Bad error message when unidirectional pattern synonym used in bidirectional pattern synonym
If I write:
{-# LANGUAGE PatternSynonyms #-}
module I where
pattern P2 x y <- (x, y)
pattern P1 x y = P2 x y
I get the error:
ezyang@sabre:~$ ghc-8.0 -c I.hs
I.hs:5:18: error:
• non-bidirectional pattern synonym ‘P2’ used in an expression
• In the expression: P2 x y
In an equation for ‘$bP1’: $bP1 x y = P2 x y
Trac metadata
Trac field | Value |
---|---|
Version | 8.0.1 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | low |
Resolution | Unresolved |
Component | Compiler (Type checker) |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |