diff options
Diffstat (limited to 'compiler/GHC/Tc/Errors/Types.hs')
| -rw-r--r-- | compiler/GHC/Tc/Errors/Types.hs | 37 |
1 files changed, 37 insertions, 0 deletions
diff --git a/compiler/GHC/Tc/Errors/Types.hs b/compiler/GHC/Tc/Errors/Types.hs index c1b8461839..5cb94bac68 100644 --- a/compiler/GHC/Tc/Errors/Types.hs +++ b/compiler/GHC/Tc/Errors/Types.hs @@ -2924,6 +2924,29 @@ data TcRnMessage where -} TcRnDuplicateMinimalSig :: LSig GhcPs -> LSig GhcPs -> [LSig GhcPs] -> TcRnMessage + {-| TcRnIncompatibleForallVisibility is an error that occurs when + the expected and actual types contain forall-bound variables + that have incompatible visibility or specificity. + + Example: + type family Invis :: Type -> forall a. a + type family Vis :: Type -> forall a -> a + type instance Vis = Invis -- Bad instance + + Test cases: + T18863a + T15079_fail_a + T22648a + T22648b + T22648c + T22648v + T22648v_ql + -} + TcRnIncompatibleForallVisibility + :: TcType + -> TcType + -> TcRnMessage + deriving Generic -- | Things forbidden in @type data@ declarations. @@ -3787,6 +3810,20 @@ data CannotUnifyVariableReason -- type Int, or with a 'TyVarTv'. | DifferentTyVars TyVarInfo | RepresentationalEq TyVarInfo (Maybe CoercibleMsg) + + -- | Can't unify a kind-polymorphic type variable with a type + -- due to visibility difference of forall-bound variables in their kinds. + -- + -- Example: + -- data V k (a :: k) = MkV + -- f :: forall {k} {a :: k} (hk :: forall j. j -> Type). hk a -> () + -- bad_infer = f MkV + -- -- we want to unify hk := V + -- -- but hk :: forall j. j -> Type + -- -- V :: forall k -> k -> Type + -- + -- Test cases: T15079_fail_b T22648v + | ForallKindVisDiff TyVar Type deriving Generic -- | Report a mismatch error without any extra |