Bogus type error message in type with constraints after the arrow
Hello,
I've found a bug, however it may be a duplicate of one of these: #2846 (closed), #3272 (closed), #3592 (closed), #3125 (closed), #3102 (closed) (roughly in order of duplicate-likelihoodness).
Here's the code:
type Foo a b = () -> (Bar a => a)
class Bar a where {}
foo :: Foo a b
foo = id (undefined :: Foo a b)
And the result of compilation:
$ ghc -fglasgow-exts --make Bug.hs
[1 of 1] Compiling Bug ( Bug.hs, Bug.o )
ghc: panic! (the 'impossible' happened)
(GHC version 6.10.4 for x86_64-unknown-linux):
TcTyFuns.flattenType: unexpected PredType
Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug
I'm running Gentoo Linux, with dev-lang/ghc-6.10.4 (not dev-haskell/haskell-platform)
Linux geneva 2.6.29-gentoo-r5 #1 SMP Sun Jul 12 03:16:58 BST 2009 x86_64 Intel(R) Core(TM)2 CPU 4300 @ 1.80GHz GenuineIntel GNU/Linux
I'm afraid I've not tested this against HEAD, since I couldn't get it to build.
Note that foo = undefined :: Foo a b
does not cause GHC to panic.
Trac metadata
Trac field | Value |
---|---|
Version | 6.10.4 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |