#7352: this type signature in a case alternative does not typecheck and requires
ScopedTypeVariables
------------------------------+---------------------------------------------
Reporter: atnnn | Owner: atnnn
Type: bug | Status: new
Priority: normal | Component: Compiler (Type checker)
Version: 7.6.1 | Keywords:
Os: Unknown/Multiple | Architecture: Unknown/Multiple
Failure: None/Unknown | Testcase:
Blockedby: | Blocking:
Related: |
------------------------------+---------------------------------------------
Comment(by atnnn):
Turning on -ddump-tc-trace makes GHC panic on the declaration of E
{{{
{-# LANGUAGE PolyKinds, DataKinds, GADTs #-}
data T a = T
data E a where
E :: T a -> E '[a]
}}}
{{{
tc_lhs_type:
a
Expected kind: k_af0
lk1 a
lk2 a AThing k_aeU
checkExpectedKind
a
k_aeU
Expected kind: k_af0
writeMetaTyVar k_aeY := k_af0
checkExpectedKindghc-stage2: panic! (the 'impossible' happened)
(GHC version 7.7.20121020 for x86_64-unknown-linux):
AThing evaluated unexpectedly tcTyVar a{tv aeN}
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7352#comment:3>
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