Udate hsSyn AST to use Trees that Grow

Summary:
See https://ghc.haskell.org/trac/ghc/wiki/ImplementingTreesThatGrow

This commit prepares the ground for a full extensible AST, by replacing the type
parameter for the hsSyn data types with a set of indices into type families,

    data GhcPs -- ^ Index for GHC parser output
    data GhcRn -- ^ Index for GHC renamer output
    data GhcTc -- ^ Index for GHC typechecker output

These are now used instead of `RdrName`, `Name` and `Id`/`TcId`/`Var`

Where the original name type is required in a polymorphic context, this is
accessible via the IdP type family, defined as

    type family IdP p
    type instance IdP GhcPs = RdrName
    type instance IdP GhcRn = Name
    type instance IdP GhcTc = Id

These types are declared in the new 'hsSyn/HsExtension.hs' module.

To gain a better understanding of the extension mechanism, it has been applied
to `HsLit` only, also replacing the `SourceText` fields in them with extension
types.

To preserve extension generality, a type class is introduced to capture the
`SourceText` interface, which must be honoured by all of the extension points
which originally had a `SourceText`.  The class is defined as

    class HasSourceText a where
      -- Provide setters to mimic existing constructors
      noSourceText  :: a
      sourceText    :: String -> a

      setSourceText :: SourceText -> a
      getSourceText :: a -> SourceText

And the constraint is captured in `SourceTextX`, which is a constraint type
listing all the extension points that make use of the class.

Updating Haddock submodule to match.

Test Plan: ./validate

Reviewers: simonpj, shayan-najd, goldfire, austin, bgamari

Subscribers: rwbarton, thomie, mpickering

Differential Revision: https://phabricator.haskell.org/D3609

1 files changed, 0 insertions, 50 deletions

diff --git a/compiler/hsSyn/PlaceHolder.hs b/compiler/hsSyn/PlaceHolder.hs
index 2e195df799..5c716d259c 100644
--- a/compiler/hsSyn/PlaceHolder.hs
+++ b/compiler/hsSyn/PlaceHolder.hs
@@ -12,14 +12,8 @@ import Name
 import NameSet
 import RdrName
 import Var
-import Coercion
-import ConLike (ConLike)
-import FieldLabel
-import SrcLoc (Located)
-import TcEvidence ( HsWrapper )
 
 import Data.Data hiding ( Fixity )
-import BasicTypes       (Fixity)
 
 
 {-
@@ -37,18 +31,6 @@ import BasicTypes       (Fixity)
 data PlaceHolder = PlaceHolder
   deriving (Data)
 
--- | Types that are not defined until after type checking
-type family PostTc id ty  -- Note [Pass sensitive types]
-type instance PostTc Id      ty = ty
-type instance PostTc Name    ty = PlaceHolder
-type instance PostTc RdrName ty = PlaceHolder
-
--- | Types that are not defined until after renaming
-type family PostRn id ty  -- Note [Pass sensitive types]
-type instance PostRn Id      ty = ty
-type instance PostRn Name    ty = ty
-type instance PostRn RdrName ty = PlaceHolder
-
 placeHolderKind :: PlaceHolder
 placeHolderKind = PlaceHolder
 
@@ -103,31 +85,6 @@ DataId constraint type based on this, so even though it is safe the
 UndecidableInstances pragma is required where this is used.
 -}
 
-type DataId id =
-  ( DataIdPost id
-  , DataIdPost (NameOrRdrName id)
-  )
-
-type DataIdPost id =
-  ( Data id
-  , Data (PostRn id NameSet)
-  , Data (PostRn id Fixity)
-  , Data (PostRn id Bool)
-  , Data (PostRn id Name)
-  , Data (PostRn id (Located Name))
-  , Data (PostRn id [Name])
-
-  , Data (PostRn id id)
-  , Data (PostTc id Type)
-  , Data (PostTc id Coercion)
-  , Data (PostTc id id)
-  , Data (PostTc id [Type])
-  , Data (PostTc id ConLike)
-  , Data (PostTc id [ConLike])
-  , Data (PostTc id HsWrapper)
-  , Data (PostTc id [FieldLabel])
-  )
-
 
 -- |Follow the @id@, but never beyond Name. This is used in a 'HsMatchContext',
 -- for printing messages related to a 'Match'
@@ -135,10 +92,3 @@ type family NameOrRdrName id where
   NameOrRdrName Id      = Name
   NameOrRdrName Name    = Name
   NameOrRdrName RdrName = RdrName
-
--- |Constraint type to bundle up the requirement for 'OutputableBndr' on both
--- the @id@ and the 'NameOrRdrName' type for it
-type OutputableBndrId id =
-  ( OutputableBndr id
-  , OutputableBndr (NameOrRdrName id)
-  )