infix assert panics ghc
I was repeatedly getting this:
ghc-6.8.3: panic! (the 'impossible' happened)
(GHC version 6.8.3 for i386-unknown-linux):
rename/RnExpr.lhs:(139,26)-(150,42): Non-exhaustive patterns in lambda
After some narrowing down, I eventually found the culprit and got a repeatable error with this minimal snippet:
import Control.Exception (assert)
foo = True `assert` ()
The infixness is crucial; assert True ()
compiles without difficulty. I use infix notation elsewhere, so it appears to be something special about assert
.
I was able to compile successfully if I used -O2
. I see now that was likely because the asserts are simply eliminated early.
I compiled ghc from sources, so it's barely possible I did something wrong there, but the nature of the symptoms make this doubtful.
Trac metadata
Trac field | Value |
---|---|
Version | 6.8.3 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |