GHC panic: boxy_match_s
I get, in two different modules in the same 100+ module project (different dependency ordering by ghc --make for different executables):
ghc: panic! (the 'impossible' happened)
(GHC version 6.10.4 for powerpc-unknown-linux):
boxy_match_s
I found boxy_match_s
as auxiliary function of boxyMatchTypes
in compiler/typecheck/TcUnify.lhs
, but, using
find . -type f | xargs grep -n boxyMatchTypes /dev/null
, could not even find a call site of boxyMatchTypes
!
The LANGUAGE pragmas of the two modules:
{-# LANGUAGE DeriveDataTypeable, FlexibleContexts,
MultiParamTypeClasses, FlexibleInstances
#-}
{-# LANGUAGE ScopedTypeVariables,
MultiParamTypeClasses, FunctionalDependencies, FlexibleInstances
#-}
(I do not consciously use impredicative types anywhere.)
This occurred after I added additional type parameters (without fundeps) to intermediate type classes (with other fundeps) in larger class hierarchies, and performed lots of related changes.
(make clean
does not help.)
Hoping that just the knowledge that this can happen leads to a fix...
Wolfram
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 |