OccurAnal fails to rediscover join points
Ben writes: I've noticed that a new WARN in OccurAnal seems to be quite loud. Validations now produce thousands of lines of the form,
WARNING: file compiler/simplCore/OccurAnal.hs, line 2633
OccurAnal failed to rediscover join point(s): [$j_shTG]
WARNING: file compiler/simplCore/OccurAnal.hs, line 2633
OccurAnal failed to rediscover join point(s): [$w$j_sl22]
WARNING: file compiler/simplCore/OccurAnal.hs, line 2633
OccurAnal failed to rediscover join point(s): [$w$j_sl1W]
WARNING: file compiler/simplCore/OccurAnal.hs, line 2633
OccurAnal failed to rediscover join point(s): [$w$j_sl1Q]
It is not clear why the warning from OccurAnal
about rediscovering join points is ever firing. There's one circumstance I can think of, namely the special typing rule allowing jumps from β-redexes, but the warning fires repeatedly and β-redexes don't survive the simplifier.
This isn't hard evidence of something wrong, but it is deeply suspicious.