Ticket #5929 (closed bug: fixed)
Exciting arity warning when compiling with optimizations
When trying to compile a file generated by UUAG ( http://www.cs.uu.nl/wiki/HUT/AttributeGrammarSystem) using optimizations on GHC 7.2.1 (Windows), 7.2.2 (Mac) or 7.4.1 (Windows) I get a line that says only "Exciting arity" followed by some GHC internal code (maybe GHC Core?).
The code still compiles and executes as expected, however this warning clearly indicates that something (either in the code or in ghc) is not working as expected.
Changing the code sometimes eliminates that warning, sometimes it doesn't. The version attached was the smallest I could get that still got me the warnings (and does not depend on any 3rd party libraries, if anyone's interested in reproducing it).