Poor error message for unbound variable in pattern synonym

When I say

pattern OneElt = [x]

I get

    Right-hand side of bidirectional pattern synonym cannot be used as an expression
      [x]

I have two complaints with this error message:

1. It's very unclear what's actually wrong with the pattern -- [x] looks like a perfectly fine expression, until I realize that x is unbound.
2. The herald of the error is more than 80 characters (if you count the indentation) and wraps on my 80-character terminal. GHC tends to avoid this elsewhere, and so the wrapping is suboptimal.

I would easily say that issue (1) is more important than issue (2).

Perhaps this would be better:

    Variable `x' is unbound in the bidirectional pattern synonym `OneElt':
      [x]

Trac metadata

Trac field	Value
Version	7.9
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture