Rule matcher failing to look through an imported inlining

Pedro reported

module M1 where
  class MyEnum a where myEnum :: [a]
  instance MyEnum () where myEnum = [()]
 
module M2 where
  import M1

  f1 = map (\() -> 'p') [()]
  f2 = map (\() -> 'q') myEnum

The code for f1 was optimised (by rewrite rules) to

  f1 = ['p']

but the code for f2 wasn't.

Trac metadata

Trac field	Value
Version	7.0.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture