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Diffstat (limited to 'compiler/typecheck/TcSimplify.hs')
| -rw-r--r-- | compiler/typecheck/TcSimplify.hs | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/compiler/typecheck/TcSimplify.hs b/compiler/typecheck/TcSimplify.hs index bda9b77a9b..838fb78c2e 100644 --- a/compiler/typecheck/TcSimplify.hs +++ b/compiler/typecheck/TcSimplify.hs @@ -152,8 +152,26 @@ solveLocalEqualities :: String -> TcM a -> TcM a solveLocalEqualities callsite thing_inside = do { (wanted, res) <- solveLocalEqualitiesX callsite thing_inside ; emitConstraints wanted + + -- See Note [Fail fast if there are insoluble kind equalities] + ; when (insolubleWC wanted) $ + failM + ; return res } +{- Note [Fail fast if there are insoluble kind equalities] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Rather like in simplifyInfer, fail fast if there is an insoluble +constraint. Otherwise we'll just succeed in kind-checking a nonsense +type, with a cascade of follow-up errors. + +For example polykinds/T12593, T15577, and many others. + +Take care to ensure that you emit the insoluble constraints before +failing, because they are what will ulimately lead to the error +messsage! +-} + solveLocalEqualitiesX :: String -> TcM a -> TcM (WantedConstraints, a) solveLocalEqualitiesX callsite thing_inside = do { traceTc "solveLocalEqualitiesX {" (vcat [ text "Called from" <+> text callsite ]) |