diff options
| author | Ryan Scott <ryan.gl.scott@gmail.com> | 2022-01-26 06:59:51 -0500 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2022-01-27 02:40:47 -0500 |
| commit | f0adea14316ef476607cb7d99f74875875e52b20 (patch) | |
| tree | 2e4c288bbcc5aa9a80468b37fbc87e85664b0194 /compiler/GHC/Tc | |
| parent | 0573aeab1381680fe86a13960a7fcdb98a69aa58 (diff) | |
| download | haskell-f0adea14316ef476607cb7d99f74875875e52b20.tar.gz | |
Expand type synonyms in markNominal
`markNominal` is repsonsible for setting the roles of type variables
that appear underneath an `AppTy` to be nominal. However, `markNominal`
previously did not expand type synonyms, so in a data type like this:
```hs
data M f a = MkM (f (T a))
type T a = Int
```
The `a` in `M f a` would be marked nominal, even though `T a` would simply
expand to `Int`. The fix is simple: call `coreView` as appropriate in
`markNominal`. This is much like the fix for #14101, but in a different spot.
Fixes #20999.
Diffstat (limited to 'compiler/GHC/Tc')
| -rw-r--r-- | compiler/GHC/Tc/TyCl/Utils.hs | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/compiler/GHC/Tc/TyCl/Utils.hs b/compiler/GHC/Tc/TyCl/Utils.hs index 347a7e57ff..7abde66296 100644 --- a/compiler/GHC/Tc/TyCl/Utils.hs +++ b/compiler/GHC/Tc/TyCl/Utils.hs @@ -651,6 +651,8 @@ markNominal lcls ty = let nvars = fvVarList (FV.delFVs lcls $ get_ty_vars ty) in -- recurring into coercions. Recall: coercions are totally ignored during -- role inference. See [Coercions in role inference] get_ty_vars :: Type -> FV + get_ty_vars t | Just t' <- coreView t -- #20999 + = get_ty_vars t' get_ty_vars (TyVarTy tv) = unitFV tv get_ty_vars (AppTy t1 t2) = get_ty_vars t1 `unionFV` get_ty_vars t2 get_ty_vars (FunTy _ w t1 t2) = get_ty_vars w `unionFV` get_ty_vars t1 `unionFV` get_ty_vars t2 |