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Simon Peyton Jones authored
This patch allows, for the first time, case expressions with an empty list of alternatives. Max suggested the idea, and Trac #6067 showed that it is really quite important. So I've implemented the idea, fixing #6067. Main changes * See Note [Empty case alternatives] in CoreSyn * Various foldr1's become foldrs * IfaceCase does not record the type of the alternatives. I added IfaceECase for empty-alternative cases. * Core Lint does not complain about empty cases * MkCore.castBottomExpr constructs an empty-alternative case expression (case e of ty {}) * CoreToStg converts '(case e of {})' to just 'e'
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