Jumbled error message from type family operator

The attached file produces this error message:

Testcase.hs:82:0:
    Couldn't match expected type `True'
           against inferred type `Main.R::<=:GHC6'10GHC6'8 Minor1 minor'
    When generalising the type(s) for `testcase'

That should say

[...] against inferred type `GHC6'10 Minor1 :<=: GHC6'8 minor'

Apologies for the complexity of the testcase; simpler testcases seem to not reproduce the problem.

Trac metadata

Trac field	Value
Version	6.12.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (Type checker)
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