Unlifted types and pattern synonym signatures

The following program is rejected by ghc-8.0.1:

{-# LANGUAGE MagicHash #-}
{-# LANGUAGE PatternSynonyms #-}
module Foo where

import GHC.Exts (Int#)

pattern Zero :: Int# -- commenting out this line works
pattern Zero <- 0#

% ghc-stage2 unlifted-pattern-synonym.hs
[1 of 1] Compiling Foo              ( unlifted-pattern-synonym.hs, unlifted-pattern-synonym.o )

unlifted-pattern-synonym.hs:7:17: error:
    • Expecting a lifted type, but ‘Int#’ is unlifted
    • In the type ‘Int#’

Commenting out the type signature removes the error.

GHC 7.10.3 accepts this program, with and without the type signature.

Trac metadata

Trac field	Value
Version	8.0.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (Type checker)
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