Obscure warning: Var/Type length mismatch when using GADTs and TypeFamilies

GHC 7.4.2 and 7.6.1 both write obscure warning without any link to source line:

$ ghc --make test.hs
[1 of 1] Compiling Main             ( test.hs, test.o )
Var/Type length mismatch: 
    []
    [main:Main.Credit{tc ra2}]
Var/Type length mismatch: 
    []
    [main:Main.Debit{tc ra1}]
Linking test ...

Near to minimal example (my real program is quite big and uses GHC type system a lot): http://hpaste.org/78958

GHC 7.4.2 output: http://hpaste.org/78959

GHC 7.6.1 output: http://hpaste.org/78961

Trac metadata

Trac field	Value
Version	7.6.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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