From da92e7288fe9c0e83768b7dd0898bca30b9ff2ce Mon Sep 17 00:00:00 2001
From: Matthew Pickering <matthewtpickering@gmail.com>
Date: Tue, 13 Apr 2021 16:39:46 +0100
Subject: hie: Initialise the proper environment for calling dsExpr

We now use DsM as the base monad for writing hie files and properly
initialise it from the TcGblEnv.

Before, we would end up reading the interface file from disk for the
module we were currently compiling. The modules iface then ended up in
the EPS causing all sorts of subtle
carnage, including difference in the generated core and haddock emitting
a lot of warnings. With the fix, the
module in the TcGblEnv is set correctly so the lookups happen in the
local name env rather than thinking the identifier comes from an
external package.

Fixes #19693 and #19334
---
 compiler/GHC/Iface/Ext/Ast.hs | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

(limited to 'compiler/GHC/Iface/Ext/Ast.hs')

diff --git a/compiler/GHC/Iface/Ext/Ast.hs b/compiler/GHC/Iface/Ext/Ast.hs
index 6f894dfc1a..5a787f5b94 100644
--- a/compiler/GHC/Iface/Ext/Ast.hs
+++ b/compiler/GHC/Iface/Ext/Ast.hs
@@ -37,7 +37,6 @@ import GHC.Core.ConLike           ( conLikeName, ConLike(RealDataCon) )
 import GHC.Core.TyCon             ( TyCon, tyConClass_maybe )
 import GHC.Core.FVs
 import GHC.Core.DataCon           ( dataConNonlinearType )
-import GHC.HsToCore               ( deSugarExpr )
 import GHC.Types.FieldLabel
 import GHC.Hs
 import GHC.Driver.Env
@@ -78,6 +77,9 @@ import Control.Monad              ( forM_ )
 import Control.Monad.Trans.State.Strict
 import Control.Monad.Trans.Reader
 import Control.Monad.Trans.Class  ( lift )
+import GHC.HsToCore.Types
+import GHC.HsToCore.Expr
+import GHC.HsToCore.Monad
 
 {- Note [Updating HieAst for changes in the GHC AST]
 
@@ -278,7 +280,7 @@ modifyState = foldr go id
       = addSubstitution mono poly . f
     go _ f = f
 
-type HieM = ReaderT NodeOrigin (StateT HieState Hsc)
+type HieM = ReaderT NodeOrigin (StateT HieState DsM)
 
 -- | Construct an 'HieFile' from the outputs of the typechecker.
 mkHieFile :: ModSummary
@@ -301,7 +303,9 @@ mkHieFileWithSource src_file src ms ts rs = do
       top_ev_binds = tcg_ev_binds ts
       insts = tcg_insts ts
       tcs = tcg_tcs ts
-  (asts', arr) <- getCompressedAsts tc_binds rs top_ev_binds insts tcs
+  hsc_env <- Hsc $ \e w -> return (e, w)
+  (_msgs, res) <- liftIO $ initDs hsc_env ts $ getCompressedAsts tc_binds rs top_ev_binds insts tcs
+  let (asts',arr) = expectJust "mkHieFileWithSource" res
   return $ HieFile
       { hie_hs_file = src_file
       , hie_module = ms_mod ms
@@ -313,13 +317,13 @@ mkHieFileWithSource src_file src ms ts rs = do
       }
 
 getCompressedAsts :: TypecheckedSource -> RenamedSource -> Bag EvBind -> [ClsInst] -> [TyCon]
-  -> Hsc (HieASTs TypeIndex, A.Array TypeIndex HieTypeFlat)
+  -> DsM (HieASTs TypeIndex, A.Array TypeIndex HieTypeFlat)
 getCompressedAsts ts rs top_ev_binds insts tcs = do
   asts <- enrichHie ts rs top_ev_binds insts tcs
   return $ compressTypes asts
 
 enrichHie :: TypecheckedSource -> RenamedSource -> Bag EvBind -> [ClsInst] -> [TyCon]
-  -> Hsc (HieASTs Type)
+  -> DsM (HieASTs Type)
 enrichHie ts (hsGrp, imports, exports, _) ev_bs insts tcs =
   flip evalStateT initState $ flip runReaderT SourceInfo $ do
     tasts <- toHie $ fmap (BC RegularBind ModuleScope) ts
@@ -753,9 +757,10 @@ instance HiePass p => HasType (LocatedA (HsExpr (GhcPass p))) where
           Nothing
             | skipDesugaring e' -> fallback
             | otherwise -> do
-                hs_env <- lift $ lift $ Hsc $ \e w -> return (e,w)
-                (_,mbe) <- liftIO $ deSugarExpr hs_env e
-                maybe fallback (makeTypeNodeA e' spn . exprType) mbe
+                (e, no_errs) <- lift $ lift $ discardWarningsDs $ askNoErrsDs $ dsLExpr e
+                if no_errs
+                  then makeTypeNodeA e' spn . exprType $ e
+                  else fallback
         where
           fallback = makeNodeA e' spn
 
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