[Git][ghc/ghc][master] Don't use substTyUnchecked in newMetaTyVar

[Marge Bot (@marge-bot)]

Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC


Commits:
eb1a6ab1 by sheaf at 2023-07-16T09:20:45-04:00
Don't use substTyUnchecked in newMetaTyVar

There were some comments that explained that we needed to use an
unchecked substitution function because of issue #12931, but that
has since been fixed, so we should be able to use substTy instead now.

- - - - -


1 changed file:

- compiler/GHC/Tc/Utils/TcMType.hs


Changes:

=====================================
compiler/GHC/Tc/Utils/TcMType.hs
=====================================
@@ -1001,16 +1001,7 @@ new_meta_tv_x info subst tv
         ; let subst1 = extendTvSubstWithClone subst tv new_tv
         ; return (subst1, new_tv) }
   where
-    substd_kind = substTyUnchecked subst (tyVarKind tv)
-      -- NOTE: #12549 is fixed so we could use
-      -- substTy here, but the tc_infer_args problem
-      -- is not yet fixed so leaving as unchecked for now.
-      -- OLD NOTE:
-      -- Unchecked because we call newMetaTyVarX from
-      -- tcInstTyBinder, which is called from tcInferTyApps
-      -- which does not yet take enough trouble to ensure
-      -- the in-scope set is right; e.g. #12785 trips
-      -- if we use substTy here
+    substd_kind = substTy subst (tyVarKind tv)
 
 newMetaTyVarTyAtLevel :: TcLevel -> TcKind -> TcM TcType
 newMetaTyVarTyAtLevel tc_lvl kind



View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/eb1a6ab1df473c7ec0e1cbb20fc7124706326ce1

-- 
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/eb1a6ab1df473c7ec0e1cbb20fc7124706326ce1
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