Ticket #5970 (closed bug: wontfix)
Type checker hangs
When compiling my synthesizer-llvm package, GHC-7.4.1 hangs in the type checking phase for the module http://code.haskell.org/synthesizer/llvm/src/Synthesizer/LLVM/Server/Packed/Instrument.hs
This module always needed more than a minute for type-checking in GHC-7.2.2 and before. I guess this was because it is a module where functions with a lot of type-level arithmetic from the type-level package are applied to values of concrete types. Maybe with GHC-7.4.1 the compilation time simply became even longer - at least several minutes.
I tried to simplify the example and reduce the dependencies. This is not so simple because reducing the module size also decreases type checking time and when drastically simplified the compilation time for that module is ok. Now I am trying to construct an example where I repeat the same (simple) function definition. I already observed that repeating a function definition n times does not multiply the type checking by n but it needs considerably more time. I think this can be considered a bug.
I am investigating further. If you have some advice, I like to know. Maybe you remember a 'foldl' that should be a 'foldr' in the type checker, that may cause a quadratic type checking time ... If so then this would be a good opportunity to fix it. ;-)