Eta-contraction gives a rather bogus type error message
Consider the following program:
module Main where
type T a = Show a => a
f :: T a -> String
f = showCompiling this with GHC 6.10.3 and -fglasgow-exts gives:
[1 of 1] Compiling Main ( Test.hs, interpreted )
ghc: panic! (the 'impossible' happened)
(GHC version 6.10.3 for i386-apple-darwin):
TcTyFuns.flattenType: unexpected PredTypeTrac metadata
| Trac field | Value |
|---|---|
| Version | 6.10.3 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | Compiler |
| Test case | |
| Differential revisions | |
| BlockedBy | |
| Related | |
| Blocking | |
| CC | thomas@cs.ru.nl |
| Operating system | MacOS X |
| Architecture | x86 |