[GHC] #13018: TH-spliced pattern synonym declaration fails to typecheck
GHC
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Wed Dec 21 23:43:09 UTC 2016
#13018: TH-spliced pattern synonym declaration fails to typecheck
-------------------------------------+-------------------------------------
Reporter: RyanGlScott | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler (Type | Version: 8.0.1
checker) | Keywords:
Resolution: | PatternSynonyms
Operating System: Unknown/Multiple | Architecture:
Type of failure: GHC rejects | Unknown/Multiple
valid program | Test Case:
Blocked By: | Blocking:
Related Tickets: | Differential Rev(s):
Wiki Page: |
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Changes (by RyanGlScott):
* version: 8.1 => 8.0.1
Comment:
It turns out this is a regression, since this program:
{{{#!hs
{-# LANGUAGE GADTs #-}
{-# LANGUAGE PatternSynonyms #-}
{-# LANGUAGE ScopedTypeVariables #-}
module M where
data T a where
MkT :: Eq b => b -> T a
pattern P :: forall b a. b -> T a
pattern P x <- MkT x
}}}
compiles with GHC 7.10.3, but not with GHC 8.0.1, 8.0.2, or HEAD.
--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13018#comment:4>
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