diff options
| author | sheaf <sam.derbyshire@gmail.com> | 2021-08-14 03:41:03 +0200 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2021-08-15 09:00:29 -0400 |
| commit | 1e896b476086e83ed6e97fb9d0ba8b96fed07783 (patch) | |
| tree | 9f55f42c4630878ed94f31ffefa0f8026da8e2b6 /compiler/GHC/HsToCore | |
| parent | a975583c70e57434340d9a20c976c8f06fde9beb (diff) | |
| download | haskell-1e896b476086e83ed6e97fb9d0ba8b96fed07783.tar.gz | |
Detect TypeError when checking for insolubility
We detect insoluble Givens by making getInertInsols
take into account TypeError constraints, on top of insoluble equalities
such as Int ~ Bool (which it already took into account).
This allows pattern matches with insoluble contexts to be reported
as redundant (tyOracle calls tcCheckGivens which calls getInertInsols).
As a bonus, we get to remove a workaround in Data.Typeable.Internal:
we can directly use a NotApplication type family, as opposed to
needing to cook up an insoluble equality constraint.
Fixes #11503 #14141 #16377 #20180
Diffstat (limited to 'compiler/GHC/HsToCore')
| -rw-r--r-- | compiler/GHC/HsToCore/Pmc/Solver.hs | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/compiler/GHC/HsToCore/Pmc/Solver.hs b/compiler/GHC/HsToCore/Pmc/Solver.hs index e0d5c63698..3caced3468 100644 --- a/compiler/GHC/HsToCore/Pmc/Solver.hs +++ b/compiler/GHC/HsToCore/Pmc/Solver.hs @@ -617,6 +617,8 @@ addTyCts nabla@MkNabla{ nabla_ty_st = ty_st } new_ty_cs = do -- | Add some extra type constraints to the 'TyState'; return 'Nothing' if we -- find a contradiction (e.g. @Int ~ Bool@). +-- +-- See Note [Pattern match warnings with insoluble Givens] in GHC.Tc.Solver. tyOracle :: TyState -> Bag PredType -> DsM (Maybe TyState) tyOracle ty_st@(TySt n inert) cts | isEmptyBag cts |