| Commit message (Collapse) | Author | Age | Files | Lines |
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`DsMeta.rep_sig` used to skip over `FixSig` entirely, which had the
effect of causing local fixity declarations to be dropped when quoted
in Template Haskell. But there is no good reason for this state of
affairs, as the code in `DsMeta.repFixD` (which handles top-level
fixity declarations) handles local fixity declarations just fine.
This patch factors out the necessary parts of `repFixD` so that they
can be used in `rep_sig` as well.
There was one minor complication: the fixity signatures for class
methods in each `HsGroup` were stored both in `FixSig`s _and_ the
list of `LFixitySig`s for top-level fixity signatures, so I needed
to take action to prevent fixity signatures for class methods being
converted to `Dec`s twice. I tweaked `RnSource.add` to avoid putting
these fixity signatures in two places and added
`Note [Top-level fixity signatures in an HsGroup]` in `GHC.Hs.Decls`
to explain the new design.
Fixes #17608. Bumps the Haddock submodule.
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This patch implements overloaded quotation brackets which generalise the
desugaring of all quotation forms in terms of a new minimal interface.
The main change is that a quotation, for example, [e| 5 |], will now
have type `Quote m => m Exp` rather than `Q Exp`. The `Quote` typeclass
contains a single method for generating new names which is used when
desugaring binding structures.
The return type of functions from the `Lift` type class, `lift` and `liftTyped` have
been restricted to `forall m . Quote m => m Exp` rather than returning a
result in a Q monad.
More details about the feature can be read in the GHC proposal.
https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0246-overloaded-bracket.rst
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Before this patch, GHC always printed the * kind unparenthesized.
This led to two issues:
1. Sometimes GHC printed invalid or incorrect code.
For example, GHC would print: type F @* x = x
when it meant to print: type F @(*) x = x
In the former case, instead of a kind application we were getting a
type operator (@*).
2. Sometimes GHC printed kinds that were correct but hard to read.
Should Either * Int be read as Either (*) Int
or as (*) Either Int ?
This depends on whether -XStarIsType is enabled, but it would be
easier if we didn't have to check for the flag when reading the code.
We can solve both problems by assigning (*) a different precedence. Note
that Haskell98 kinds are not affected:
((* -> *) -> *) -> * does NOT become (((*) -> (*)) -> (*)) -> (*)
The parentheses are added when (*) is used in a function argument
position:
F * * * becomes F (*) (*) (*)
F A * B becomes F A (*) B
Proxy * becomes Proxy (*)
a * -> * becomes a (*) -> *
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As suggested by RyanGlScott in !2163.
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Metric Decrease:
haddock.compiler
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This is a refactoring with no user-visible changes (except for GHC API
users). Consider the HsExpr constructors that correspond to user-written
pragmas:
HsSCC representing {-# SCC ... #-}
HsCoreAnn representing {-# CORE ... #-}
HsTickPragma representing {-# GENERATED ... #-}
We can factor them out into a separate datatype, HsPragE. It makes the
code a bit tidier, especially in the parser.
Before this patch:
hpc_annot :: { Located ( (([AddAnn],SourceText),(StringLiteral,(Int,Int),(Int,Int))),
((SourceText,SourceText),(SourceText,SourceText))
) }
After this patch:
prag_hpc :: { Located ([AddAnn], HsPragE GhcPs) }
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This patch implements a part of GHC Proposal #229 that covers five
operators:
* the bang operator (!)
* the tilde operator (~)
* the at operator (@)
* the dollar operator ($)
* the double dollar operator ($$)
Based on surrounding whitespace, these operators are disambiguated into
bang patterns, lazy patterns, strictness annotations, type
applications, splices, and typed splices.
This patch doesn't cover the (-) operator or the -Woperator-whitespace
warning, which are left as future work.
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In #17270 we have the pattern-match checker emit incorrect warnings. The
reason for that behavior is ultimately an inconsistency in whether we
treat TH splices as written by the user (`FromSource :: Origin`) or as
generated code (`Generated`). This was first reported in #14838.
The current solution is to TH splices as `Generated` by default and only
treat them as `FromSource` when the user requests so
(-fenable-th-splice-warnings). There are multiple reasons for opt-in
rather than opt-out:
* It's not clear that the user that compiles a splice is the author of the code
that produces the warning. Think of the situation where she just splices in
code from a third-party library that produces incomplete pattern matches.
In this scenario, the user isn't even able to fix that warning.
* Gathering information for producing the warnings (pattern-match check
warnings in particular) is costly. There's no point in doing so if the user
is not interested in those warnings.
Fixes #17270, but not #14838, because the proper solution needs a GHC
proposal extending the TH AST syntax.
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This reverts the change in #9096.
The specialcasing done for prefix (->) is brittle and
does not support VTA, type families, type synonyms etc.
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This makes error messages a tad less noisy.
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Issue #17461 was occurring because the `Outputable` instance for
standalone kind signatures was simply calling `ppr` on the name in
the kind signature, which does not add parentheses to infix names.
The solution is simple: use `pprPrefixOcc` instead.
Fixes #17461.
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Previously an import cycle between Type and TyCoRep meant that several
functions in TyCoRep ended up SOURCE import coreView. This is quite
unfortunate as coreView is intended to be fused into a larger pattern
match and not incur an extra call.
Fix this with a bit of restructuring:
* Move the functions in `TyCoRep` which depend upon things in `Type`
into `Type`
* Fold contents of `Kind` into `Type` and turn `Kind` into a simple
wrapper re-exporting kind-ish things from `Type`
* Clean up the redundant imports that popped up as a result
Closes #17441.
Metric Decrease:
T4334
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!1906 left some loose ends in regards to Template Haskell's treatment
of unary tuples. This patch ends to tie up those loose ends:
* In addition to having `TupleT 1` produce unary tuples, `TupE [exp]`
and `TupP [pat]` also now produce unary tuples.
* I have added various special cases in GHC's pretty-printers to
ensure that explicit 1-tuples are printed using the `Unit` type.
See `testsuite/tests/th/T17380`.
* The GHC 8.10.1 release notes entry has been tidied up a little.
Fixes #16881. Fixes #17371. Fixes #17380.
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Since the Trees That Grow effort started, we had `type LPat = Pat`.
This is so that `SrcLoc`s would only be annotated in GHC's AST, which is
the reason why all GHC passes use the extension constructor `XPat` to
attach source locations. See #15495 for the design discussion behind
that.
But now suddenly there are `XPat`s everywhere!
There are several functions which dont't cope with `XPat`s by either
crashing (`hsPatType`) or simply returning incorrect results
(`collectEvVarsPat`).
This issue was raised in #17330. I also came up with a rather clean and
type-safe solution to the problem: We define
```haskell
type family XRec p (f :: * -> *) = r | r -> p f
type instance XRec (GhcPass p) f = Located (f (GhcPass p))
type instance XRec TH f = f p
type LPat p = XRec p Pat
```
This is a rather modular embedding of the old "ping-pong" style, while
we only pay for the `Located` wrapper within GHC. No ping-ponging in
a potential Template Haskell AST, for example. Yet, we miss no case
where we should've handled a `SrcLoc`: `hsPatType` and
`collectEvVarsPat` are not callable at an `LPat`.
Also, this gets rid of one indirection in `Located` variants:
Previously, we'd have to go through `XPat` and `Located` to get from
`LPat` to the wrapped `Pat`. Now it's just `Located` again.
Thus we fix #17330.
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with equality constraints
In #17304, Richard and Simon dicovered that using `-XFlexibleInstances`
for `Outputable` instances of AST data types means users can provide orphan
`Outputable` instances for passes other than `GhcPass`.
Type inference doesn't currently to suffer, and Richard gave an example
in #17304 that shows how rare a case would be where the slightly worse
type inference would matter.
So I went ahead with the refactoring, attempting to fix #17304.
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Applicative-do has a bug where it fails to use the monadic fail method
when desugaring patternmatches which can fail. See #15344.
This patch fixes that problem. It required more rewiring than I had expected.
Applicative-do happens mostly in the renamer; that's where decisions about
scheduling are made. This schedule is then carried through the typechecker and
into the desugarer which performs the actual translation. Fixing this bug
required sending information about the fail method from the renamer, through
the type checker and into the desugarer. Previously, the desugarer didn't
have enough information to actually desugar pattern matches correctly.
As a side effect, we also fix #16628, where GHC wouldn't catch missing
MonadFail instances with -XApplicativeDo.
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Previously, all constraints from all top-level groups (as
separated by top-level splices) were lumped together and solved
at the end. This could leak metavariables to TH, though, and
that's bad. This patch solves each group's constraints before
running the next group's splice.
Naturally, we now report fewer errors in some cases.
One nice benefit is that this also fixes #11680, but in a much
simpler way than the original fix for that ticket. Admittedly,
the error messages degrade just a bit from the fix from #11680
(previously, we informed users about variables that will be
brought into scope below a top-level splice, and now we just
report an out-of-scope error), but the amount of complexity
required throughout GHC to get that error was just not worth it.
This patch thus reverts much of
f93c9517a2c6e158e4a5c5bc7a3d3f88cb4ed119.
Fixes #16980
Test cases: th/T16980{,a}
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This patch also changes the way we handle empty lists, simplifying
them somewhat. See Note [Empty lists]. Previously, we had to
special-case empty lists in the type-checker. Now no more!
Finally, this patch improves some documentation around the ir_inst
field used in the type-checker.
This breaks a test case, but I really think the problem is #17251,
not really related to this patch.
Test case: typecheck/should_compile/T13680
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Implements GHC Proposal #54: .../ghc-proposals/blob/master/proposals/0054-kind-signatures.rst
With this patch, a type constructor can now be given an explicit
standalone kind signature:
{-# LANGUAGE StandaloneKindSignatures #-}
type Functor :: (Type -> Type) -> Constraint
class Functor f where
fmap :: (a -> b) -> f a -> f b
This is a replacement for CUSKs (complete user-specified
kind signatures), which are now scheduled for deprecation.
User-facing changes
-------------------
* A new extension flag has been added, -XStandaloneKindSignatures, which
implies -XNoCUSKs.
* There is a new syntactic construct, a standalone kind signature:
type <name> :: <kind>
Declarations of data types, classes, data families, type families, and
type synonyms may be accompanied by a standalone kind signature.
* A standalone kind signature enables polymorphic recursion in types,
just like a function type signature enables polymorphic recursion in
terms. This obviates the need for CUSKs.
* TemplateHaskell AST has been extended with 'KiSigD' to represent
standalone kind signatures.
* GHCi :info command now prints the kind signature of type constructors:
ghci> :info Functor
type Functor :: (Type -> Type) -> Constraint
...
Limitations
-----------
* 'forall'-bound type variables of a standalone kind signature do not
scope over the declaration body, even if the -XScopedTypeVariables is
enabled. See #16635 and #16734.
* Wildcards are not allowed in standalone kind signatures, as partial
signatures do not allow for polymorphic recursion.
* Associated types may not be given an explicit standalone kind
signature. Instead, they are assumed to have a CUSK if the parent class
has a standalone kind signature and regardless of the -XCUSKs flag.
* Standalone kind signatures do not support multiple names at the moment:
type T1, T2 :: Type -> Type -- rejected
type T1 = Maybe
type T2 = Either String
See #16754.
* Creative use of equality constraints in standalone kind signatures may
lead to GHC panics:
type C :: forall (a :: Type) -> a ~ Int => Constraint
class C a where
f :: C a => a -> Int
See #16758.
Implementation notes
--------------------
* The heart of this patch is the 'kcDeclHeader' function, which is used to
kind-check a declaration header against its standalone kind signature.
It does so in two rounds:
1. check user-written binders
2. instantiate invisible binders a la 'checkExpectedKind'
* 'kcTyClGroup' now partitions declarations into declarations with a
standalone kind signature or a CUSK (kinded_decls) and declarations
without either (kindless_decls):
* 'kinded_decls' are kind-checked with 'checkInitialKinds'
* 'kindless_decls' are kind-checked with 'getInitialKinds'
* DerivInfo has been extended with a new field:
di_scoped_tvs :: ![(Name,TyVar)]
These variables must be added to the context in case the deriving clause
references tcTyConScopedTyVars. See #16731.
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Add GHC.Hs module hierarchy replacing hsSyn.
Metric Increase:
haddock.compiler
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