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author | Simon Peyton Jones <simonpj@microsoft.com> | 2018-01-02 17:25:58 +0000 |
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committer | Simon Peyton Jones <simonpj@microsoft.com> | 2018-01-03 11:26:20 +0000 |
commit | 9e5535ca667e060ce1431d42cdfc3a13ae080a88 (patch) | |
tree | a5c4d04e651397eeb059e4a539c57e82f8aab779 /testsuite/tests/typecheck/should_fail/T14607.hs | |
parent | 112266ce62e4fa831b21038be72f8b9ecdf6bfcf (diff) | |
download | haskell-9e5535ca667e060ce1431d42cdfc3a13ae080a88.tar.gz |
Fix OptCoercion
In the presence of -fdefer-type-errors, OptCoercion can
encounter a mal-formed coerercion with type
T a ~ T a b
and that was causing a subsequent Lint error.
This caused Trac #14607. Easily fixed by turning an ASSERT
into a guard.
Diffstat (limited to 'testsuite/tests/typecheck/should_fail/T14607.hs')
-rw-r--r-- | testsuite/tests/typecheck/should_fail/T14607.hs | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/testsuite/tests/typecheck/should_fail/T14607.hs b/testsuite/tests/typecheck/should_fail/T14607.hs new file mode 100644 index 0000000000..891d3ccc18 --- /dev/null +++ b/testsuite/tests/typecheck/should_fail/T14607.hs @@ -0,0 +1,23 @@ +{-# OPTIONS_GHC -fdefer-type-errors #-} + -- This line is crucial to the bug + +{-# Language GADTs #-} +{-# Language InstanceSigs #-} +{-# Language KindSignatures #-} +{-# Language TypeFamilies #-} +{-# Language DataKinds #-} +{-# Language FlexibleInstances #-} + +module T14607 where + +import Data.Kind + +data LamCons :: Type -> Type -> () -> Type where + C :: LamCons a a '() + +class Mk a where + mk :: LamCons a a '() + +instance Mk a where + mk :: LamCons a '() + mk = mk |