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).