Panic; no skolem info (partial type signatures)

This rather minimal program

f :: _ => _f
f = const

results in this:

GHCi, version 7.10.1: http://www.haskell.org/ghc/  :? for help
[1 of 1] Compiling Main             ( Panic.hs, interpreted )

Panic.hs:1:6:
    Found hole ‘_’ with inferred constraints: ()
    To use the inferred type, enable PartialTypeSignatures
    In the type signature for ‘f’: _ => _f

Panic.hs:2:5:
    Couldn't match expected type ‘_f’ with actual type ‘a0 -> b0 -> a0’
      ‘_f’ is untouchable
        inside the constraints ()
        bound by the inferred type of f :: _f
        at Panic.hs:2:1-9ghc: panic! (the 'impossible' happened)
  (GHC version 7.10.1 for x86_64-apple-darwin):
	No skolem info: _f_alF[sk]

The newest open bugs (that reporter could find at the time of reporting) with "no skolem info" in their description are #10404 (closed) and #10432 (closed). The newest bug (which is closed) is #10503 (closed). It seems likely, though, that the above comes from the PartialTypeSignatures implementation (considering the simplicity of the repro).

Trac metadata

Trac field	Value
Version	7.10.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture