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Diffstat (limited to 'compiler/GHC/Tc/Utils/TcMType.hs')
| -rw-r--r-- | compiler/GHC/Tc/Utils/TcMType.hs | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/compiler/GHC/Tc/Utils/TcMType.hs b/compiler/GHC/Tc/Utils/TcMType.hs index b6f5065997..519a2b37a8 100644 --- a/compiler/GHC/Tc/Utils/TcMType.hs +++ b/compiler/GHC/Tc/Utils/TcMType.hs @@ -1252,6 +1252,9 @@ skolems are in scope within the type itself (e.g. that 'forall arg'). This change is inspired by and described in Section 7.2 of "Kind Inference for Datatypes", POPL'20. +NB: this is all rather similar to, but sadly not the same as + Note [Error on unconstrained meta-variables] + Wrinkle: We must make absolutely sure that alpha indeed is not @@ -1919,6 +1922,9 @@ on kappa. What to do? We choose (D), as described in #17567. Discussion of alternatives is below. +NB: this is all rather similar to, but sadly not the same as + Note [Naughty quantification candidates] + (One last example: type instance F Int = Proxy Any, where the unconstrained kind variable is the inferred kind of Any. The four examples here illustrate all cases in which this Note applies.) @@ -1998,6 +2004,7 @@ doNotQuantifyTyVars :: CandidatesQTvs -> (TidyEnv -> TcM (TidyEnv, SDoc)) -- ^ like "the class context (D a b, E foogle)" -> TcM () +-- See Note [Error on unconstrained meta-variables] doNotQuantifyTyVars dvs where_found | isEmptyCandidates dvs = traceTc "doNotQuantifyTyVars has nothing to error on" empty |