Crash: strange interaction of ScopedTypeVariables extension with type class name resolution
|Reported by:||dominiquedevriese||Owned by:|
|Component:||Compiler (Type checker)||Version:||7.0.4|
|Keywords:||ScopedTypeVariables, type classes||Cc:|
|Type of failure:||Compile-time crash||Test Case:||typecheck/should_fail/T5691|
|Related Tickets:||Differential Rev(s):|
I saw a compiler crash ("the 'impossible' happened..."), seemingly caused by a strange interaction of the ScopedTypeVariables GHC extension with type class name resolution. I am attaching a cut-down example showing the crash. I hope this helps to find the bug. I have only tested with GHC 7.0.4; I am not sure if it is still present in later versions of the compiler. The crash occurs when I load the file in GHCi and evaluate the code
parseRD (pure_ 'a') "a"
or when I simply try to compile the file from the command line.