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, 5 insertions, 5 deletions

diff --git a/compiler/main/InteractiveEval.hs b/compiler/main/InteractiveEval.hs
index 8b5a6b6af7..8e396cc16a 100644
--- a/compiler/main/InteractiveEval.hs
+++ b/compiler/main/InteractiveEval.hs
@@ -246,7 +246,7 @@ withVirtualCWD m = do
 
   gbracket set_cwd reset_cwd $ \_ -> m
 
-parseImportDecl :: GhcMonad m => String -> m (ImportDecl RdrName)
+parseImportDecl :: GhcMonad m => String -> m (ImportDecl GhcPs)
 parseImportDecl expr = withSession $ \hsc_env -> liftIO $ hscImport hsc_env expr
 
 emptyHistory :: Int -> BoundedList History
@@ -674,7 +674,7 @@ findGlobalRdrEnv hsc_env imports
            ([], imods_env) -> Right (foldr plusGlobalRdrEnv idecls_env imods_env)
            (err : _, _)    -> Left err }
   where
-    idecls :: [LImportDecl RdrName]
+    idecls :: [LImportDecl GhcPs]
     idecls = [noLoc d | IIDecl d <- imports]
 
     imods :: [ModuleName]
@@ -841,7 +841,7 @@ typeKind normalise str = withSession $ \hsc_env -> do
 
 -- | Parse an expression, the parsed expression can be further processed and
 -- passed to compileParsedExpr.
-parseExpr :: GhcMonad m => String -> m (LHsExpr RdrName)
+parseExpr :: GhcMonad m => String -> m (LHsExpr GhcPs)
 parseExpr expr = withSession $ \hsc_env -> do
   liftIO $ runInteractiveHsc hsc_env $ hscParseExpr expr
 
@@ -859,7 +859,7 @@ compileExprRemote expr = do
 
 -- | Compile an parsed expression (before renaming), run it and deliver
 -- the resulting HValue.
-compileParsedExprRemote :: GhcMonad m => LHsExpr RdrName -> m ForeignHValue
+compileParsedExprRemote :: GhcMonad m => LHsExpr GhcPs -> m ForeignHValue
 compileParsedExprRemote expr@(L loc _) = withSession $ \hsc_env -> do
   -- > let _compileParsedExpr = expr
   -- Create let stmt from expr to make hscParsedStmt happy.
@@ -879,7 +879,7 @@ compileParsedExprRemote expr@(L loc _) = withSession $ \hsc_env -> do
       liftIO $ throwIO (fromSerializableException e)
     _ -> panic "compileParsedExpr"
 
-compileParsedExpr :: GhcMonad m => LHsExpr RdrName -> m HValue
+compileParsedExpr :: GhcMonad m => LHsExpr GhcPs -> m HValue
 compileParsedExpr expr = do
    fhv <- compileParsedExprRemote expr
    dflags <- getDynFlags