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  • Glasgow Haskell CompilerGlasgow Haskell Compiler
  • GHCGHC
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  • #15852
Closed
Open
Issue created Nov 02, 2018 by Richard Eisenberg@raeDeveloper

Bad axiom produced for polykinded data family

When I say

data family DF a (b :: k)
data instance DF (Proxy c) :: Proxy j -> Type

with -ddump-tc, I get

  axiom Scratch.D:R:DFProxyProxy0 ::
    forall k1 k2 (c :: k1) (j :: k2) (a :: Proxy j).
      DF (Proxy c) a = Scratch.R:DFProxyProxy k1 k2 c j

This is bogus, because a should be on the RHS, too. It's not clear to me whether this is a pretty-printing bug or a real one.

Trac metadata
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Version 8.7
Type Bug
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component Compiler
Test case
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