• Simon Peyton Jones's avatar
    Fix combineIdenticalAlts · 514bac26
    Simon Peyton Jones authored
    This long-standing bug in CoreUtils.combineIdenticalAlts
    was shown up by Trac #11172. The effect was that it returned
    a correct set of alternatives, but a bogus set of "impossible
    default constructors".  That meant that we subsequently
    removed all the alternatives from a case, and hence ended
    up with a bogusly empty case that should not have been empty.
    
    See Note [Care with impossible-constructors when
    combining alternatives] in CoreUtils.
    514bac26
T11172.hs 1.34 KB