what we want: treat [] as a datacon when -XNoOverloadedLists, and as +an empty ExplicitList when -XOverloadedLists. + +See also #13680, which requested [] @Int to work. +-} + + +----------------------- +pprExternalSrcLoc :: (StringLiteral,(Int,Int),(Int,Int)) -> SDoc +pprExternalSrcLoc (StringLiteral _ src,(n1,n2),(n3,n4)) + = ppr (src,(n1,n2),(n3,n4)) + +{- +HsSyn records exactly where the user put parens, with HsPar. +So generally speaking we print without adding any parens. +However, some code is internally generated, and in some places +parens are absolutely required; so for these places we use +pprParendLExpr (but don't print double parens of course). + +For operator applications we don't add parens, because the operator +fixities should do the job, except in debug mode (-dppr-debug) so we +can see the structure of the parse tree. +-} + +{- +************************************************************************ +* * +\subsection{Commands (in arrow abstractions)} +* * +************************************************************************ + +We re-use HsExpr to represent these. +-} + +-- | Located Haskell Command (for arrow syntax) +type LHsCmd id = XRec id (HsCmd id) + +-- | Haskell Command (e.g. a "statement" in an Arrow proc block) +data HsCmd id + -- | - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.Annlarrowtail', + -- 'GHC.Parser.Annotation.Annrarrowtail','GHC.Parser.Annotation.AnnLarrowtail', + -- 'GHC.Parser.Annotation.AnnRarrowtail' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + = HsCmdArrApp -- Arrow tail, or arrow application (f -< arg) + (XCmdArrApp id) -- type of the arrow expressions f, + -- of the form a t t', where arg :: t + (LHsExpr id) -- arrow expression, f + (LHsExpr id) -- input expression, arg + HsArrAppType -- higher-order (-<<) or first-order (-<) + Bool -- True => right-to-left (f -< arg) + -- False => left-to-right (arg >- f) + + -- | - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpenB' @'(|'@, + -- 'GHC.Parser.Annotation.AnnCloseB' @'|)'@ + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | HsCmdArrForm -- Command formation, (| e cmd1 .. cmdn |) + (XCmdArrForm id) + (LHsExpr id) -- The operator. + -- After type-checking, a type abstraction to be + -- applied to the type of the local environment tuple + LexicalFixity -- Whether the operator appeared prefix or infix when + -- parsed. + (Maybe Fixity) -- fixity (filled in by the renamer), for forms that + -- were converted from OpApp's by the renamer + [LHsCmdTop id] -- argument commands + + | HsCmdApp (XCmdApp id) + (LHsCmd id) + (LHsExpr id) + + | HsCmdLam (XCmdLam id) + (MatchGroup id (LHsCmd id)) -- kappa + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnLam', + -- 'GHC.Parser.Annotation.AnnRarrow', + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | HsCmdPar (XCmdPar id) + (LHsCmd id) -- parenthesised command + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @'('@, + -- 'GHC.Parser.Annotation.AnnClose' @')'@ + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | HsCmdCase (XCmdCase id) + (LHsExpr id) + (MatchGroup id (LHsCmd id)) -- bodies are HsCmd's + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnCase', + -- 'GHC.Parser.Annotation.AnnOf','GHC.Parser.Annotation.AnnOpen' @'{'@, + -- 'GHC.Parser.Annotation.AnnClose' @'}'@ + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | HsCmdLamCase (XCmdLamCase id) + (MatchGroup id (LHsCmd id)) -- bodies are HsCmd's + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnLam', + -- 'GHC.Parser.Annotation.AnnCase','GHC.Parser.Annotation.AnnOpen' @'{'@, + -- 'GHC.Parser.Annotation.AnnClose' @'}'@ + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | HsCmdIf (XCmdIf id) + (SyntaxExpr id) -- cond function + (LHsExpr id) -- predicate + (LHsCmd id) -- then part + (LHsCmd id) -- else part + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnIf', + -- 'GHC.Parser.Annotation.AnnSemi', + -- 'GHC.Parser.Annotation.AnnThen','GHC.Parser.Annotation.AnnSemi', + -- 'GHC.Parser.Annotation.AnnElse', + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | HsCmdLet (XCmdLet id) + (LHsLocalBinds id) -- let(rec) + (LHsCmd id) + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnLet', + -- 'GHC.Parser.Annotation.AnnOpen' @'{'@, + -- 'GHC.Parser.Annotation.AnnClose' @'}'@,'GHC.Parser.Annotation.AnnIn' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | HsCmdDo (XCmdDo id) -- Type of the whole expression + (XRec id [CmdLStmt id]) + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnDo', + -- 'GHC.Parser.Annotation.AnnOpen', 'GHC.Parser.Annotation.AnnSemi', + -- 'GHC.Parser.Annotation.AnnVbar', + -- 'GHC.Parser.Annotation.AnnClose' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | XCmd !(XXCmd id) -- Note [Trees that Grow] extension point + + +-- | Haskell Array Application Type +data HsArrAppType = HsHigherOrderApp | HsFirstOrderApp + deriving Data + + +{- | Top-level command, introducing a new arrow. +This may occur inside a proc (where the stack is empty) or as an +argument of a command-forming operator. +-} + +-- | Located Haskell Top-level Command +type LHsCmdTop p = XRec p (HsCmdTop p) + +-- | Haskell Top-level Command +data HsCmdTop p + = HsCmdTop (XCmdTop p) + (LHsCmd p) + | XCmdTop !(XXCmdTop p) -- Note [Trees that Grow] extension point + +----------------------- + +{- +************************************************************************ +* * +\subsection{Record binds} +* * +************************************************************************ +-} + +-- | Haskell Record Bindings +type HsRecordBinds p = HsRecFields p (LHsExpr p) + +{- +************************************************************************ +* * +\subsection{@Match@, @GRHSs@, and @GRHS@ datatypes} +* * +************************************************************************ + +@Match@es are sets of pattern bindings and right hand sides for +functions, patterns or case branches. For example, if a function @g@ +is defined as: +\begin{verbatim} +g (x,y) = y +g ((x:ys),y) = y+1, +\end{verbatim} +then \tr{g} has two @Match@es: @(x,y) = y@ and @((x:ys),y) = y+1@. + +It is always the case that each element of an @[Match]@ list has the +same number of @pats@s inside it. This corresponds to saying that +a function defined by pattern matching must have the same number of +patterns in each equation. +-} + +data MatchGroup p body + = MG { mg_ext :: XMG p body -- Post-typechecker, types of args and result + , mg_alts :: XRec p [LMatch p body] -- The alternatives + , mg_origin :: Origin } + -- The type is the type of the entire group + -- t1 -> ... -> tn -> tr + -- where there are n patterns + | XMatchGroup !(XXMatchGroup p body) + +data MatchGroupTc + = MatchGroupTc + { mg_arg_tys :: [Scaled Type] -- Types of the arguments, t1..tn + , mg_res_ty :: Type -- Type of the result, tr + } deriving Data + +-- | Located Match +type LMatch id body = XRec id (Match id body) +-- ^ May have 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnSemi' when in a +-- list + +-- For details on above see note [Api annotations] in GHC.Parser.Annotation +data Match p body + = Match { + m_ext :: XCMatch p body, + m_ctxt :: HsMatchContext (NoGhcTc p), + -- See note [m_ctxt in Match] + m_pats :: [LPat p], -- The patterns + m_grhss :: (GRHSs p body) + } + | XMatch !(XXMatch p body) + +{- +Note [m_ctxt in Match] +~~~~~~~~~~~~~~~~~~~~~~ + +A Match can occur in a number of contexts, such as a FunBind, HsCase, HsLam and +so on. + +In order to simplify tooling processing and pretty print output, the provenance +is captured in an HsMatchContext. + +This is particularly important for the API Annotations for a multi-equation +FunBind. + +The parser initially creates a FunBind with a single Match in it for +every function definition it sees. + +These are then grouped together by getMonoBind into a single FunBind, +where all the Matches are combined. + +In the process, all the original FunBind fun_id's bar one are +discarded, including the locations. + +This causes a problem for source to source conversions via API +Annotations, so the original fun_ids and infix flags are preserved in +the Match, when it originates from a FunBind. + +Example infix function definition requiring individual API Annotations + + (&&& ) [] [] = [] + xs &&& [] = xs + ( &&& ) [] ys = ys + + + +-} + + +isInfixMatch :: Match id body -> Bool +isInfixMatch match = case m_ctxt match of + FunRhs {mc_fixity = Infix} -> True + _ -> False + +-- | Guarded Right-Hand Sides +-- +-- GRHSs are used both for pattern bindings and for Matches +-- +-- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnVbar', +-- 'GHC.Parser.Annotation.AnnEqual','GHC.Parser.Annotation.AnnWhere', +-- 'GHC.Parser.Annotation.AnnOpen','GHC.Parser.Annotation.AnnClose' +-- 'GHC.Parser.Annotation.AnnRarrow','GHC.Parser.Annotation.AnnSemi' + +-- For details on above see note [Api annotations] in GHC.Parser.Annotation +data GRHSs p body + = GRHSs { + grhssExt :: XCGRHSs p body, + grhssGRHSs :: [LGRHS p body], -- ^ Guarded RHSs + grhssLocalBinds :: LHsLocalBinds p -- ^ The where clause + } + | XGRHSs !(XXGRHSs p body) + +-- | Located Guarded Right-Hand Side +type LGRHS id body = XRec id (GRHS id body) + +-- | Guarded Right Hand Side. +data GRHS p body = GRHS (XCGRHS p body) + [GuardLStmt p] -- Guards + body -- Right hand side + | XGRHS !(XXGRHS p body) + +-- We know the list must have at least one @Match@ in it. + +{- +************************************************************************ +* * +\subsection{Do stmts and list comprehensions} +* * +************************************************************************ +-} + +-- | Located @do@ block Statement +type LStmt id body = XRec id (StmtLR id id body) + +-- | Located Statement with separate Left and Right id's +type LStmtLR idL idR body = XRec idL (StmtLR idL idR body) + +-- | @do@ block Statement +type Stmt id body = StmtLR id id body + +-- | Command Located Statement +type CmdLStmt id = LStmt id (LHsCmd id) + +-- | Command Statement +type CmdStmt id = Stmt id (LHsCmd id) + +-- | Expression Located Statement +type ExprLStmt id = LStmt id (LHsExpr id) + +-- | Expression Statement +type ExprStmt id = Stmt id (LHsExpr id) + +-- | Guard Located Statement +type GuardLStmt id = LStmt id (LHsExpr id) + +-- | Guard Statement +type GuardStmt id = Stmt id (LHsExpr id) + +-- | Ghci Located Statement +type GhciLStmt id = LStmt id (LHsExpr id) + +-- | Ghci Statement +type GhciStmt id = Stmt id (LHsExpr id) + +-- The SyntaxExprs in here are used *only* for do-notation and monad +-- comprehensions, which have rebindable syntax. Otherwise they are unused. +-- | API Annotations when in qualifier lists or guards +-- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnVbar', +-- 'GHC.Parser.Annotation.AnnComma','GHC.Parser.Annotation.AnnThen', +-- 'GHC.Parser.Annotation.AnnBy','GHC.Parser.Annotation.AnnBy', +-- 'GHC.Parser.Annotation.AnnGroup','GHC.Parser.Annotation.AnnUsing' + +-- For details on above see note [Api annotations] in GHC.Parser.Annotation +data StmtLR idL idR body -- body should always be (LHs**** idR) + = LastStmt -- Always the last Stmt in ListComp, MonadComp, + -- and (after the renamer, see GHC.Rename.Expr.checkLastStmt) DoExpr, MDoExpr + -- Not used for GhciStmtCtxt, PatGuard, which scope over other stuff + (XLastStmt idL idR body) + body + (Maybe Bool) -- Whether return was stripped + -- Just True <=> return with a dollar was stripped by ApplicativeDo + -- Just False <=> return without a dollar was stripped by ApplicativeDo + -- Nothing <=> Nothing was stripped + (SyntaxExpr idR) -- The return operator + -- The return operator is used only for MonadComp + -- For ListComp we use the baked-in 'return' + -- For DoExpr, MDoExpr, we don't apply a 'return' at all + -- See Note [Monad Comprehensions] + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnLarrow' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | BindStmt (XBindStmt idL idR body) + -- ^ Post renaming has optional fail and bind / (>>=) operator. + -- Post typechecking, also has multiplicity of the argument + -- and the result type of the function passed to bind; + -- that is, (P, S) in (>>=) :: Q -> (R # P -> S) -> T + -- See Note [The type of bind in Stmts] + (LPat idL) + body + + -- | 'ApplicativeStmt' represents an applicative expression built with + -- '<$>' and '<*>'. It is generated by the renamer, and is desugared into the + -- appropriate applicative expression by the desugarer, but it is intended + -- to be invisible in error messages. + -- + -- For full details, see Note [ApplicativeDo] in "GHC.Rename.Expr" + -- + | ApplicativeStmt + (XApplicativeStmt idL idR body) -- Post typecheck, Type of the body + [ ( SyntaxExpr idR + , ApplicativeArg idL) ] + -- [(<$>, e1), (<*>, e2), ..., (<*>, en)] + (Maybe (SyntaxExpr idR)) -- 'join', if necessary + + | BodyStmt (XBodyStmt idL idR body) -- Post typecheck, element type + -- of the RHS (used for arrows) + body -- See Note [BodyStmt] + (SyntaxExpr idR) -- The (>>) operator + (SyntaxExpr idR) -- The `guard` operator; used only in MonadComp + -- See notes [Monad Comprehensions] + + -- | - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnLet' + -- 'GHC.Parser.Annotation.AnnOpen' @'{'@,'GHC.Parser.Annotation.AnnClose' @'}'@, + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | LetStmt (XLetStmt idL idR body) (LHsLocalBindsLR idL idR) + + -- ParStmts only occur in a list/monad comprehension + | ParStmt (XParStmt idL idR body) -- Post typecheck, + -- S in (>>=) :: Q -> (R -> S) -> T + [ParStmtBlock idL idR] + (HsExpr idR) -- Polymorphic `mzip` for monad comprehensions + (SyntaxExpr idR) -- The `>>=` operator + -- See notes [Monad Comprehensions] + -- After renaming, the ids are the binders + -- bound by the stmts and used after themp + + | TransStmt { + trS_ext :: XTransStmt idL idR body, -- Post typecheck, + -- R in (>>=) :: Q -> (R -> S) -> T + trS_form :: TransForm, + trS_stmts :: [ExprLStmt idL], -- Stmts to the *left* of the 'group' + -- which generates the tuples to be grouped + + trS_bndrs :: [(IdP idR, IdP idR)], -- See Note [TransStmt binder map] + + trS_using :: LHsExpr idR, + trS_by :: Maybe (LHsExpr idR), -- "by e" (optional) + -- Invariant: if trS_form = GroupBy, then grp_by = Just e + + trS_ret :: SyntaxExpr idR, -- The monomorphic 'return' function for + -- the inner monad comprehensions + trS_bind :: SyntaxExpr idR, -- The '(>>=)' operator + trS_fmap :: HsExpr idR -- The polymorphic 'fmap' function for desugaring + -- Only for 'group' forms + -- Just a simple HsExpr, because it's + -- too polymorphic for tcSyntaxOp + } -- See Note [Monad Comprehensions] + + -- Recursive statement (see Note [How RecStmt works] below) + -- | - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnRec' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | RecStmt + { recS_ext :: XRecStmt idL idR body + , recS_stmts :: [LStmtLR idL idR body] + + -- The next two fields are only valid after renaming + , recS_later_ids :: [IdP idR] + -- The ids are a subset of the variables bound by the + -- stmts that are used in stmts that follow the RecStmt + + , recS_rec_ids :: [IdP idR] + -- Ditto, but these variables are the "recursive" ones, + -- that are used before they are bound in the stmts of + -- the RecStmt. + -- An Id can be in both groups + -- Both sets of Ids are (now) treated monomorphically + -- See Note [How RecStmt works] for why they are separate + + -- Rebindable syntax + , recS_bind_fn :: SyntaxExpr idR -- The bind function + , recS_ret_fn :: SyntaxExpr idR -- The return function + , recS_mfix_fn :: SyntaxExpr idR -- The mfix function + } + | XStmtLR !(XXStmtLR idL idR body) + +data TransForm -- The 'f' below is the 'using' function, 'e' is the by function + = ThenForm -- then f or then f by e (depending on trS_by) + | GroupForm -- then group using f or then group by e using f (depending on trS_by) + deriving Data + +-- | Parenthesised Statement Block +data ParStmtBlock idL idR + = ParStmtBlock + (XParStmtBlock idL idR) + [ExprLStmt idL] + [IdP idR] -- The variables to be returned + (SyntaxExpr idR) -- The return operator + | XParStmtBlock !(XXParStmtBlock idL idR) + +-- | The fail operator +-- +-- This is used for `.. <-` "bind statments" in do notation, including +-- non-monadic "binds" in applicative. +-- +-- The fail operator is 'Just expr' if it potentially fail monadically. if the +-- pattern match cannot fail, or shouldn't fail monadically (regular incomplete +-- pattern exception), it is 'Nothing'. +-- +-- See Note [Monad fail : Rebindable syntax, overloaded strings] for the type of +-- expression in the 'Just' case, and why it is so. +-- +-- See Note [Failing pattern matches in Stmts] for which contexts for +-- '@BindStmt@'s should use the monadic fail and which shouldn't. +type FailOperator id = Maybe (SyntaxExpr id) + +-- | Applicative Argument +data ApplicativeArg idL + = ApplicativeArgOne -- A single statement (BindStmt or BodyStmt) + { xarg_app_arg_one :: XApplicativeArgOne idL + -- ^ The fail operator, after renaming + -- + -- The fail operator is needed if this is a BindStmt + -- where the pattern can fail. E.g.: + -- (Just a) <- stmt + -- The fail operator will be invoked if the pattern + -- match fails. + -- It is also used for guards in MonadComprehensions. + -- The fail operator is Nothing + -- if the pattern match can't fail + , app_arg_pattern :: LPat idL -- WildPat if it was a BodyStmt (see below) + , arg_expr :: LHsExpr idL + , is_body_stmt :: Bool + -- ^ True <=> was a BodyStmt, + -- False <=> was a BindStmt. + -- See Note [Applicative BodyStmt] + } + | ApplicativeArgMany -- do { stmts; return vars } + { xarg_app_arg_many :: XApplicativeArgMany idL + , app_stmts :: [ExprLStmt idL] -- stmts + , final_expr :: HsExpr idL -- return (v1,..,vn), or just (v1,..,vn) + , bv_pattern :: LPat idL -- (v1,...,vn) + , stmt_context :: HsStmtContext (ApplicativeArgStmCtxPass idL) + -- ^ context of the do expression, used in pprArg + } + | XApplicativeArg !(XXApplicativeArg idL) + +type family ApplicativeArgStmCtxPass idL + +{- +Note [The type of bind in Stmts] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Some Stmts, notably BindStmt, keep the (>>=) bind operator. +We do NOT assume that it has type + (>>=) :: m a -> (a -> m b) -> m b +In some cases (see #303, #1537) it might have a more +exotic type, such as + (>>=) :: m i j a -> (a -> m j k b) -> m i k b +So we must be careful not to make assumptions about the type. +In particular, the monad may not be uniform throughout. + +Note [TransStmt binder map] +~~~~~~~~~~~~~~~~~~~~~~~~~~~ +The [(idR,idR)] in a TransStmt behaves as follows: + + * Before renaming: [] + + * After renaming: + [ (x27,x27), ..., (z35,z35) ] + These are the variables + bound by the stmts to the left of the 'group' + and used either in the 'by' clause, + or in the stmts following the 'group' + Each item is a pair of identical variables. + + * After typechecking: + [ (x27:Int, x27:[Int]), ..., (z35:Bool, z35:[Bool]) ] + Each pair has the same unique, but different *types*. + +Note [BodyStmt] +~~~~~~~~~~~~~~~ +BodyStmts are a bit tricky, because what they mean +depends on the context. Consider the following contexts: + + A do expression of type (m res_ty) + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + * BodyStmt E any_ty: do { ....; E; ... } + E :: m any_ty + Translation: E >> ... + + A list comprehensions of type [elt_ty] + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + * BodyStmt E Bool: [ .. | .... E ] + [ .. | ..., E, ... ] + [ .. | .... | ..., E | ... ] + E :: Bool + Translation: if E then fail else ... + + A guard list, guarding a RHS of type rhs_ty + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + * BodyStmt E BooParStmtBlockl: f x | ..., E, ... = ...rhs... + E :: Bool + Translation: if E then fail else ... + + A monad comprehension of type (m res_ty) + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + * BodyStmt E Bool: [ .. | .... E ] + E :: Bool + Translation: guard E >> ... + +Array comprehensions are handled like list comprehensions. + +Note [How RecStmt works] +~~~~~~~~~~~~~~~~~~~~~~~~ +Example: + HsDo [ BindStmt x ex + + , RecStmt { recS_rec_ids = [a, c] + , recS_stmts = [ BindStmt b (return (a,c)) + , LetStmt a = ...b... + , BindStmt c ec ] + , recS_later_ids = [a, b] + + , return (a b) ] + +Here, the RecStmt binds a,b,c; but + - Only a,b are used in the stmts *following* the RecStmt, + - Only a,c are used in the stmts *inside* the RecStmt + *before* their bindings + +Why do we need *both* rec_ids and later_ids? For monads they could be +combined into a single set of variables, but not for arrows. That +follows from the types of the respective feedback operators: + + mfix :: MonadFix m => (a -> m a) -> m a + loop :: ArrowLoop a => a (b,d) (c,d) -> a b c + +* For mfix, the 'a' covers the union of the later_ids and the rec_ids +* For 'loop', 'c' is the later_ids and 'd' is the rec_ids + +Note [Typing a RecStmt] +~~~~~~~~~~~~~~~~~~~~~~~ +A (RecStmt stmts) types as if you had written + + (v1,..,vn, _, ..., _) <- mfix (\~(_, ..., _, r1, ..., rm) -> + do { stmts + ; return (v1,..vn, r1, ..., rm) }) + +where v1..vn are the later_ids + r1..rm are the rec_ids + +Note [Monad Comprehensions] +~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Monad comprehensions require separate functions like 'return' and +'>>=' for desugaring. These functions are stored in the statements +used in monad comprehensions. For example, the 'return' of the 'LastStmt' +expression is used to lift the body of the monad comprehension: + + [ body | stmts ] + => + stmts >>= \bndrs -> return body + +In transform and grouping statements ('then ..' and 'then group ..') the +'return' function is required for nested monad comprehensions, for example: + + [ body | stmts, then f, rest ] + => + f [ env | stmts ] >>= \bndrs -> [ body | rest ] + +BodyStmts require the 'Control.Monad.guard' function for boolean +expressions: + + [ body | exp, stmts ] + => + guard exp >> [ body | stmts ] + +Parallel statements require the 'Control.Monad.Zip.mzip' function: + + [ body | stmts1 | stmts2 | .. ] + => + mzip stmts1 (mzip stmts2 (..)) >>= \(bndrs1, (bndrs2, ..)) -> return body + +In any other context than 'MonadComp', the fields for most of these +'SyntaxExpr's stay bottom. + + +Note [Applicative BodyStmt] + +(#12143) For the purposes of ApplicativeDo, we treat any BodyStmt +as if it was a BindStmt with a wildcard pattern. For example, + + do + x <- A + B + return x + +is transformed as if it were + + do + x <- A + _ <- B + return x + +so it transforms to + + (\(x,_) -> x) <$> A <*> B + +But we have to remember when we treat a BodyStmt like a BindStmt, +because in error messages we want to emit the original syntax the user +wrote, not our internal representation. So ApplicativeArgOne has a +Bool flag that is True when the original statement was a BodyStmt, so +that we can pretty-print it correctly. +-} + + +{- +************************************************************************ +* * + Template Haskell quotation brackets +* * +************************************************************************ +-} + +-- | Haskell Splice +data HsSplice id + = HsTypedSplice -- $$z or $$(f 4) + (XTypedSplice id) + SpliceDecoration -- Whether $$( ) variant found, for pretty printing + (IdP id) -- A unique name to identify this splice point + (LHsExpr id) -- See Note [Pending Splices] + + | HsUntypedSplice -- $z or $(f 4) + (XUntypedSplice id) + SpliceDecoration -- Whether $( ) variant found, for pretty printing + (IdP id) -- A unique name to identify this splice point + (LHsExpr id) -- See Note [Pending Splices] + + | HsQuasiQuote -- See Note [Quasi-quote overview] in GHC.Tc.Gen.Splice + (XQuasiQuote id) + (IdP id) -- Splice point + (IdP id) -- Quoter + SrcSpan -- The span of the enclosed string + FastString -- The enclosed string + + -- AZ:TODO: use XSplice instead of HsSpliced + | HsSpliced -- See Note [Delaying modFinalizers in untyped splices] in + -- GHC.Rename.Splice. + -- This is the result of splicing a splice. It is produced by + -- the renamer and consumed by the typechecker. It lives only + -- between the two. + (XSpliced id) + ThModFinalizers -- TH finalizers produced by the splice. + (HsSplicedThing id) -- The result of splicing + | XSplice !(XXSplice id) -- Note [Trees that Grow] extension point + +-- | A splice can appear with various decorations wrapped around it. This data +-- type captures explicitly how it was originally written, for use in the pretty +-- printer. +data SpliceDecoration + = DollarSplice -- ^ $splice or $$splice + | BareSplice -- ^ bare splice + deriving (Data, Eq, Show) + +instance Outputable SpliceDecoration where + ppr x = text $ show x + + +isTypedSplice :: HsSplice id -> Bool +isTypedSplice (HsTypedSplice {}) = True +isTypedSplice _ = False -- Quasi-quotes are untyped splices + +-- | Finalizers produced by a splice with +-- 'Language.Haskell.TH.Syntax.addModFinalizer' +-- +-- See Note [Delaying modFinalizers in untyped splices] in GHC.Rename.Splice. For how +-- this is used. +-- +newtype ThModFinalizers = ThModFinalizers [ForeignRef (TH.Q ())] + +-- A Data instance which ignores the argument of 'ThModFinalizers'. +instance Data ThModFinalizers where + gunfold _ z _ = z $ ThModFinalizers [] + toConstr a = mkConstr (dataTypeOf a) "ThModFinalizers" [] Data.Prefix + dataTypeOf a = mkDataType "HsExpr.ThModFinalizers" [toConstr a] + +-- | Haskell Spliced Thing +-- +-- Values that can result from running a splice. +data HsSplicedThing id + = HsSplicedExpr (HsExpr id) -- ^ Haskell Spliced Expression + | HsSplicedTy (HsType id) -- ^ Haskell Spliced Type + | HsSplicedPat (Pat id) -- ^ Haskell Spliced Pattern + + +-- See Note [Pending Splices] +type SplicePointName = Name + +data UntypedSpliceFlavour + = UntypedExpSplice + | UntypedPatSplice + | UntypedTypeSplice + | UntypedDeclSplice + deriving Data + +-- | Haskell Bracket +data HsBracket p + = ExpBr (XExpBr p) (LHsExpr p) -- [| expr |] + | PatBr (XPatBr p) (LPat p) -- [p| pat |] + | DecBrL (XDecBrL p) [LHsDecl p] -- [d| decls |]; result of parser + | DecBrG (XDecBrG p) (HsGroup p) -- [d| decls |]; result of renamer + | TypBr (XTypBr p) (LHsType p) -- [t| type |] + | VarBr (XVarBr p) Bool (IdP p) -- True: 'x, False: ''T + -- (The Bool flag is used only in pprHsBracket) + | TExpBr (XTExpBr p) (LHsExpr p) -- [|| expr ||] + | XBracket !(XXBracket p) -- Note [Trees that Grow] extension point + +isTypedBracket :: HsBracket id -> Bool +isTypedBracket (TExpBr {}) = True +isTypedBracket _ = False + +{- +************************************************************************ +* * +\subsection{Enumerations and list comprehensions} +* * +************************************************************************ +-} + +-- | Arithmetic Sequence Information +data ArithSeqInfo id + = From (LHsExpr id) + | FromThen (LHsExpr id) + (LHsExpr id) + | FromTo (LHsExpr id) + (LHsExpr id) + | FromThenTo (LHsExpr id) + (LHsExpr id) + (LHsExpr id) +-- AZ: Should ArithSeqInfo have a TTG extension? + +{- +************************************************************************ +* * +\subsection{HsMatchCtxt} +* * +************************************************************************ +-} + +-- | Haskell Match Context +-- +-- Context of a pattern match. This is more subtle than it would seem. See Note +-- [Varieties of pattern matches]. +data HsMatchContext p + = FunRhs { mc_fun :: LIdP p -- ^ function binder of @f@ + , mc_fixity :: LexicalFixity -- ^ fixing of @f@ + , mc_strictness :: SrcStrictness -- ^ was @f@ banged? + -- See Note [FunBind vs PatBind] + } + -- ^A pattern matching on an argument of a + -- function binding + | LambdaExpr -- ^Patterns of a lambda + | CaseAlt -- ^Patterns and guards on a case alternative + | IfAlt -- ^Guards of a multi-way if alternative + | ProcExpr -- ^Patterns of a proc + | PatBindRhs -- ^A pattern binding eg [y] <- e = e + | PatBindGuards -- ^Guards of pattern bindings, e.g., + -- (Just b) | Just _ <- x = e + -- | otherwise = e' + + | RecUpd -- ^Record update [used only in GHC.HsToCore.Expr to + -- tell matchWrapper what sort of + -- runtime error message to generate] + + | StmtCtxt (HsStmtContext p) -- ^Pattern of a do-stmt, list comprehension, + -- pattern guard, etc + + | ThPatSplice -- ^A Template Haskell pattern splice + | ThPatQuote -- ^A Template Haskell pattern quotation [p| (a,b) |] + | PatSyn -- ^A pattern synonym declaration + +isPatSynCtxt :: HsMatchContext p -> Bool +isPatSynCtxt ctxt = + case ctxt of + PatSyn -> True + _ -> False + +-- | Haskell Statement Context. +data HsStmtContext p + = ListComp + | MonadComp + + | DoExpr (Maybe ModuleName) -- ^[ModuleName.]do { ... } + | MDoExpr (Maybe ModuleName) -- ^[ModuleName.]mdo { ... } ie recursive do-expression + | ArrowExpr -- ^do-notation in an arrow-command context + + | GhciStmtCtxt -- ^A command-line Stmt in GHCi pat <- rhs + | PatGuard (HsMatchContext p) -- ^Pattern guard for specified thing + | ParStmtCtxt (HsStmtContext p) -- ^A branch of a parallel stmt + | TransStmtCtxt (HsStmtContext p) -- ^A branch of a transform stmt + +qualifiedDoModuleName_maybe :: HsStmtContext p -> Maybe ModuleName +qualifiedDoModuleName_maybe ctxt = case ctxt of + DoExpr m -> m + MDoExpr m -> m + _ -> Nothing + +isComprehensionContext :: HsStmtContext id -> Bool +-- Uses comprehension syntax [ e | quals ] +isComprehensionContext ListComp = True +isComprehensionContext MonadComp = True +isComprehensionContext (ParStmtCtxt c) = isComprehensionContext c +isComprehensionContext (TransStmtCtxt c) = isComprehensionContext c +isComprehensionContext _ = False + +-- | Is this a monadic context? +isMonadStmtContext :: HsStmtContext id -> Bool +isMonadStmtContext MonadComp = True +isMonadStmtContext DoExpr{} = True +isMonadStmtContext MDoExpr{} = True +isMonadStmtContext GhciStmtCtxt = True +isMonadStmtContext (ParStmtCtxt ctxt) = isMonadStmtContext ctxt +isMonadStmtContext (TransStmtCtxt ctxt) = isMonadStmtContext ctxt +isMonadStmtContext _ = False -- ListComp, PatGuard, ArrowExpr + +isMonadCompContext :: HsStmtContext id -> Bool +isMonadCompContext MonadComp = True +isMonadCompContext _ = False + +matchSeparator :: HsMatchContext p -> SDoc +matchSeparator (FunRhs {}) = text "=" +matchSeparator CaseAlt = text "->" +matchSeparator IfAlt = text "->" +matchSeparator LambdaExpr = text "->" +matchSeparator ProcExpr = text "->" +matchSeparator PatBindRhs = text "=" +matchSeparator PatBindGuards = text "=" +matchSeparator (StmtCtxt _) = text "<-" +matchSeparator RecUpd = text "=" -- This can be printed by the pattern + -- match checker trace +matchSeparator ThPatSplice = panic "unused" +matchSeparator ThPatQuote = panic "unused" +matchSeparator PatSyn = panic "unused" + +pprMatchContext :: (Outputable (IdP p), UnXRec p) + => HsMatchContext p -> SDoc +pprMatchContext ctxt + | want_an ctxt = text "an" <+> pprMatchContextNoun ctxt + | otherwise = text "a" <+> pprMatchContextNoun ctxt + where + want_an (FunRhs {}) = True -- Use "an" in front + want_an ProcExpr = True + want_an _ = False + +pprMatchContextNoun :: forall p. (Outputable (IdP p), UnXRec p) + => HsMatchContext p -> SDoc +pprMatchContextNoun (FunRhs {mc_fun=fun}) + = text "equation for" + <+> quotes (ppr (unXRec @p fun)) +pprMatchContextNoun CaseAlt = text "case alternative" +pprMatchContextNoun IfAlt = text "multi-way if alternative" +pprMatchContextNoun RecUpd = text "record-update construct" +pprMatchContextNoun ThPatSplice = text "Template Haskell pattern splice" +pprMatchContextNoun ThPatQuote = text "Template Haskell pattern quotation" +pprMatchContextNoun PatBindRhs = text "pattern binding" +pprMatchContextNoun PatBindGuards = text "pattern binding guards" +pprMatchContextNoun LambdaExpr = text "lambda abstraction" +pprMatchContextNoun ProcExpr = text "arrow abstraction" +pprMatchContextNoun (StmtCtxt ctxt) = text "pattern binding in" + $$ pprAStmtContext ctxt +pprMatchContextNoun PatSyn = text "pattern synonym declaration" + +----------------- +pprAStmtContext, pprStmtContext :: (Outputable (IdP p), UnXRec p) + => HsStmtContext p -> SDoc +pprAStmtContext ctxt = article <+> pprStmtContext ctxt + where + pp_an = text "an" + pp_a = text "a" + article = case ctxt of + MDoExpr Nothing -> pp_an + GhciStmtCtxt -> pp_an + _ -> pp_a + + +----------------- +pprStmtContext GhciStmtCtxt = text "interactive GHCi command" +pprStmtContext (DoExpr m) = prependQualified m (text "'do' block") +pprStmtContext (MDoExpr m) = prependQualified m (text "'mdo' block") +pprStmtContext ArrowExpr = text "'do' block in an arrow command" +pprStmtContext ListComp = text "list comprehension" +pprStmtContext MonadComp = text "monad comprehension" +pprStmtContext (PatGuard ctxt) = text "pattern guard for" $$ pprMatchContext ctxt + +-- Drop the inner contexts when reporting errors, else we get +-- Unexpected transform statement +-- in a transformed branch of +-- transformed branch of +-- transformed branch of monad comprehension +pprStmtContext (ParStmtCtxt c) = + ifPprDebug (sep [text "parallel branch of", pprAStmtContext c]) + (pprStmtContext c) +pprStmtContext (TransStmtCtxt c) = + ifPprDebug (sep [text "transformed branch of", pprAStmtContext c]) + (pprStmtContext c) + +prependQualified :: Maybe ModuleName -> SDoc -> SDoc +prependQualified Nothing t = t +prependQualified (Just _) t = text "qualified" <+> t diff --git a/compiler/Language/Haskell/Syntax/Expr.hs-boot b/compiler/Language/Haskell/Syntax/Expr.hs-boot new file mode 100644 index 0000000000..3ea7e32708 --- /dev/null +++ b/compiler/Language/Haskell/Syntax/Expr.hs-boot @@ -0,0 +1,22 @@ +{-# LANGUAGE KindSignatures #-} +{-# LANGUAGE ConstraintKinds #-} +{-# LANGUAGE RoleAnnotations #-} +{-# LANGUAGE TypeFamilies #-} + +-- See Note [Language.Haskell.Syntax.* Hierarchy] for why not GHC.Hs.* +module Language.Haskell.Syntax.Expr where + +import Language.Haskell.Syntax.Extension ( XRec ) +import Data.Kind ( Type ) + +type role HsExpr nominal +type role MatchGroup nominal nominal +type role GRHSs nominal nominal +type role HsSplice nominal +data HsExpr (i :: Type) +data HsSplice (i :: Type) +data MatchGroup (a :: Type) (body :: Type) +data GRHSs (a :: Type) (body :: Type) +type family SyntaxExpr (i :: Type) + +type LHsExpr a = XRec a (HsExpr a) diff --git a/compiler/Language/Haskell/Syntax/Extension.hs b/compiler/Language/Haskell/Syntax/Extension.hs new file mode 100644 index 0000000000..16b11b3e30 --- /dev/null +++ b/compiler/Language/Haskell/Syntax/Extension.hs @@ -0,0 +1,665 @@ +{-# LANGUAGE AllowAmbiguousTypes #-} -- for unXRec, etc. +{-# LANGUAGE ConstraintKinds #-} +{-# LANGUAGE DataKinds #-} +{-# LANGUAGE DeriveDataTypeable #-} +{-# LANGUAGE EmptyCase #-} +{-# LANGUAGE EmptyDataDeriving #-} +{-# LANGUAGE FlexibleContexts #-} +{-# LANGUAGE FlexibleInstances #-} +{-# LANGUAGE GADTs #-} +{-# LANGUAGE MultiParamTypeClasses #-} +{-# LANGUAGE RankNTypes #-} +{-# LANGUAGE ScopedTypeVariables #-} +{-# LANGUAGE TypeApplications #-} +{-# LANGUAGE TypeFamilyDependencies #-} +{-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow] + -- in module Language.Haskell.Syntax.Extension + +-- See Note [Language.Haskell.Syntax.* Hierarchy] for why not GHC.Hs.* +module Language.Haskell.Syntax.Extension where + +-- This module captures the type families to precisely identify the extension +-- points for GHC.Hs syntax + +import GHC.Prelude + +import Data.Data hiding ( Fixity ) +import Data.Kind (Type) +import GHC.Utils.Outputable + +{- +Note [Trees that grow] +~~~~~~~~~~~~~~~~~~~~~~ + +See https://gitlab.haskell.org/ghc/ghc/wikis/implementing-trees-that-grow + +The hsSyn AST is reused across multiple compiler passes. We also have the +Template Haskell AST, and the haskell-src-exts one (outside of GHC) + +Supporting multiple passes means the AST has various warts on it to cope with +the specifics for the phases, such as the 'ValBindsOut', 'ConPatOut', +'SigPatOut' etc. + +The growable AST will allow each of these variants to be captured explicitly, +such that they only exist in the given compiler pass AST, as selected by the +type parameter to the AST. + +In addition it will allow tool writers to define their own extensions to capture +additional information for the tool, in a natural way. + +A further goal is to provide a means to harmonise the Template Haskell and +haskell-src-exts ASTs as well. + +Wrinkle: In order to print out the AST, we need to know it is Outputable. +We also sometimes need to branch on the particular pass that we're in +(e.g. to print out type information once we know it). In order to allow +both of these actions, we define OutputableBndrId, which gathers the necessary +OutputableBndr and IsPass constraints. The use of this constraint in instances +generally requires UndecidableInstances. + +See also Note [IsPass] and Note [NoGhcTc] in GHC.Hs.Extension. + +-} + +-- | A placeholder type for TTG extension points that are not currently +-- unused to represent any particular value. +-- +-- This should not be confused with 'NoExtCon', which are found in unused +-- extension /constructors/ and therefore should never be inhabited. In +-- contrast, 'NoExtField' is used in extension /points/ (e.g., as the field of +-- some constructor), so it must have an inhabitant to construct AST passes +-- that manipulate fields with that extension point as their type. +data NoExtField = NoExtField + deriving (Data,Eq,Ord) + +instance Outputable NoExtField where + ppr _ = text "NoExtField" + +-- | Used when constructing a term with an unused extension point. +noExtField :: NoExtField +noExtField = NoExtField + +-- | Used in TTG extension constructors that have yet to be extended with +-- anything. If an extension constructor has 'NoExtCon' as its field, it is +-- not intended to ever be constructed anywhere, and any function that consumes +-- the extension constructor can eliminate it by way of 'noExtCon'. +-- +-- This should not be confused with 'NoExtField', which are found in unused +-- extension /points/ (not /constructors/) and therefore can be inhabited. + +-- See also [NoExtCon and strict fields]. +data NoExtCon + deriving (Data,Eq,Ord) + +instance Outputable NoExtCon where + ppr = noExtCon + +-- | Eliminate a 'NoExtCon'. Much like 'Data.Void.absurd'. +noExtCon :: NoExtCon -> a +noExtCon x = case x of {} + +-- | GHC's L prefixed variants wrap their vanilla variant in this type family, +-- to add 'SrcLoc' info via 'Located'. Other passes than 'GhcPass' not +-- interested in location information can define this as +-- @type instance XRec NoLocated a = a@. +-- See Note [XRec and SrcSpans in the AST] +type family XRec p a = r | r -> a + +{- +Note [XRec and SrcSpans in the AST] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +XRec is meant to replace most of the uses of `Located` in the AST. It is another +extension point meant to make it easier for non-GHC applications to reuse the +AST for their own purposes, and not have to deal the hassle of (perhaps) useless +SrcSpans everywhere. + +instead of `Located (HsExpr p)` or similar types, we will now have `XRec p +(HsExpr p)` + +XRec allows annotating certain points in the AST with extra information. This +maybe be source spans (for GHC), nothing (for TH), types (for HIE files), api +annotations (for exactprint) or anything else. + +This should hopefully bring us one step closer to sharing the AST between GHC +and TH. + +We use the `UnXRec`, `MapXRec` and `WrapXRec` type classes to aid us in writing +pass-polymorphic code that deals with `XRec`s +-} + +-- | We can strip off the XRec to access the underlying data. +-- See Note [XRec and SrcSpans in the AST] +class UnXRec p where + unXRec :: XRec p a -> a + +-- | We can map over the underlying type contained in an @XRec@ while preserving +-- the annotation as is. +-- See Note [XRec and SrcSpans in the AST] +class MapXRec p where + mapXRec :: (a -> b) -> XRec p a -> XRec p b + +-- | The trivial wrapper that carries no additional information +-- See Note [XRec and SrcSpans in the AST] +class WrapXRec p where + wrapXRec :: a -> XRec p a + +-- | Maps the "normal" id type for a given pass +type family IdP p + +type LIdP p = XRec p (IdP p) + +-- ===================================================================== +-- Type families for the HsBinds extension points + +-- HsLocalBindsLR type families +type family XHsValBinds x x' +type family XHsIPBinds x x' +type family XEmptyLocalBinds x x' +type family XXHsLocalBindsLR x x' + +-- HsValBindsLR type families +type family XValBinds x x' +type family XXValBindsLR x x' + +-- HsBindLR type families +type family XFunBind x x' +type family XPatBind x x' +type family XVarBind x x' +type family XAbsBinds x x' +type family XPatSynBind x x' +type family XXHsBindsLR x x' + +-- ABExport type families +type family XABE x +type family XXABExport x + +-- PatSynBind type families +type family XPSB x x' +type family XXPatSynBind x x' + +-- HsIPBinds type families +type family XIPBinds x +type family XXHsIPBinds x + +-- IPBind type families +type family XCIPBind x +type family XXIPBind x + +-- Sig type families +type family XTypeSig x +type family XPatSynSig x +type family XClassOpSig x +type family XIdSig x +type family XFixSig x +type family XInlineSig x +type family XSpecSig x +type family XSpecInstSig x +type family XMinimalSig x +type family XSCCFunSig x +type family XCompleteMatchSig x +type family XXSig x + +-- FixitySig type families +type family XFixitySig x +type family XXFixitySig x + +-- StandaloneKindSig type families +type family XStandaloneKindSig x +type family XXStandaloneKindSig x + +-- ===================================================================== +-- Type families for the HsDecls extension points + +-- HsDecl type families +type family XTyClD x +type family XInstD x +type family XDerivD x +type family XValD x +type family XSigD x +type family XKindSigD x +type family XDefD x +type family XForD x +type family XWarningD x +type family XAnnD x +type family XRuleD x +type family XSpliceD x +type family XDocD x +type family XRoleAnnotD x +type family XXHsDecl x + +-- ------------------------------------- +-- HsGroup type families +type family XCHsGroup x +type family XXHsGroup x + +-- ------------------------------------- +-- SpliceDecl type families +type family XSpliceDecl x +type family XXSpliceDecl x + +-- ------------------------------------- +-- TyClDecl type families +type family XFamDecl x +type family XSynDecl x +type family XDataDecl x +type family XClassDecl x +type family XXTyClDecl x + +-- ------------------------------------- +-- TyClGroup type families +type family XCTyClGroup x +type family XXTyClGroup x + +-- ------------------------------------- +-- FamilyResultSig type families +type family XNoSig x +type family XCKindSig x -- Clashes with XKindSig above +type family XTyVarSig x +type family XXFamilyResultSig x + +-- ------------------------------------- +-- FamilyDecl type families +type family XCFamilyDecl x +type family XXFamilyDecl x + +-- ------------------------------------- +-- HsDataDefn type families +type family XCHsDataDefn x +type family XXHsDataDefn x + +-- ------------------------------------- +-- HsDerivingClause type families +type family XCHsDerivingClause x +type family XXHsDerivingClause x + +-- ------------------------------------- +-- DerivClauseTys type families +type family XDctSingle x +type family XDctMulti x +type family XXDerivClauseTys x + +-- ------------------------------------- +-- ConDecl type families +type family XConDeclGADT x +type family XConDeclH98 x +type family XXConDecl x + +-- ------------------------------------- +-- FamEqn type families +type family XCFamEqn x r +type family XXFamEqn x r + +-- ------------------------------------- +-- ClsInstDecl type families +type family XCClsInstDecl x +type family XXClsInstDecl x + +-- ------------------------------------- +-- InstDecl type families +type family XClsInstD x +type family XDataFamInstD x +type family XTyFamInstD x +type family XXInstDecl x + +-- ------------------------------------- +-- DerivDecl type families +type family XCDerivDecl x +type family XXDerivDecl x + +-- ------------------------------------- +-- DerivStrategy type family +type family XViaStrategy x + +-- ------------------------------------- +-- DefaultDecl type families +type family XCDefaultDecl x +type family XXDefaultDecl x + +-- ------------------------------------- +-- ForeignDecl type families +type family XForeignImport x +type family XForeignExport x +type family XXForeignDecl x + +-- ------------------------------------- +-- RuleDecls type families +type family XCRuleDecls x +type family XXRuleDecls x + +-- ------------------------------------- +-- RuleDecl type families +type family XHsRule x +type family XXRuleDecl x + +-- ------------------------------------- +-- RuleBndr type families +type family XCRuleBndr x +type family XRuleBndrSig x +type family XXRuleBndr x + +-- ------------------------------------- +-- WarnDecls type families +type family XWarnings x +type family XXWarnDecls x + +-- ------------------------------------- +-- WarnDecl type families +type family XWarning x +type family XXWarnDecl x + +-- ------------------------------------- +-- AnnDecl type families +type family XHsAnnotation x +type family XXAnnDecl x + +-- ------------------------------------- +-- RoleAnnotDecl type families +type family XCRoleAnnotDecl x +type family XXRoleAnnotDecl x + +-- ===================================================================== +-- Type families for the HsExpr extension points + +type family XVar x +type family XUnboundVar x +type family XConLikeOut x +type family XRecFld x +type family XOverLabel x +type family XIPVar x +type family XOverLitE x +type family XLitE x +type family XLam x +type family XLamCase x +type family XApp x +type family XAppTypeE x +type family XOpApp x +type family XNegApp x +type family XPar x +type family XSectionL x +type family XSectionR x +type family XExplicitTuple x +type family XExplicitSum x +type family XCase x +type family XIf x +type family XMultiIf x +type family XLet x +type family XDo x +type family XExplicitList x +type family XRecordCon x +type family XRecordUpd x +type family XExprWithTySig x +type family XArithSeq x +type family XBracket x +type family XRnBracketOut x +type family XTcBracketOut x +type family XSpliceE x +type family XProc x +type family XStatic x +type family XTick x +type family XBinTick x +type family XPragE x +type family XXExpr x + +-- ------------------------------------- +-- HsPragE type families +type family XSCC x +type family XXPragE x + + +-- ------------------------------------- +-- AmbiguousFieldOcc type families +type family XUnambiguous x +type family XAmbiguous x +type family XXAmbiguousFieldOcc x + +-- ------------------------------------- +-- HsTupArg type families +type family XPresent x +type family XMissing x +type family XXTupArg x + +-- ------------------------------------- +-- HsSplice type families +type family XTypedSplice x +type family XUntypedSplice x +type family XQuasiQuote x +type family XSpliced x +type family XXSplice x + +-- ------------------------------------- +-- HsBracket type families +type family XExpBr x +type family XPatBr x +type family XDecBrL x +type family XDecBrG x +type family XTypBr x +type family XVarBr x +type family XTExpBr x +type family XXBracket x + +-- ------------------------------------- +-- HsCmdTop type families +type family XCmdTop x +type family XXCmdTop x + +-- ------------------------------------- +-- MatchGroup type families +type family XMG x b +type family XXMatchGroup x b + +-- ------------------------------------- +-- Match type families +type family XCMatch x b +type family XXMatch x b + +-- ------------------------------------- +-- GRHSs type families +type family XCGRHSs x b +type family XXGRHSs x b + +-- ------------------------------------- +-- GRHS type families +type family XCGRHS x b +type family XXGRHS x b + +-- ------------------------------------- +-- StmtLR type families +type family XLastStmt x x' b +type family XBindStmt x x' b +type family XApplicativeStmt x x' b +type family XBodyStmt x x' b +type family XLetStmt x x' b +type family XParStmt x x' b +type family XTransStmt x x' b +type family XRecStmt x x' b +type family XXStmtLR x x' b + +-- ------------------------------------- +-- HsCmd type families +type family XCmdArrApp x +type family XCmdArrForm x +type family XCmdApp x +type family XCmdLam x +type family XCmdPar x +type family XCmdCase x +type family XCmdLamCase x +type family XCmdIf x +type family XCmdLet x +type family XCmdDo x +type family XCmdWrap x +type family XXCmd x + +-- ------------------------------------- +-- ParStmtBlock type families +type family XParStmtBlock x x' +type family XXParStmtBlock x x' + +-- ------------------------------------- +-- ApplicativeArg type families +type family XApplicativeArgOne x +type family XApplicativeArgMany x +type family XXApplicativeArg x + +-- ===================================================================== +-- Type families for the HsImpExp extension points + +-- TODO + +-- ===================================================================== +-- Type families for the HsLit extension points + +-- We define a type family for each extension point. This is based on prepending +-- 'X' to the constructor name, for ease of reference. +type family XHsChar x +type family XHsCharPrim x +type family XHsString x +type family XHsStringPrim x +type family XHsInt x +type family XHsIntPrim x +type family XHsWordPrim x +type family XHsInt64Prim x +type family XHsWord64Prim x +type family XHsInteger x +type family XHsRat x +type family XHsFloatPrim x +type family XHsDoublePrim x +type family XXLit x + +-- ------------------------------------- +-- HsOverLit type families +type family XOverLit x +type family XXOverLit x + +-- ===================================================================== +-- Type families for the HsPat extension points + +type family XWildPat x +type family XVarPat x +type family XLazyPat x +type family XAsPat x +type family XParPat x +type family XBangPat x +type family XListPat x +type family XTuplePat x +type family XSumPat x +type family XConPat x +type family XViewPat x +type family XSplicePat x +type family XLitPat x +type family XNPat x +type family XNPlusKPat x +type family XSigPat x +type family XCoPat x +type family XXPat x + +-- ===================================================================== +-- Type families for the HsTypes type families + + +-- ------------------------------------- +-- LHsQTyVars type families +type family XHsQTvs x +type family XXLHsQTyVars x + +-- ------------------------------------- +-- HsOuterTyVarBndrs type families +type family XHsOuterImplicit x +type family XHsOuterExplicit x flag +type family XXHsOuterTyVarBndrs x + +-- ------------------------------------- +-- HsSigType type families +type family XHsSig x +type family XXHsSigType x + +-- ------------------------------------- +-- HsWildCardBndrs type families +type family XHsWC x b +type family XXHsWildCardBndrs x b + +-- ------------------------------------- +-- HsPatSigType type families +type family XHsPS x +type family XXHsPatSigType x + +-- ------------------------------------- +-- HsType type families +type family XForAllTy x +type family XQualTy x +type family XTyVar x +type family XAppTy x +type family XAppKindTy x +type family XFunTy x +type family XListTy x +type family XTupleTy x +type family XSumTy x +type family XOpTy x +type family XParTy x +type family XIParamTy x +type family XStarTy x +type family XKindSig x +type family XSpliceTy x +type family XDocTy x +type family XBangTy x +type family XRecTy x +type family XExplicitListTy x +type family XExplicitTupleTy x +type family XTyLit x +type family XWildCardTy x +type family XXType x + +-- --------------------------------------------------------------------- +-- HsForAllTelescope type families +type family XHsForAllVis x +type family XHsForAllInvis x +type family XXHsForAllTelescope x + +-- --------------------------------------------------------------------- +-- HsTyVarBndr type families +type family XUserTyVar x +type family XKindedTyVar x +type family XXTyVarBndr x + +-- --------------------------------------------------------------------- +-- ConDeclField type families +type family XConDeclField x +type family XXConDeclField x + +-- --------------------------------------------------------------------- +-- FieldOcc type families +type family XCFieldOcc x +type family XXFieldOcc x + +-- ===================================================================== +-- Type families for the HsImpExp type families + +-- ------------------------------------- +-- ImportDecl type families +type family XCImportDecl x +type family XXImportDecl x + +-- ------------------------------------- +-- IE type families +type family XIEVar x +type family XIEThingAbs x +type family XIEThingAll x +type family XIEThingWith x +type family XIEModuleContents x +type family XIEGroup x +type family XIEDoc x +type family XIEDocNamed x +type family XXIE x + +-- ------------------------------------- + +-- ===================================================================== +-- Misc + +-- | See Note [NoGhcTc] in GHC.Hs.Extension. It has to be in this +-- module because it is used like an extension point (in the data definitions +-- of types that should be parameter-agnostic. +type family NoGhcTc (p :: Type) + +-- ===================================================================== +-- End of Type family definitions +-- ===================================================================== diff --git a/compiler/Language/Haskell/Syntax/Lit.hs b/compiler/Language/Haskell/Syntax/Lit.hs new file mode 100644 index 0000000000..c5dd7ec45b --- /dev/null +++ b/compiler/Language/Haskell/Syntax/Lit.hs @@ -0,0 +1,204 @@ +{-# LANGUAGE CPP #-} +{-# LANGUAGE ConstraintKinds #-} +{-# LANGUAGE DeriveDataTypeable #-} +{-# LANGUAGE FlexibleContexts #-} +{-# LANGUAGE FlexibleInstances #-} +{-# LANGUAGE TypeFamilies #-} +{-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow] + -- in module Language.Haskell.Syntax.Extension + +{- +(c) The University of Glasgow 2006 +(c) The GRASP/AQUA Project, Glasgow University, 1992-1998 + +-} + +-- See Note [Language.Haskell.Syntax.* Hierarchy] for why not GHC.Hs.* + +-- | Source-language literals +module Language.Haskell.Syntax.Lit where + +#include "HsVersions.h" + +import GHC.Prelude + +import {-# SOURCE #-} Language.Haskell.Syntax.Expr ( HsExpr ) +import GHC.Types.Basic (PprPrec(..), topPrec ) +import GHC.Types.SourceText +import GHC.Core.Type +import GHC.Utils.Outputable +import GHC.Utils.Panic +import GHC.Data.FastString +import Language.Haskell.Syntax.Extension + +import Data.ByteString (ByteString) +import Data.Data hiding ( Fixity ) + +{- +************************************************************************ +* * +\subsection[HsLit]{Literals} +* * +************************************************************************ +-} + +-- Note [Literal source text] in GHC.Types.Basic for SourceText fields in +-- the following +-- Note [Trees that grow] in Language.Haskell.Syntax.Extension for the Xxxxx fields in the following +-- | Haskell Literal +data HsLit x + = HsChar (XHsChar x) {- SourceText -} Char + -- ^ Character + | HsCharPrim (XHsCharPrim x) {- SourceText -} Char + -- ^ Unboxed character + | HsString (XHsString x) {- SourceText -} FastString + -- ^ String + | HsStringPrim (XHsStringPrim x) {- SourceText -} !ByteString + -- ^ Packed bytes + | HsInt (XHsInt x) IntegralLit + -- ^ Genuinely an Int; arises from + -- "GHC.Tc.Deriv.Generate", and from TRANSLATION + | HsIntPrim (XHsIntPrim x) {- SourceText -} Integer + -- ^ literal @Int#@ + | HsWordPrim (XHsWordPrim x) {- SourceText -} Integer + -- ^ literal @Word#@ + | HsInt64Prim (XHsInt64Prim x) {- SourceText -} Integer + -- ^ literal @Int64#@ + | HsWord64Prim (XHsWord64Prim x) {- SourceText -} Integer + -- ^ literal @Word64#@ + | HsInteger (XHsInteger x) {- SourceText -} Integer Type + -- ^ Genuinely an integer; arises only + -- from TRANSLATION (overloaded + -- literals are done with HsOverLit) + | HsRat (XHsRat x) FractionalLit Type + -- ^ Genuinely a rational; arises only from + -- TRANSLATION (overloaded literals are + -- done with HsOverLit) + | HsFloatPrim (XHsFloatPrim x) FractionalLit + -- ^ Unboxed Float + | HsDoublePrim (XHsDoublePrim x) FractionalLit + -- ^ Unboxed Double + + | XLit !(XXLit x) + +instance Eq (HsLit x) where + (HsChar _ x1) == (HsChar _ x2) = x1==x2 + (HsCharPrim _ x1) == (HsCharPrim _ x2) = x1==x2 + (HsString _ x1) == (HsString _ x2) = x1==x2 + (HsStringPrim _ x1) == (HsStringPrim _ x2) = x1==x2 + (HsInt _ x1) == (HsInt _ x2) = x1==x2 + (HsIntPrim _ x1) == (HsIntPrim _ x2) = x1==x2 + (HsWordPrim _ x1) == (HsWordPrim _ x2) = x1==x2 + (HsInt64Prim _ x1) == (HsInt64Prim _ x2) = x1==x2 + (HsWord64Prim _ x1) == (HsWord64Prim _ x2) = x1==x2 + (HsInteger _ x1 _) == (HsInteger _ x2 _) = x1==x2 + (HsRat _ x1 _) == (HsRat _ x2 _) = x1==x2 + (HsFloatPrim _ x1) == (HsFloatPrim _ x2) = x1==x2 + (HsDoublePrim _ x1) == (HsDoublePrim _ x2) = x1==x2 + _ == _ = False + +-- | Haskell Overloaded Literal +data HsOverLit p + = OverLit { + ol_ext :: (XOverLit p), + ol_val :: OverLitVal, + ol_witness :: HsExpr p} -- Note [Overloaded literal witnesses] + + | XOverLit + !(XXOverLit p) + +-- Note [Literal source text] in GHC.Types.Basic for SourceText fields in +-- the following +-- | Overloaded Literal Value +data OverLitVal + = HsIntegral !IntegralLit -- ^ Integer-looking literals; + | HsFractional !FractionalLit -- ^ Frac-looking literals + | HsIsString !SourceText !FastString -- ^ String-looking literals + deriving Data + +negateOverLitVal :: OverLitVal -> OverLitVal +negateOverLitVal (HsIntegral i) = HsIntegral (negateIntegralLit i) +negateOverLitVal (HsFractional f) = HsFractional (negateFractionalLit f) +negateOverLitVal _ = panic "negateOverLitVal: argument is not a number" + +{- +Note [Overloaded literal witnesses] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +*Before* type checking, the HsExpr in an HsOverLit is the +name of the coercion function, 'fromInteger' or 'fromRational'. +*After* type checking, it is a witness for the literal, such as + (fromInteger 3) or lit_78 +This witness should replace the literal. + +This dual role is unusual, because we're replacing 'fromInteger' with +a call to fromInteger. Reason: it allows commoning up of the fromInteger +calls, which wouldn't be possible if the desugarer made the application. + +The PostTcType in each branch records the type the overload literal is +found to have. +-} + +-- Comparison operations are needed when grouping literals +-- for compiling pattern-matching (module GHC.HsToCore.Match.Literal) +instance (Eq (XXOverLit p)) => Eq (HsOverLit p) where + (OverLit _ val1 _) == (OverLit _ val2 _) = val1 == val2 + (XOverLit val1) == (XOverLit val2) = val1 == val2 + _ == _ = panic "Eq HsOverLit" + +instance Eq OverLitVal where + (HsIntegral i1) == (HsIntegral i2) = i1 == i2 + (HsFractional f1) == (HsFractional f2) = f1 == f2 + (HsIsString _ s1) == (HsIsString _ s2) = s1 == s2 + _ == _ = False + +instance (Ord (XXOverLit p)) => Ord (HsOverLit p) where + compare (OverLit _ val1 _) (OverLit _ val2 _) = val1 `compare` val2 + compare (XOverLit val1) (XOverLit val2) = val1 `compare` val2 + compare _ _ = panic "Ord HsOverLit" + +instance Ord OverLitVal where + compare (HsIntegral i1) (HsIntegral i2) = i1 `compare` i2 + compare (HsIntegral _) (HsFractional _) = LT + compare (HsIntegral _) (HsIsString _ _) = LT + compare (HsFractional f1) (HsFractional f2) = f1 `compare` f2 + compare (HsFractional _) (HsIntegral _) = GT + compare (HsFractional _) (HsIsString _ _) = LT + compare (HsIsString _ s1) (HsIsString _ s2) = s1 `uniqCompareFS` s2 + compare (HsIsString _ _) (HsIntegral _) = GT + compare (HsIsString _ _) (HsFractional _) = GT + +instance Outputable OverLitVal where + ppr (HsIntegral i) = pprWithSourceText (il_text i) (integer (il_value i)) + ppr (HsFractional f) = ppr f + ppr (HsIsString st s) = pprWithSourceText st (pprHsString s) + +-- | @'hsLitNeedsParens' p l@ returns 'True' if a literal @l@ needs +-- to be parenthesized under precedence @p@. +hsLitNeedsParens :: PprPrec -> HsLit x -> Bool +hsLitNeedsParens p = go + where + go (HsChar {}) = False + go (HsCharPrim {}) = False + go (HsString {}) = False + go (HsStringPrim {}) = False + go (HsInt _ x) = p > topPrec && il_neg x + go (HsIntPrim _ x) = p > topPrec && x < 0 + go (HsWordPrim {}) = False + go (HsInt64Prim _ x) = p > topPrec && x < 0 + go (HsWord64Prim {}) = False + go (HsInteger _ x _) = p > topPrec && x < 0 + go (HsRat _ x _) = p > topPrec && fl_neg x + go (HsFloatPrim _ x) = p > topPrec && fl_neg x + go (HsDoublePrim _ x) = p > topPrec && fl_neg x + go (XLit _) = False + +-- | @'hsOverLitNeedsParens' p ol@ returns 'True' if an overloaded literal +-- @ol@ needs to be parenthesized under precedence @p@. +hsOverLitNeedsParens :: PprPrec -> HsOverLit x -> Bool +hsOverLitNeedsParens p (OverLit { ol_val = olv }) = go olv + where + go :: OverLitVal -> Bool + go (HsIntegral x) = p > topPrec && il_neg x + go (HsFractional x) = p > topPrec && fl_neg x + go (HsIsString {}) = False +hsOverLitNeedsParens _ (XOverLit { }) = False diff --git a/compiler/Language/Haskell/Syntax/Pat.hs b/compiler/Language/Haskell/Syntax/Pat.hs new file mode 100644 index 0000000000..8de0cc96d3 --- /dev/null +++ b/compiler/Language/Haskell/Syntax/Pat.hs @@ -0,0 +1,374 @@ + +{-# LANGUAGE CPP #-} +{-# LANGUAGE ConstraintKinds #-} +{-# LANGUAGE DeriveDataTypeable #-} +{-# LANGUAGE DeriveTraversable #-} +{-# LANGUAGE FlexibleContexts #-} +{-# LANGUAGE FlexibleInstances #-} +{-# LANGUAGE LambdaCase #-} +{-# LANGUAGE ScopedTypeVariables #-} +{-# LANGUAGE TypeApplications #-} +{-# LANGUAGE TypeFamilies #-} +{-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow] + -- in module Language.Haskell.Syntax.Extension +{-# LANGUAGE ViewPatterns #-} +{- +(c) The University of Glasgow 2006 +(c) The GRASP/AQUA Project, Glasgow University, 1992-1998 + +\section[PatSyntax]{Abstract Haskell syntax---patterns} +-} + +-- See Note [Language.Haskell.Syntax.* Hierarchy] for why not GHC.Hs.* +module Language.Haskell.Syntax.Pat ( + Pat(..), LPat, + ConLikeP, + + HsConPatDetails, hsConPatArgs, + HsRecFields(..), HsRecField'(..), LHsRecField', + HsRecField, LHsRecField, + HsRecUpdField, LHsRecUpdField, + hsRecFields, hsRecFieldSel, hsRecFieldsArgs, + ) where + +import GHC.Prelude + +import {-# SOURCE #-} Language.Haskell.Syntax.Expr (SyntaxExpr, LHsExpr, HsSplice) + +-- friends: +import Language.Haskell.Syntax.Lit +import Language.Haskell.Syntax.Extension +import Language.Haskell.Syntax.Type +import GHC.Types.Basic +-- others: +import GHC.Core.Ppr ( {- instance OutputableBndr TyVar -} ) +import GHC.Utils.Outputable +import GHC.Types.SrcLoc +-- libraries: +import Data.Data hiding (TyCon,Fixity) + +type LPat p = XRec p (Pat p) + +-- | Pattern +-- +-- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnBang' + +-- For details on above see note [Api annotations] in GHC.Parser.Annotation +data Pat p + = ------------ Simple patterns --------------- + WildPat (XWildPat p) -- ^ Wildcard Pattern + -- The sole reason for a type on a WildPat is to + -- support hsPatType :: Pat Id -> Type + + -- AZ:TODO above comment needs to be updated + | VarPat (XVarPat p) + (LIdP p) -- ^ Variable Pattern + + -- See Note [Located RdrNames] in GHC.Hs.Expr + | LazyPat (XLazyPat p) + (LPat p) -- ^ Lazy Pattern + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnTilde' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | AsPat (XAsPat p) + (LIdP p) (LPat p) -- ^ As pattern + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnAt' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | ParPat (XParPat p) + (LPat p) -- ^ Parenthesised pattern + -- See Note [Parens in HsSyn] in GHC.Hs.Expr + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @'('@, + -- 'GHC.Parser.Annotation.AnnClose' @')'@ + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | BangPat (XBangPat p) + (LPat p) -- ^ Bang pattern + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnBang' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + ------------ Lists, tuples, arrays --------------- + | ListPat (XListPat p) + [LPat p] + -- For OverloadedLists a Just (ty,fn) gives + -- overall type of the pattern, and the toList +-- function to convert the scrutinee to a list value + + -- ^ Syntactic List + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @'['@, + -- 'GHC.Parser.Annotation.AnnClose' @']'@ + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | TuplePat (XTuplePat p) + -- after typechecking, holds the types of the tuple components + [LPat p] -- Tuple sub-patterns + Boxity -- UnitPat is TuplePat [] + -- You might think that the post typechecking Type was redundant, + -- because we can get the pattern type by getting the types of the + -- sub-patterns. + -- But it's essential + -- data T a where + -- T1 :: Int -> T Int + -- f :: (T a, a) -> Int + -- f (T1 x, z) = z + -- When desugaring, we must generate + -- f = /\a. \v::a. case v of (t::T a, w::a) -> + -- case t of (T1 (x::Int)) -> + -- Note the (w::a), NOT (w::Int), because we have not yet + -- refined 'a' to Int. So we must know that the second component + -- of the tuple is of type 'a' not Int. See selectMatchVar + -- (June 14: I'm not sure this comment is right; the sub-patterns + -- will be wrapped in CoPats, no?) + -- ^ Tuple sub-patterns + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : + -- 'GHC.Parser.Annotation.AnnOpen' @'('@ or @'(#'@, + -- 'GHC.Parser.Annotation.AnnClose' @')'@ or @'#)'@ + + | SumPat (XSumPat p) -- after typechecker, types of the alternative + (LPat p) -- Sum sub-pattern + ConTag -- Alternative (one-based) + Arity -- Arity (INVARIANT: ≥ 2) + -- ^ Anonymous sum pattern + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : + -- 'GHC.Parser.Annotation.AnnOpen' @'(#'@, + -- 'GHC.Parser.Annotation.AnnClose' @'#)'@ + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + ------------ Constructor patterns --------------- + | ConPat { + pat_con_ext :: XConPat p, + pat_con :: XRec p (ConLikeP p), + pat_args :: HsConPatDetails p + } + -- ^ Constructor Pattern + + ------------ View patterns --------------- + -- | - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnRarrow' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | ViewPat (XViewPat p) -- The overall type of the pattern + -- (= the argument type of the view function) + -- for hsPatType. + (LHsExpr p) + (LPat p) + -- ^ View Pattern + + ------------ Pattern splices --------------- + -- | - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @'$('@ + -- 'GHC.Parser.Annotation.AnnClose' @')'@ + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | SplicePat (XSplicePat p) + (HsSplice p) -- ^ Splice Pattern (Includes quasi-quotes) + + ------------ Literal and n+k patterns --------------- + | LitPat (XLitPat p) + (HsLit p) -- ^ Literal Pattern + -- Used for *non-overloaded* literal patterns: + -- Int#, Char#, Int, Char, String, etc. + + | NPat -- Natural Pattern + -- Used for all overloaded literals, + -- including overloaded strings with -XOverloadedStrings + (XNPat p) -- Overall type of pattern. Might be + -- different than the literal's type + -- if (==) or negate changes the type + (XRec p (HsOverLit p)) -- ALWAYS positive + (Maybe (SyntaxExpr p)) -- Just (Name of 'negate') for + -- negative patterns, Nothing + -- otherwise + (SyntaxExpr p) -- Equality checker, of type t->t->Bool + + -- ^ Natural Pattern + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnVal' @'+'@ + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | NPlusKPat (XNPlusKPat p) -- Type of overall pattern + (LIdP p) -- n+k pattern + (XRec p (HsOverLit p)) -- It'll always be an HsIntegral + (HsOverLit p) -- See Note [NPlusK patterns] in GHC.Tc.Gen.Pat + -- NB: This could be (PostTc ...), but that induced a + -- a new hs-boot file. Not worth it. + + (SyntaxExpr p) -- (>=) function, of type t1->t2->Bool + (SyntaxExpr p) -- Name of '-' (see GHC.Rename.Env.lookupSyntax) + -- ^ n+k pattern + + ------------ Pattern type signatures --------------- + -- | - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnDcolon' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | SigPat (XSigPat p) -- After typechecker: Type + (LPat p) -- Pattern with a type signature + (HsPatSigType (NoGhcTc p)) -- Signature can bind both + -- kind and type vars + + -- ^ Pattern with a type signature + + -- | Trees that Grow extension point for new constructors + | XPat + !(XXPat p) + +type family ConLikeP x + + +-- --------------------------------------------------------------------- + + +-- | Haskell Constructor Pattern Details +type HsConPatDetails p = HsConDetails (HsPatSigType (NoGhcTc p)) (LPat p) (HsRecFields p (LPat p)) + +hsConPatArgs :: HsConPatDetails p -> [LPat p] +hsConPatArgs (PrefixCon _ ps) = ps +hsConPatArgs (RecCon fs) = map (hsRecFieldArg . unLoc) (rec_flds fs) +hsConPatArgs (InfixCon p1 p2) = [p1,p2] + +-- | Haskell Record Fields +-- +-- HsRecFields is used only for patterns and expressions (not data type +-- declarations) +data HsRecFields p arg -- A bunch of record fields + -- { x = 3, y = True } + -- Used for both expressions and patterns + = HsRecFields { rec_flds :: [LHsRecField p arg], + rec_dotdot :: Maybe (Located Int) } -- Note [DotDot fields] + deriving (Functor, Foldable, Traversable) + + +-- Note [DotDot fields] +-- ~~~~~~~~~~~~~~~~~~~~ +-- The rec_dotdot field means this: +-- Nothing => the normal case +-- Just n => the group uses ".." notation, +-- +-- In the latter case: +-- +-- *before* renamer: rec_flds are exactly the n user-written fields +-- +-- *after* renamer: rec_flds includes *all* fields, with +-- the first 'n' being the user-written ones +-- and the remainder being 'filled in' implicitly + +-- | Located Haskell Record Field +type LHsRecField' p arg = Located (HsRecField' p arg) + +-- | Located Haskell Record Field +type LHsRecField p arg = Located (HsRecField p arg) + +-- | Located Haskell Record Update Field +type LHsRecUpdField p = Located (HsRecUpdField p) + +-- | Haskell Record Field +type HsRecField p arg = HsRecField' (FieldOcc p) arg + +-- | Haskell Record Update Field +type HsRecUpdField p = HsRecField' (AmbiguousFieldOcc p) (LHsExpr p) + +-- | Haskell Record Field +-- +-- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnEqual', +-- +-- For details on above see note [Api annotations] in GHC.Parser.Annotation +data HsRecField' id arg = HsRecField { + hsRecFieldLbl :: Located id, + hsRecFieldArg :: arg, -- ^ Filled in by renamer when punning + hsRecPun :: Bool -- ^ Note [Punning] + } deriving (Data, Functor, Foldable, Traversable) + + +-- Note [Punning] +-- ~~~~~~~~~~~~~~ +-- If you write T { x, y = v+1 }, the HsRecFields will be +-- HsRecField x x True ... +-- HsRecField y (v+1) False ... +-- That is, for "punned" field x is expanded (in the renamer) +-- to x=x; but with a punning flag so we can detect it later +-- (e.g. when pretty printing) +-- +-- If the original field was qualified, we un-qualify it, thus +-- T { A.x } means T { A.x = x } + + +-- Note [HsRecField and HsRecUpdField] +-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +-- A HsRecField (used for record construction and pattern matching) +-- contains an unambiguous occurrence of a field (i.e. a FieldOcc). +-- We can't just store the Name, because thanks to +-- DuplicateRecordFields this may not correspond to the label the user +-- wrote. +-- +-- A HsRecUpdField (used for record update) contains a potentially +-- ambiguous occurrence of a field (an AmbiguousFieldOcc). The +-- renamer will fill in the selector function if it can, but if the +-- selector is ambiguous the renamer will defer to the typechecker. +-- After the typechecker, a unique selector will have been determined. +-- +-- The renamer produces an Unambiguous result if it can, rather than +-- just doing the lookup in the typechecker, so that completely +-- unambiguous updates can be represented by 'GHC.HsToCore.Quote.repUpdFields'. +-- +-- For example, suppose we have: +-- +-- data S = MkS { x :: Int } +-- data T = MkT { x :: Int } +-- +-- f z = (z { x = 3 }) :: S +-- +-- The parsed HsRecUpdField corresponding to the record update will have: +-- +-- hsRecFieldLbl = Unambiguous "x" noExtField :: AmbiguousFieldOcc RdrName +-- +-- After the renamer, this will become: +-- +-- hsRecFieldLbl = Ambiguous "x" noExtField :: AmbiguousFieldOcc Name +-- +-- (note that the Unambiguous constructor is not type-correct here). +-- The typechecker will determine the particular selector: +-- +-- hsRecFieldLbl = Unambiguous "x" $sel:x:MkS :: AmbiguousFieldOcc Id +-- +-- See also Note [Disambiguating record fields] in GHC.Tc.Gen.Head. + +hsRecFields :: HsRecFields p arg -> [XCFieldOcc p] +hsRecFields rbinds = map (unLoc . hsRecFieldSel . unLoc) (rec_flds rbinds) + +-- Probably won't typecheck at once, things have changed :/ +hsRecFieldsArgs :: HsRecFields p arg -> [arg] +hsRecFieldsArgs rbinds = map (hsRecFieldArg . unLoc) (rec_flds rbinds) + +hsRecFieldSel :: HsRecField pass arg -> Located (XCFieldOcc pass) +hsRecFieldSel = fmap extFieldOcc . hsRecFieldLbl + + +{- +************************************************************************ +* * +* Printing patterns +* * +************************************************************************ +-} + +instance (Outputable arg) + => Outputable (HsRecFields p arg) where + ppr (HsRecFields { rec_flds = flds, rec_dotdot = Nothing }) + = braces (fsep (punctuate comma (map ppr flds))) + ppr (HsRecFields { rec_flds = flds, rec_dotdot = Just (unLoc -> n) }) + = braces (fsep (punctuate comma (map ppr (take n flds) ++ [dotdot]))) + where + dotdot = text ".." <+> whenPprDebug (ppr (drop n flds)) + +instance (Outputable p, Outputable arg) + => Outputable (HsRecField' p arg) where + ppr (HsRecField { hsRecFieldLbl = f, hsRecFieldArg = arg, + hsRecPun = pun }) + = ppr f <+> (ppUnless pun $ equals <+> ppr arg) diff --git a/compiler/Language/Haskell/Syntax/Pat.hs-boot b/compiler/Language/Haskell/Syntax/Pat.hs-boot new file mode 100644 index 0000000000..4ff0371e39 --- /dev/null +++ b/compiler/Language/Haskell/Syntax/Pat.hs-boot @@ -0,0 +1,13 @@ +{-# LANGUAGE KindSignatures #-} +{-# LANGUAGE RoleAnnotations #-} +{-# LANGUAGE TypeFamilies #-} + +-- See Note [Language.Haskell.Syntax.* Hierarchy] for why not GHC.Hs.* +module Language.Haskell.Syntax.Pat where + +import Language.Haskell.Syntax.Extension ( XRec ) +import Data.Kind + +type role Pat nominal +data Pat (i :: Type) +type LPat i = XRec i (Pat i) diff --git a/compiler/Language/Haskell/Syntax/Type.hs b/compiler/Language/Haskell/Syntax/Type.hs new file mode 100644 index 0000000000..6b0d61d025 --- /dev/null +++ b/compiler/Language/Haskell/Syntax/Type.hs @@ -0,0 +1,1304 @@ +{-# LANGUAGE CPP #-} +{-# LANGUAGE ConstraintKinds #-} +{-# LANGUAGE DeriveDataTypeable #-} +{-# LANGUAGE FlexibleContexts #-} +{-# LANGUAGE FlexibleInstances #-} +{-# LANGUAGE ScopedTypeVariables #-} +{-# LANGUAGE StandaloneDeriving #-} +{-# LANGUAGE TypeApplications #-} +{-# LANGUAGE TypeFamilies #-} +{-# LANGUAGE ViewPatterns #-} +{-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow] + -- in module Language.Haskell.Syntax.Extension +{- +(c) The University of Glasgow 2006 +(c) The GRASP/AQUA Project, Glasgow University, 1992-1998 + + +GHC.Hs.Type: Abstract syntax: user-defined types +-} + +-- See Note [Language.Haskell.Syntax.* Hierarchy] for why not GHC.Hs.* +module Language.Haskell.Syntax.Type ( + Mult, HsScaled(..), + hsMult, hsScaledThing, + HsArrow(..), + hsLinear, hsUnrestricted, + + HsType(..), HsCoreTy, LHsType, HsKind, LHsKind, + HsForAllTelescope(..), HsTyVarBndr(..), LHsTyVarBndr, + LHsQTyVars(..), + HsOuterTyVarBndrs(..), HsOuterFamEqnTyVarBndrs, HsOuterSigTyVarBndrs, + HsWildCardBndrs(..), + HsPatSigType(..), HsPSRn(..), + HsSigType(..), LHsSigType, LHsSigWcType, LHsWcType, + HsTupleSort(..), + HsContext, LHsContext, + HsTyLit(..), + HsIPName(..), hsIPNameFS, + HsArg(..), numVisibleArgs, + LHsTypeArg, + + LBangType, BangType, + HsSrcBang(..), HsImplBang(..), + SrcStrictness(..), SrcUnpackedness(..), + + ConDeclField(..), LConDeclField, + + HsConDetails(..), noTypeArgs, + + FieldOcc(..), LFieldOcc, + AmbiguousFieldOcc(..), + + mapHsOuterImplicit, + hsQTvExplicit, + isHsKindedTyVar, + hsPatSigType, + ) where + +#include "HsVersions.h" + +import GHC.Prelude + +import {-# SOURCE #-} Language.Haskell.Syntax.Expr ( HsSplice ) + +import Language.Haskell.Syntax.Extension + +import GHC.Types.SourceText +import GHC.Types.Name( Name ) +import GHC.Types.Name.Reader ( RdrName ) +import GHC.Core.DataCon( HsSrcBang(..), HsImplBang(..), + SrcStrictness(..), SrcUnpackedness(..) ) +import GHC.Core.Type +import GHC.Hs.Doc +import GHC.Types.Basic +import GHC.Types.SrcLoc +import GHC.Utils.Outputable +import GHC.Data.FastString +import GHC.Utils.Misc ( count ) +import GHC.Parser.Annotation + +import Data.Data hiding ( Fixity, Prefix, Infix ) +import Data.Void + +{- +************************************************************************ +* * +\subsection{Bang annotations} +* * +************************************************************************ +-} + +-- | Located Bang Type +type LBangType pass = XRec pass (BangType pass) + +-- | Bang Type +-- +-- In the parser, strictness and packedness annotations bind more tightly +-- than docstrings. This means that when consuming a 'BangType' (and looking +-- for 'HsBangTy') we must be ready to peer behind a potential layer of +-- 'HsDocTy'. See #15206 for motivation and 'getBangType' for an example. +type BangType pass = HsType pass -- Bangs are in the HsType data type + +{- +************************************************************************ +* * +\subsection{Data types} +* * +************************************************************************ + +This is the syntax for types as seen in type signatures. + +Note [HsBSig binder lists] +~~~~~~~~~~~~~~~~~~~~~~~~~~ +Consider a binder (or pattern) decorated with a type or kind, + \ (x :: a -> a). blah + forall (a :: k -> *) (b :: k). blah +Then we use a LHsBndrSig on the binder, so that the +renamer can decorate it with the variables bound +by the pattern ('a' in the first example, 'k' in the second), +assuming that neither of them is in scope already +See also Note [Kind and type-variable binders] in GHC.Rename.HsType + +Note [HsType binders] +~~~~~~~~~~~~~~~~~~~~~ +The system for recording type and kind-variable binders in HsTypes +is a bit complicated. Here's how it works. + +* In a HsType, + HsForAllTy represents an /explicit, user-written/ 'forall' that + is nested within another HsType + e.g. forall a b. {...} or + forall a b -> {...} + + Note that top-level 'forall's are represented with a + different AST form. See the description of HsOuterTyVarBndrs + below. + HsQualTy represents an /explicit, user-written/ context + e.g. (Eq a, Show a) => ... + The context can be empty if that's what the user wrote + These constructors represent what the user wrote, no more + and no less. + +* The ForAllTelescope field of HsForAllTy represents whether a forall is + invisible (e.g., forall a b. {...}, with a dot) or visible + (e.g., forall a b -> {...}, with an arrow). + +* HsTyVarBndr describes a quantified type variable written by the + user. For example + f :: forall a (b :: *). blah + here 'a' and '(b::*)' are each a HsTyVarBndr. A HsForAllTy has + a list of LHsTyVarBndrs. + +* HsOuterTyVarBndrs is used to represent the outermost quantified type + variables in a type that obeys the forall-or-nothing rule. An + HsOuterTyVarBndrs can be one of the following: + + HsOuterImplicit (implicit quantification, added by renamer) + f :: a -> a -- Desugars to f :: forall {a}. a -> a + HsOuterExplicit (explicit user quantifiation): + f :: forall a. a -> a + + See Note [forall-or-nothing rule]. + +* An HsSigType is an LHsType with an accompanying HsOuterTyVarBndrs that + represents the presence (or absence) of its outermost 'forall'. + See Note [Representing type signatures]. + +* HsWildCardBndrs is a wrapper that binds the wildcard variables + of the wrapped thing. It is filled in by the renamer + f :: _a -> _ + The enclosing HsWildCardBndrs binds the wildcards _a and _. + +* HsSigPatType describes types that appear in pattern signatures and + the signatures of term-level binders in RULES. Like + HsWildCardBndrs/HsOuterTyVarBndrs, they track the names of wildcard + variables and implicitly bound type variables. Unlike + HsOuterTyVarBndrs, however, HsSigPatTypes do not obey the + forall-or-nothing rule. See Note [Pattern signature binders and scoping]. + +* The explicit presence of these wrappers specifies, in the HsSyn, + exactly where implicit quantification is allowed, and where + wildcards are allowed. + +* LHsQTyVars is used in data/class declarations, where the user gives + explicit *type* variable bindings, but we need to implicitly bind + *kind* variables. For example + class C (a :: k -> *) where ... + The 'k' is implicitly bound in the hsq_tvs field of LHsQTyVars + +Note [The wildcard story for types] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Types can have wildcards in them, to support partial type signatures, +like f :: Int -> (_ , _a) -> _a + +A wildcard in a type can be + + * An anonymous wildcard, + written '_' + In HsType this is represented by HsWildCardTy. + The renamer leaves it untouched, and it is later given a fresh + meta tyvar in the typechecker. + + * A named wildcard, + written '_a', '_foo', etc + In HsType this is represented by (HsTyVar "_a") + i.e. a perfectly ordinary type variable that happens + to start with an underscore + +Note carefully: + +* When NamedWildCards is off, type variables that start with an + underscore really /are/ ordinary type variables. And indeed, even + when NamedWildCards is on you can bind _a explicitly as an ordinary + type variable: + data T _a _b = MkT _b _a + Or even: + f :: forall _a. _a -> _b + Here _a is an ordinary forall'd binder, but (With NamedWildCards) + _b is a named wildcard. (See the comments in #10982) + +* Named wildcards are bound by the HsWildCardBndrs (for types that obey the + forall-or-nothing rule) and HsPatSigType (for type signatures in patterns + and term-level binders in RULES), which wrap types that are allowed to have + wildcards. Unnamed wildcards, however are left unchanged until typechecking, + where we give them fresh wild tyvars and determine whether or not to emit + hole constraints on each wildcard (we don't if it's a visible type/kind + argument or a type family pattern). See related notes + Note [Wildcards in visible kind application] and + Note [Wildcards in visible type application] in GHC.Tc.Gen.HsType. + +* After type checking is done, we report what types the wildcards + got unified with. + +Note [Ordering of implicit variables] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Since the advent of -XTypeApplications, GHC makes promises about the ordering +of implicit variable quantification. Specifically, we offer that implicitly +quantified variables (such as those in const :: a -> b -> a, without a `forall`) +will occur in left-to-right order of first occurrence. Here are a few examples: + + const :: a -> b -> a -- forall a b. ... + f :: Eq a => b -> a -> a -- forall a b. ... contexts are included + + type a <-< b = b -> a + g :: a <-< b -- forall a b. ... type synonyms matter + + class Functor f where + fmap :: (a -> b) -> f a -> f b -- forall f a b. ... + -- The f is quantified by the class, so only a and b are considered in fmap + +This simple story is complicated by the possibility of dependency: all variables +must come after any variables mentioned in their kinds. + + typeRep :: Typeable a => TypeRep (a :: k) -- forall k a. ... + +The k comes first because a depends on k, even though the k appears later than +the a in the code. Thus, GHC does a *stable topological sort* on the variables. +By "stable", we mean that any two variables who do not depend on each other +preserve their existing left-to-right ordering. + +Implicitly bound variables are collected by the extract- family of functions +(extractHsTysRdrTyVars, extractHsTyVarBndrsKVs, etc.) in GHC.Rename.HsType. +These functions thus promise to keep left-to-right ordering. +Look for pointers to this note to see the places where the action happens. + +Note that we also maintain this ordering in kind signatures. Even though +there's no visible kind application (yet), having implicit variables be +quantified in left-to-right order in kind signatures is nice since: + +* It's consistent with the treatment for type signatures. +* It can affect how types are displayed with -fprint-explicit-kinds (see + #15568 for an example), which is a situation where knowing the order in + which implicit variables are quantified can be useful. +* In the event that visible kind application is implemented, the order in + which we would expect implicit variables to be ordered in kinds will have + already been established. +-} + +-- | Located Haskell Context +type LHsContext pass = XRec pass (HsContext pass) + -- ^ 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnUnit' + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + +-- | Haskell Context +type HsContext pass = [LHsType pass] + +-- | Located Haskell Type +type LHsType pass = XRec pass (HsType pass) + -- ^ May have 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnComma' when + -- in a list + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + +-- | Haskell Kind +type HsKind pass = HsType pass + +-- | Located Haskell Kind +type LHsKind pass = XRec pass (HsKind pass) + -- ^ 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnDcolon' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + +-------------------------------------------------- +-- LHsQTyVars +-- The explicitly-quantified binders in a data/type declaration + +-- | The type variable binders in an 'HsForAllTy'. +-- See also @Note [Variable Specificity and Forall Visibility]@ in +-- "GHC.Tc.Gen.HsType". +data HsForAllTelescope pass + = HsForAllVis -- ^ A visible @forall@ (e.g., @forall a -> {...}@). + -- These do not have any notion of specificity, so we use + -- '()' as a placeholder value. + { hsf_xvis :: XHsForAllVis pass + , hsf_vis_bndrs :: [LHsTyVarBndr () pass] + } + | HsForAllInvis -- ^ An invisible @forall@ (e.g., @forall a {b} c. {...}@), + -- where each binder has a 'Specificity'. + { hsf_xinvis :: XHsForAllInvis pass + , hsf_invis_bndrs :: [LHsTyVarBndr Specificity pass] + } + | XHsForAllTelescope !(XXHsForAllTelescope pass) + +-- | Located Haskell Type Variable Binder +type LHsTyVarBndr flag pass = XRec pass (HsTyVarBndr flag pass) + -- See Note [HsType binders] + +-- | Located Haskell Quantified Type Variables +data LHsQTyVars pass -- See Note [HsType binders] + = HsQTvs { hsq_ext :: XHsQTvs pass + + , hsq_explicit :: [LHsTyVarBndr () pass] + -- Explicit variables, written by the user + } + | XLHsQTyVars !(XXLHsQTyVars pass) + +hsQTvExplicit :: LHsQTyVars pass -> [LHsTyVarBndr () pass] +hsQTvExplicit = hsq_explicit + +------------------------------------------------ +-- HsOuterTyVarBndrs +-- Used to quantify the outermost type variable binders of a type that obeys +-- the forall-or-nothing rule. These are used to represent the outermost +-- quantification in: +-- * Type signatures (LHsSigType/LHsSigWcType) +-- * Patterns in a type/data family instance (HsTyPats) +-- +-- We support two forms: +-- HsOuterImplicit (implicit quantification, added by renamer) +-- f :: a -> a -- Desugars to f :: forall {a}. a -> a +-- type instance F (a,b) = a->b +-- HsOuterExplicit (explicit user quantifiation): +-- f :: forall a. a -> a +-- type instance forall a b. F (a,b) = a->b +-- +-- In constrast, when the user writes /visible/ quanitification +-- T :: forall k -> k -> Type +-- we use use HsOuterImplicit, wrapped around a HsForAllTy +-- for the visible quantification +-- +-- See Note [forall-or-nothing rule] + +-- | The outermost type variables in a type that obeys the @forall@-or-nothing +-- rule. See @Note [forall-or-nothing rule]@. +data HsOuterTyVarBndrs flag pass + = HsOuterImplicit -- ^ Implicit forall, e.g., + -- @f :: a -> b -> b@ + { hso_ximplicit :: XHsOuterImplicit pass + } + | HsOuterExplicit -- ^ Explicit forall, e.g., + -- @f :: forall a b. a -> b -> b@ + { hso_xexplicit :: XHsOuterExplicit pass flag + , hso_bndrs :: [LHsTyVarBndr flag (NoGhcTc pass)] + } + | XHsOuterTyVarBndrs !(XXHsOuterTyVarBndrs pass) + +-- | Used for signatures, e.g., +-- +-- @ +-- f :: forall a {b}. blah +-- @ +-- +-- We use 'Specificity' for the 'HsOuterTyVarBndrs' @flag@ to allow +-- distinguishing between specified and inferred type variables. +type HsOuterSigTyVarBndrs = HsOuterTyVarBndrs Specificity + +-- | Used for type-family instance equations, e.g., +-- +-- @ +-- type instance forall a. F [a] = Tree a +-- @ +-- +-- The notion of specificity is irrelevant in type family equations, so we use +-- @()@ for the 'HsOuterTyVarBndrs' @flag@. +type HsOuterFamEqnTyVarBndrs = HsOuterTyVarBndrs () + +-- | Haskell Wildcard Binders +data HsWildCardBndrs pass thing + -- See Note [HsType binders] + -- See Note [The wildcard story for types] + = HsWC { hswc_ext :: XHsWC pass thing + -- after the renamer + -- Wild cards, only named + -- See Note [Wildcards in visible kind application] + + , hswc_body :: thing + -- Main payload (type or list of types) + -- If there is an extra-constraints wildcard, + -- it's still there in the hsc_body. + } + | XHsWildCardBndrs !(XXHsWildCardBndrs pass thing) + +-- | Types that can appear in pattern signatures, as well as the signatures for +-- term-level binders in RULES. +-- See @Note [Pattern signature binders and scoping]@. +-- +-- This is very similar to 'HsSigWcType', but with +-- slightly different semantics: see @Note [HsType binders]@. +-- See also @Note [The wildcard story for types]@. +data HsPatSigType pass + = HsPS { hsps_ext :: XHsPS pass -- ^ After renamer: 'HsPSRn' + , hsps_body :: LHsType pass -- ^ Main payload (the type itself) + } + | XHsPatSigType !(XXHsPatSigType pass) + +-- | The extension field for 'HsPatSigType', which is only used in the +-- renamer onwards. See @Note [Pattern signature binders and scoping]@. +data HsPSRn = HsPSRn + { hsps_nwcs :: [Name] -- ^ Wildcard names + , hsps_imp_tvs :: [Name] -- ^ Implicitly bound variable names + } + deriving Data + +-- | Located Haskell Signature Type +type LHsSigType pass = Located (HsSigType pass) -- Implicit only + +-- | Located Haskell Wildcard Type +type LHsWcType pass = HsWildCardBndrs pass (LHsType pass) -- Wildcard only + +-- | Located Haskell Signature Wildcard Type +type LHsSigWcType pass = HsWildCardBndrs pass (LHsSigType pass) -- Both + +-- | A type signature that obeys the @forall@-or-nothing rule. In other +-- words, an 'LHsType' that uses an 'HsOuterSigTyVarBndrs' to represent its +-- outermost type variable quantification. +-- See @Note [Representing type signatures]@. +data HsSigType pass + = HsSig { sig_ext :: XHsSig pass + , sig_bndrs :: HsOuterSigTyVarBndrs pass + , sig_body :: LHsType pass + } + | XHsSigType !(XXHsSigType pass) + +hsPatSigType :: HsPatSigType pass -> LHsType pass +hsPatSigType = hsps_body + +{- +Note [forall-or-nothing rule] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Free variables in signatures are usually bound in an implicit 'forall' at the +beginning of user-written signatures. However, if the signature has an +explicit, invisible forall at the beginning, this is disabled. This is referred +to as the forall-or-nothing rule. + +The idea is nested foralls express something which is only expressible +explicitly, while a top level forall could (usually) be replaced with an +implicit binding. Top-level foralls alone ("forall.") are therefore an +indication that the user is trying to be fastidious, so we don't implicitly +bind any variables. + +Note that this rule only applies to outermost /in/visible 'forall's, and not +outermost visible 'forall's. See #18660 for more on this point. + +Here are some concrete examples to demonstrate the forall-or-nothing rule in +action: + + type F1 :: a -> b -> b -- Legal; a,b are implicitly quantified. + -- Equivalently: forall a b. a -> b -> b + + type F2 :: forall a b. a -> b -> b -- Legal; explicitly quantified + + type F3 :: forall a. a -> b -> b -- Illegal; the forall-or-nothing rule says that + -- if you quantify a, you must also quantify b + + type F4 :: forall a -> b -> b -- Legal; the top quantifier (forall a) is a /visible/ + -- quantifer, so the "nothing" part of the forall-or-nothing + -- rule applies, and b is therefore implicitly quantified. + -- Equivalently: forall b. forall a -> b -> b + + type F5 :: forall b. forall a -> b -> c -- Illegal; the forall-or-nothing rule says that + -- if you quantify b, you must also quantify c + + type F6 :: forall a -> forall b. b -> c -- Legal: just like F4. + +For a complete list of all places where the forall-or-nothing rule applies, see +"The `forall`-or-nothing rule" section of the GHC User's Guide. + +Any type that obeys the forall-or-nothing rule is represented in the AST with +an HsOuterTyVarBndrs: + +* If the type has an outermost, invisible 'forall', it uses HsOuterExplicit, + which contains a list of the explicitly quantified type variable binders in + `hso_bndrs`. After typechecking, HsOuterExplicit also stores a list of the + explicitly quantified `InvisTVBinder`s in + `hso_xexplicit :: XHsOuterExplicit GhcTc`. + +* Otherwise, it uses HsOuterImplicit. HsOuterImplicit is used for different + things depending on the phase: + + * After parsing, it does not store anything in particular. + * After renaming, it stores the implicitly bound type variable `Name`s in + `hso_ximplicit :: XHsOuterImplicit GhcRn`. + * After typechecking, it stores the implicitly bound `TyVar`s in + `hso_ximplicit :: XHsOuterImplicit GhcTc`. + + NB: this implicit quantification is purely lexical: we bind any + type or kind variables that are not in scope. The type checker + may subsequently quantify over further kind variables. + See Note [Binding scoped type variables] in GHC.Tc.Gen.Sig. + +HsOuterTyVarBndrs GhcTc is used in the typechecker as an intermediate data type +for storing the outermost TyVars/InvisTVBinders in a type. +See GHC.Tc.Gen.HsType.bindOuterTKBndrsX for an example of this. + +Note [Representing type signatures] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +HsSigType is used to represent an explicit user type signature. These are +used in a variety of places. Some examples include: + +* Type signatures (e.g., f :: a -> a) +* Standalone kind signatures (e.g., type G :: a -> a) +* GADT constructor types (e.g., data T where MkT :: a -> T) + +A HsSigType is the combination of an HsOuterSigTyVarBndrs and an LHsType: + +* The HsOuterSigTyVarBndrs binds the /explicitly/ quantified type variables + when the type signature has an outermost, user-written 'forall' (i.e, + the HsOuterExplicit constructor is used). If there is no outermost 'forall', + then it binds the /implicitly/ quantified type variables instead (i.e., + the HsOuterImplicit constructor is used). +* The LHsType represents the rest of the type. + +E.g. For a signature like + f :: forall k (a::k). blah +we get + HsSig { sig_bndrs = HsOuterExplicit { hso_bndrs = [k, (a :: k)] } + , sig_body = blah } + +Note [Pattern signature binders and scoping] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Consider the pattern signatures like those on `t` and `g` in: + + f = let h = \(t :: (b, b) -> + \(g :: forall a. a -> b) -> + ...(t :: (Int,Int))... + in woggle + +* The `b` in t's pattern signature is implicitly bound and scopes over + the signature and the body of the lambda. It stands for a type (any type); + indeed we subsequently discover that b=Int. + (See Note [TyVarTv] in GHC.Tc.Utils.TcMType for more on this point.) +* The `b` in g's pattern signature is an /occurrence/ of the `b` bound by + t's pattern signature. +* The `a` in `forall a` scopes only over the type `a -> b`, not over the body + of the lambda. +* There is no forall-or-nothing rule for pattern signatures, which is why the + type `forall a. a -> b` is permitted in `g`'s pattern signature, even though + `b` is not explicitly bound. See Note [forall-or-nothing rule]. + +Similar scoping rules apply to term variable binders in RULES, like in the +following example: + + {-# RULES "h" forall (t :: (b, b)) (g :: forall a. a -> b). h t g = ... #-} + +Just like in pattern signatures, the `b` in t's signature is implicitly bound +and scopes over the remainder of the RULE. As a result, the `b` in g's +signature is an occurrence. Moreover, the `a` in `forall a` scopes only over +the type `a -> b`, and the forall-or-nothing rule does not apply. + +While quite similar, RULE term binder signatures behave slightly differently +from pattern signatures in two ways: + +1. Unlike in pattern signatures, where type variables can stand for any type, + type variables in RULE term binder signatures are skolems. + See Note [Typechecking pattern signature binders] in GHC.Tc.Gen.HsType for + more on this point. + + In this sense, type variables in pattern signatures are quite similar to + named wildcards, as both can refer to arbitrary types. The main difference + lies in error reporting: if a named wildcard `_a` in a pattern signature + stands for Int, then by default GHC will emit a warning stating as much. + Changing `_a` to `a`, on the other hand, will cause it not to be reported. +2. In the `h` RULE above, only term variables are explicitly bound, so any free + type variables in the term variables' signatures are implicitly bound. + This is just like how the free type variables in pattern signatures are + implicitly bound. If a RULE explicitly binds both term and type variables, + however, then free type variables in term signatures are /not/ implicitly + bound. For example, this RULE would be ill scoped: + + {-# RULES "h2" forall b. forall (t :: (b, c)) (g :: forall a. a -> b). + h2 t g = ... #-} + + This is because `b` and `c` occur free in the signature for `t`, but only + `b` was explicitly bound, leaving `c` out of scope. If the RULE had started + with `forall b c.`, then it would have been accepted. + +The types in pattern signatures and RULE term binder signatures are represented +in the AST by HsSigPatType. From the renamer onward, the hsps_ext field (of +type HsPSRn) tracks the names of named wildcards and implicitly bound type +variables so that they can be brought into scope during renaming and +typechecking. + +Note [Lexically scoped type variables] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +The ScopedTypeVariables extension does two things: + +* It allows the use of type signatures in patterns + (e.g., `f (x :: a -> a) = ...`). See + Note [Pattern signature binders and scoping] for more on this point. +* It brings lexically scoped type variables into scope for certain type + signatures with outermost invisible 'forall's. + +This Note concerns the latter bullet point. Per the +"Lexically scoped type variables" section of the GHC User's Guide, the +following forms of type signatures can have lexically scoped type variables: + +* In declarations with type signatures, e.g., + + f :: forall a. a -> a + f x = e @a + + Here, the 'forall a' brings 'a' into scope over the body of 'f'. + + Note that ScopedTypeVariables does /not/ interact with standalone kind + signatures, only type signatures. + +* In explicit type annotations in expressions, e.g., + + id @a :: forall a. a -> a + +* In instance declarations, e.g., + + instance forall a. C [a] where + m = e @a + + Note that unlike the examples above, the use of an outermost 'forall' isn't + required to bring 'a' into scope. That is, the following would also work: + + instance forall a. C [a] where + m = e @a + +Note that all of the types above obey the forall-or-nothing rule. As a result, +the places in the AST that can have lexically scoped type variables are a +subset of the places that use HsOuterTyVarBndrs +(See Note [forall-or-nothing rule].) + +Some other observations about lexically scoped type variables: + +* Only type variables bound by an /invisible/ forall can be lexically scoped. + See Note [hsScopedTvs and visible foralls]. +* The lexically scoped type variables may be a strict subset of the type + variables brought into scope by a type signature. + See Note [Binding scoped type variables] in GHC.Tc.Gen.Sig. +-} + +mapHsOuterImplicit :: (XHsOuterImplicit pass -> XHsOuterImplicit pass) + -> HsOuterTyVarBndrs flag pass + -> HsOuterTyVarBndrs flag pass +mapHsOuterImplicit f (HsOuterImplicit{hso_ximplicit = imp}) = + HsOuterImplicit{hso_ximplicit = f imp} +mapHsOuterImplicit _ hso@(HsOuterExplicit{}) = hso +mapHsOuterImplicit _ hso@(XHsOuterTyVarBndrs{}) = hso + + +-------------------------------------------------- +-- | These names are used early on to store the names of implicit +-- parameters. They completely disappear after type-checking. +newtype HsIPName = HsIPName FastString + deriving( Eq, Data ) + +hsIPNameFS :: HsIPName -> FastString +hsIPNameFS (HsIPName n) = n + +instance Outputable HsIPName where + ppr (HsIPName n) = char '?' <> ftext n -- Ordinary implicit parameters + +instance OutputableBndr HsIPName where + pprBndr _ n = ppr n -- Simple for now + pprInfixOcc n = ppr n + pprPrefixOcc n = ppr n + +-------------------------------------------------- + +-- | Haskell Type Variable Binder +-- The flag annotates the binder. It is 'Specificity' in places where +-- explicit specificity is allowed (e.g. x :: forall {a} b. ...) or +-- '()' in other places. +data HsTyVarBndr flag pass + = UserTyVar -- no explicit kinding + (XUserTyVar pass) + flag + (LIdP pass) + -- See Note [Located RdrNames] in GHC.Hs.Expr + + | KindedTyVar + (XKindedTyVar pass) + flag + (LIdP pass) + (LHsKind pass) -- The user-supplied kind signature + -- ^ + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen', + -- 'GHC.Parser.Annotation.AnnDcolon', 'GHC.Parser.Annotation.AnnClose' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | XTyVarBndr + !(XXTyVarBndr pass) + +-- | Does this 'HsTyVarBndr' come with an explicit kind annotation? +isHsKindedTyVar :: HsTyVarBndr flag pass -> Bool +isHsKindedTyVar (UserTyVar {}) = False +isHsKindedTyVar (KindedTyVar {}) = True +isHsKindedTyVar (XTyVarBndr {}) = False + +-- | Haskell Type +data HsType pass + = HsForAllTy -- See Note [HsType binders] + { hst_xforall :: XForAllTy pass + , hst_tele :: HsForAllTelescope pass + -- Explicit, user-supplied 'forall a {b} c' + , hst_body :: LHsType pass -- body type + } + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnForall', + -- 'GHC.Parser.Annotation.AnnDot','GHC.Parser.Annotation.AnnDarrow' + -- For details on above see note [Api annotations] in "GHC.Parser.Annotation" + + | HsQualTy -- See Note [HsType binders] + { hst_xqual :: XQualTy pass + , hst_ctxt :: LHsContext pass -- Context C => blah + , hst_body :: LHsType pass } + + | HsTyVar (XTyVar pass) + PromotionFlag -- Whether explicitly promoted, + -- for the pretty printer + (LIdP pass) + -- Type variable, type constructor, or data constructor + -- see Note [Promotions (HsTyVar)] + -- See Note [Located RdrNames] in GHC.Hs.Expr + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : None + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | HsAppTy (XAppTy pass) + (LHsType pass) + (LHsType pass) + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : None + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | HsAppKindTy (XAppKindTy pass) -- type level type app + (LHsType pass) + (LHsKind pass) + + | HsFunTy (XFunTy pass) + (HsArrow pass) + (LHsType pass) -- function type + (LHsType pass) + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnRarrow', + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | HsListTy (XListTy pass) + (LHsType pass) -- Element type + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @'['@, + -- 'GHC.Parser.Annotation.AnnClose' @']'@ + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | HsTupleTy (XTupleTy pass) + HsTupleSort + [LHsType pass] -- Element types (length gives arity) + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @'(' or '(#'@, + -- 'GHC.Parser.Annotation.AnnClose' @')' or '#)'@ + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | HsSumTy (XSumTy pass) + [LHsType pass] -- Element types (length gives arity) + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @'(#'@, + -- 'GHC.Parser.Annotation.AnnClose' '#)'@ + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | HsOpTy (XOpTy pass) + (LHsType pass) (LIdP pass) (LHsType pass) + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : None + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | HsParTy (XParTy pass) + (LHsType pass) -- See Note [Parens in HsSyn] in GHC.Hs.Expr + -- Parenthesis preserved for the precedence re-arrangement in + -- GHC.Rename.HsType + -- It's important that a * (b + c) doesn't get rearranged to (a*b) + c! + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @'('@, + -- 'GHC.Parser.Annotation.AnnClose' @')'@ + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | HsIParamTy (XIParamTy pass) + (XRec pass HsIPName) -- (?x :: ty) + (LHsType pass) -- Implicit parameters as they occur in + -- contexts + -- ^ + -- > (?x :: ty) + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnDcolon' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | HsStarTy (XStarTy pass) + Bool -- Is this the Unicode variant? + -- Note [HsStarTy] + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : None + + | HsKindSig (XKindSig pass) + (LHsType pass) -- (ty :: kind) + (LHsKind pass) -- A type with a kind signature + -- ^ + -- > (ty :: kind) + -- + -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @'('@, + -- 'GHC.Parser.Annotation.AnnDcolon','GHC.Parser.Annotation.AnnClose' @')'@ + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | HsSpliceTy (XSpliceTy pass) + (HsSplice pass) -- Includes quasi-quotes + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @'$('@, + -- 'GHC.Parser.Annotation.AnnClose' @')'@ + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | HsDocTy (XDocTy pass) + (LHsType pass) LHsDocString -- A documented type + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : None + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | HsBangTy (XBangTy pass) + HsSrcBang (LHsType pass) -- Bang-style type annotations + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : + -- 'GHC.Parser.Annotation.AnnOpen' @'{-\# UNPACK' or '{-\# NOUNPACK'@, + -- 'GHC.Parser.Annotation.AnnClose' @'#-}'@ + -- 'GHC.Parser.Annotation.AnnBang' @\'!\'@ + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | HsRecTy (XRecTy pass) + [LConDeclField pass] -- Only in data type declarations + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @'{'@, + -- 'GHC.Parser.Annotation.AnnClose' @'}'@ + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | HsExplicitListTy -- A promoted explicit list + (XExplicitListTy pass) + PromotionFlag -- whether explicitly promoted, for pretty printer + [LHsType pass] + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @"'["@, + -- 'GHC.Parser.Annotation.AnnClose' @']'@ + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | HsExplicitTupleTy -- A promoted explicit tuple + (XExplicitTupleTy pass) + [LHsType pass] + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @"'("@, + -- 'GHC.Parser.Annotation.AnnClose' @')'@ + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | HsTyLit (XTyLit pass) HsTyLit -- A promoted numeric literal. + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : None + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + | HsWildCardTy (XWildCardTy pass) -- A type wildcard + -- See Note [The wildcard story for types] + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : None + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + + -- For adding new constructors via Trees that Grow + | XHsType + (XXType pass) + +-- An escape hatch for tunnelling a Core 'Type' through 'HsType'. +-- For more details on how this works, see: +-- +-- * @Note [Renaming HsCoreTys]@ in "GHC.Rename.HsType" +-- +-- * @Note [Typechecking HsCoreTys]@ in "GHC.Tc.Gen.HsType" +type HsCoreTy = Type + + +-- Note [Literal source text] in GHC.Types.Basic for SourceText fields in +-- the following +-- | Haskell Type Literal +data HsTyLit + = HsNumTy SourceText Integer + | HsStrTy SourceText FastString + deriving Data + +-- | Denotes the type of arrows in the surface language +data HsArrow pass + = HsUnrestrictedArrow IsUnicodeSyntax + -- ^ a -> b or a → b + | HsLinearArrow IsUnicodeSyntax + -- ^ a %1 -> b or a %1 → b, or a ⊸ b + | HsExplicitMult IsUnicodeSyntax (LHsType pass) + -- ^ a %m -> b or a %m → b (very much including `a %Many -> b`! + -- This is how the programmer wrote it). It is stored as an + -- `HsType` so as to preserve the syntax as written in the + -- program. + +-- | This is used in the syntax. In constructor declaration. It must keep the +-- arrow representation. +data HsScaled pass a = HsScaled (HsArrow pass) a + +hsMult :: HsScaled pass a -> HsArrow pass +hsMult (HsScaled m _) = m + +hsScaledThing :: HsScaled pass a -> a +hsScaledThing (HsScaled _ t) = t + +-- | When creating syntax we use the shorthands. It's better for printing, also, +-- the shorthands work trivially at each pass. +hsUnrestricted, hsLinear :: a -> HsScaled pass a +hsUnrestricted = HsScaled (HsUnrestrictedArrow NormalSyntax) +hsLinear = HsScaled (HsLinearArrow NormalSyntax) + +instance Outputable a => Outputable (HsScaled pass a) where + ppr (HsScaled _cnt t) = -- ppr cnt <> ppr t + ppr t + +{- +Note [Unit tuples] +~~~~~~~~~~~~~~~~~~ +Consider the type + type instance F Int = () +We want to parse that "()" + as HsTupleTy HsBoxedOrConstraintTuple [], +NOT as HsTyVar unitTyCon + +Why? Because F might have kind (* -> Constraint), so we when parsing we +don't know if that tuple is going to be a constraint tuple or an ordinary +unit tuple. The HsTupleSort flag is specifically designed to deal with +that, but it has to work for unit tuples too. + +Note [Promotions (HsTyVar)] +~~~~~~~~~~~~~~~~~~~~~~~~~~~ +HsTyVar: A name in a type or kind. + Here are the allowed namespaces for the name. + In a type: + Var: not allowed + Data: promoted data constructor + Tv: type variable + TcCls before renamer: type constructor, class constructor, or promoted data constructor + TcCls after renamer: type constructor or class constructor + In a kind: + Var, Data: not allowed + Tv: kind variable + TcCls: kind constructor or promoted type constructor + + The 'Promoted' field in an HsTyVar captures whether the type was promoted in + the source code by prefixing an apostrophe. + +Note [HsStarTy] +~~~~~~~~~~~~~~~ +When the StarIsType extension is enabled, we want to treat '*' and its Unicode +variant identically to 'Data.Kind.Type'. Unfortunately, doing so in the parser +would mean that when we pretty-print it back, we don't know whether the user +wrote '*' or 'Type', and lose the parse/ppr roundtrip property. + +As a workaround, we parse '*' as HsStarTy (if it stands for 'Data.Kind.Type') +and then desugar it to 'Data.Kind.Type' in the typechecker (see tc_hs_type). +When '*' is a regular type operator (StarIsType is disabled), HsStarTy is not +involved. + + +Note [Promoted lists and tuples] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Notice the difference between + HsListTy HsExplicitListTy + HsTupleTy HsExplicitListTupleTy + +E.g. f :: [Int] HsListTy + + g3 :: T '[] All these use + g2 :: T '[True] HsExplicitListTy + g1 :: T '[True,False] + g1a :: T [True,False] (can omit ' where unambiguous) + + kind of T :: [Bool] -> * This kind uses HsListTy! + +E.g. h :: (Int,Bool) HsTupleTy; f is a pair + k :: S '(True,False) HsExplicitTypleTy; S is indexed by + a type-level pair of booleans + kind of S :: (Bool,Bool) -> * This kind uses HsExplicitTupleTy + +Note [Distinguishing tuple kinds] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Apart from promotion, tuples can have one of three different kinds: + + x :: (Int, Bool) -- Regular boxed tuples + f :: Int# -> (# Int#, Int# #) -- Unboxed tuples + g :: (Eq a, Ord a) => a -- Constraint tuples + +For convenience, internally we use a single constructor for all of these, +namely HsTupleTy, but keep track of the tuple kind (in the first argument to +HsTupleTy, a HsTupleSort). We can tell if a tuple is unboxed while parsing, +because of the #. However, with -XConstraintKinds we can only distinguish +between constraint and boxed tuples during type checking, in general. Hence the +two constructors of HsTupleSort: + + HsUnboxedTuple -> Produced by the parser + HsBoxedOrConstraintTuple -> Could be a boxed or a constraint + tuple. Produced by the parser only, + disappears after type checking + +After typechecking, we use TupleSort (which clearly distinguishes between +constraint tuples and boxed tuples) rather than HsTupleSort. +-} + +-- | Haskell Tuple Sort +data HsTupleSort = HsUnboxedTuple + | HsBoxedOrConstraintTuple + deriving Data + +-- | Located Constructor Declaration Field +type LConDeclField pass = XRec pass (ConDeclField pass) + -- ^ May have 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnComma' when + -- in a list + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + +-- | Constructor Declaration Field +data ConDeclField pass -- Record fields have Haddock docs on them + = ConDeclField { cd_fld_ext :: XConDeclField pass, + cd_fld_names :: [LFieldOcc pass], + -- ^ See Note [ConDeclField passs] + cd_fld_type :: LBangType pass, + cd_fld_doc :: Maybe LHsDocString } + -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnDcolon' + + -- For details on above see note [Api annotations] in GHC.Parser.Annotation + | XConDeclField !(XXConDeclField pass) + +-- | Describes the arguments to a data constructor. This is a common +-- representation for several constructor-related concepts, including: +-- +-- * The arguments in a Haskell98-style constructor declaration +-- (see 'HsConDeclH98Details' in "GHC.Hs.Decls"). +-- +-- * The arguments in constructor patterns in @case@/function definitions +-- (see 'HsConPatDetails' in "GHC.Hs.Pat"). +-- +-- * The left-hand side arguments in a pattern synonym binding +-- (see 'HsPatSynDetails' in "GHC.Hs.Binds"). +-- +-- One notable exception is the arguments in a GADT constructor, which uses +-- a separate data type entirely (see 'HsConDeclGADTDetails' in +-- "GHC.Hs.Decls"). This is because GADT constructors cannot be declared with +-- infix syntax, unlike the concepts above (#18844). +data HsConDetails tyarg arg rec + = PrefixCon [tyarg] [arg] -- C @t1 @t2 p1 p2 p3 + | RecCon rec -- C { x = p1, y = p2 } + | InfixCon arg arg -- p1 `C` p2 + deriving Data + +-- | An empty list that can be used to indicate that there are no +-- type arguments allowed in cases where HsConDetails is applied to Void. +noTypeArgs :: [Void] +noTypeArgs = [] + +instance (Outputable tyarg, Outputable arg, Outputable rec) + => Outputable (HsConDetails tyarg arg rec) where + ppr (PrefixCon tyargs args) = text "PrefixCon:" <+> hsep (map (\t -> text "@" <> ppr t) tyargs) <+> ppr args + ppr (RecCon rec) = text "RecCon:" <+> ppr rec + ppr (InfixCon l r) = text "InfixCon:" <+> ppr [l, r] + +{- +Note [ConDeclField passs] +~~~~~~~~~~~~~~~~~~~~~~~~~ + +A ConDeclField contains a list of field occurrences: these always +include the field label as the user wrote it. After the renamer, it +will additionally contain the identity of the selector function in the +second component. + +Due to DuplicateRecordFields, the OccName of the selector function +may have been mangled, which is why we keep the original field label +separately. For example, when DuplicateRecordFields is enabled + + data T = MkT { x :: Int } + +gives + + ConDeclField { cd_fld_names = [L _ (FieldOcc "x" $sel:x:MkT)], ... }. +-} + +----------------------- +-- A valid type must have a for-all at the top of the type, or of the fn arg +-- types + +--------------------- + +{- Note [Scoping of named wildcards] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Consider + f :: _a -> _a + f x = let g :: _a -> _a + g = ... + in ... + +Currently, for better or worse, the "_a" variables are all the same. So +although there is no explicit forall, the "_a" scopes over the definition. +I don't know if this is a good idea, but there it is. +-} + +{- Note [hsScopedTvs and visible foralls] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +-XScopedTypeVariables can be defined in terms of a desugaring to +-XTypeAbstractions (GHC Proposal #50): + + fn :: forall a b c. tau(a,b,c) fn :: forall a b c. tau(a,b,c) + fn = defn(a,b,c) ==> fn @x @y @z = defn(x,y,z) + +That is, for every type variable of the leading 'forall' in the type signature, +we add an invisible binder at term level. + +This model does not extend to visible forall, as discussed here: + +* https://gitlab.haskell.org/ghc/ghc/issues/16734#note_203412 +* https://github.com/ghc-proposals/ghc-proposals/pull/238 + +The conclusion of these discussions can be summarized as follows: + + > Assuming support for visible 'forall' in terms, consider this example: + > + > vfn :: forall x y -> tau(x,y) + > vfn = \a b -> ... + > + > The user has written their own binders 'a' and 'b' to stand for 'x' and + > 'y', and we definitely should not desugar this into: + > + > vfn :: forall x y -> tau(x,y) + > vfn x y = \a b -> ... -- bad! + +This design choice is reflected in the design of HsOuterSigTyVarBndrs, which are +used in every place that ScopedTypeVariables takes effect: + + data HsOuterTyVarBndrs flag pass + = HsOuterImplicit { ... } + | HsOuterExplicit { ..., hso_bndrs :: [LHsTyVarBndr flag pass] } + | ... + type HsOuterSigTyVarBndrs = HsOuterTyVarBndrs Specificity + +The HsOuterExplicit constructor is only used in type signatures with outermost, +/invisible/ 'forall's. Any other type—including those with outermost, +/visible/ 'forall's—will use HsOuterImplicit. Therefore, when we determine +which type variables to bring into scope over the body of a function +(in hsScopedTvs), we /only/ bring the type variables bound by the hso_bndrs in +an HsOuterExplicit into scope. If we have an HsOuterImplicit instead, then we +do not bring any type variables into scope over the body of a function at all. + +At the moment, GHC does not support visible 'forall' in terms. Nevertheless, +it is still possible to write erroneous programs that use visible 'forall's in +terms, such as this example: + + x :: forall a -> a -> a + x = x + +Previous versions of GHC would bring `a` into scope over the body of `x` in the +hopes that the typechecker would error out later +(see `GHC.Tc.Validity.vdqAllowed`). However, this can wreak havoc in the +renamer before GHC gets to that point (see #17687 for an example of this). +Bottom line: nip problems in the bud by refraining from bringing any type +variables in an HsOuterImplicit into scope over the body of a function, even +if they correspond to a visible 'forall'. +-} + +{- +************************************************************************ +* * + Decomposing HsTypes +* * +************************************************************************ +-} + +-- Arguments in an expression/type after splitting +data HsArg tm ty + = HsValArg tm -- Argument is an ordinary expression (f arg) + | HsTypeArg SrcSpan ty -- Argument is a visible type application (f @ty) + -- SrcSpan is location of the `@` + | HsArgPar SrcSpan -- See Note [HsArgPar] + +numVisibleArgs :: [HsArg tm ty] -> Arity +numVisibleArgs = count is_vis + where is_vis (HsValArg _) = True + is_vis _ = False + +-- type level equivalent +type LHsTypeArg p = HsArg (LHsType p) (LHsKind p) + +instance (Outputable tm, Outputable ty) => Outputable (HsArg tm ty) where + ppr (HsValArg tm) = ppr tm + ppr (HsTypeArg _ ty) = char '@' <> ppr ty + ppr (HsArgPar sp) = text "HsArgPar" <+> ppr sp +{- +Note [HsArgPar] +A HsArgPar indicates that everything to the left of this in the argument list is +enclosed in parentheses together with the function itself. It is necessary so +that we can recreate the parenthesis structure in the original source after +typechecking the arguments. + +The SrcSpan is the span of the original HsPar + +((f arg1) arg2 arg3) results in an input argument list of +[HsValArg arg1, HsArgPar span1, HsValArg arg2, HsValArg arg3, HsArgPar span2] + +-} + +-------------------------------- + + +{- +************************************************************************ +* * + FieldOcc +* * +************************************************************************ +-} + +-- | Located Field Occurrence +type LFieldOcc pass = XRec pass (FieldOcc pass) + +-- | Field Occurrence +-- +-- Represents an *occurrence* of an unambiguous field. This may or may not be a +-- binding occurrence (e.g. this type is used in 'ConDeclField' and +-- 'RecordPatSynField' which bind their fields, but also in 'HsRecField' for +-- record construction and patterns, which do not). +-- +-- We store both the 'RdrName' the user originally wrote, and after the renamer, +-- the selector function. +data FieldOcc pass = FieldOcc { extFieldOcc :: XCFieldOcc pass + , rdrNameFieldOcc :: Located RdrName + -- ^ See Note [Located RdrNames] in "GHC.Hs.Expr" + } + + | XFieldOcc + !(XXFieldOcc pass) + +deriving instance (Eq (XCFieldOcc pass), Eq (XXFieldOcc pass)) => Eq (FieldOcc pass) + +instance Outputable (FieldOcc pass) where + ppr = ppr . rdrNameFieldOcc + + +-- | Ambiguous Field Occurrence +-- +-- Represents an *occurrence* of a field that is potentially +-- ambiguous after the renamer, with the ambiguity resolved by the +-- typechecker. We always store the 'RdrName' that the user +-- originally wrote, and store the selector function after the renamer +-- (for unambiguous occurrences) or the typechecker (for ambiguous +-- occurrences). +-- +-- See Note [HsRecField and HsRecUpdField] in "GHC.Hs.Pat" and +-- Note [Disambiguating record fields] in "GHC.Tc.Gen.Head". +-- See Note [Located RdrNames] in "GHC.Hs.Expr" +data AmbiguousFieldOcc pass + = Unambiguous (XUnambiguous pass) (Located RdrName) + | Ambiguous (XAmbiguous pass) (Located RdrName) + | XAmbiguousFieldOcc !(XXAmbiguousFieldOcc pass) + + +{- +************************************************************************ +* * +\subsection{Pretty printing} +* * +************************************************************************ +-} + +instance Outputable HsTyLit where + ppr = ppr_tylit +-------------------------- +ppr_tylit :: HsTyLit -> SDoc +ppr_tylit (HsNumTy source i) = pprWithSourceText source (integer i) +ppr_tylit (HsStrTy source s) = pprWithSourceText source (text (show s)) |