Pattern match checker should shortcut on simple cases
I'm autogenerating with TH some code that does a giant string pattern match on up to 60 cases. This match clause includes a default case, but nonetheless I get a warning:
Pattern match checker exceeded (2000000) iterations in
a case alternative. (Use -fmax-pmcheck-iterations=n
to set the maximun number of iterations to n)
Note that in my case all the strings share a great deal in their common prefixes, which probably doesn't help matters.
It seems to me that in a case like this, GHC should be able to just check that there are no duplicate strings (i.e. no overlaps) and that there is a default case (i.e. no incompleteness) rather than running the full checker algo.
I'm not quite sure if there's a good way to generalize such a proposed shortcut so it is not too much of a special case, but likely something could be done?