[project @ 2005-02-03 13:11:44 by simonpj]

Fix another substitution-related bug in CoreLint

diff --git a/ghc/compiler/coreSyn/CoreLint.lhs b/ghc/compiler/coreSyn/CoreLint.lhs
index 33387c7..60ddc5c 100644 (file)
--- a/ghc/compiler/coreSyn/CoreLint.lhs
+++ b/ghc/compiler/coreSyn/CoreLint.lhs
@@ -33,7 +33,7 @@ import Type           ( Type, tyVarsOfType, coreEqType,
                          isUnLiftedType, typeKind, mkForAllTy, mkFunTy,
                          isUnboxedTupleType, isSubKind,
                          substTyWith, emptyTvSubst, extendTvInScope, 
-                         TvSubst, TvSubstEnv, setTvSubstEnv, substTy,
+                         TvSubst, TvSubstEnv, mkTvSubst, setTvSubstEnv, substTy,
                          extendTvSubst, composeTvSubst, isInScope,
                          getTvSubstEnv, getTvInScope )
 import TyCon           ( isPrimTyCon )
@@ -425,9 +425,8 @@ checkAltExpr expr ann_ty
   = do { actual_ty <- lintCoreExpr expr 
        ; checkTys actual_ty ann_ty (mkCaseAltMsg expr actual_ty ann_ty) }
 
-lintCoreAlt :: Type                    -- Type of scrutinee; a fixed point of 
-                                       --                    the substitution
-            -> Type                     -- Type of the alternative
+lintCoreAlt :: OutType                 -- Type of scrutinee
+            -> OutType          -- Type of the alternative
            -> CoreAlt
            -> LintM ()
 
@@ -437,8 +436,7 @@ lintCoreAlt scrut_ty alt_ty alt@(DEFAULT, args, rhs) =
 
 lintCoreAlt scrut_ty alt_ty alt@(LitAlt lit, args, rhs) = 
   do { checkL (null args) (mkDefaultArgsMsg args)
-     ; checkTys lit_ty scrut_ty
-         (mkBadPatMsg lit_ty scrut_ty) 
+     ; checkTys lit_ty scrut_ty (mkBadPatMsg lit_ty scrut_ty)  
      ; checkAltExpr rhs alt_ty } 
   where
     lit_ty = literalType lit
@@ -477,7 +475,11 @@ lintCoreAlt scrut_ty alt_ty alt@(DataAlt con, args, rhs)
        ; con_type <- lintTyApps (dataConRepType con) tvs'
        ; mapM lintBinder ids   -- Lint Ids in the refined world
        ; lintCoreArgs con_type (map Var ids)
-       ; checkAltExpr rhs alt_ty
+       ; let refined_alt_ty = substTy (mkTvSubst in_scope refine) alt_ty
+               -- alt_ty is already an OutType, so don't re-apply 
+               -- the current substitution.  But we must apply the
+               -- refinement so that the check in checkAltExpr is ok
+       ; checkAltExpr rhs refined_alt_ty
     } } }
 
   | otherwise  -- Scrut-ty is wrong shape