On 6/26/19 9:09 PM, Brandon Allbery wrote:
As of at least recently, empty cases are entirely permitted
Yes I know, but this is not about "empty case" (= no alternative?), but about one (or more) empty alternatives (that are accepted without -XEmptyCase ). I admit it's not related to any practical problem. It came up in the following way: a student who compared ghc's behaviour to that of a purpose-built parser for case expressions that I wrote for my e-Learning/testing system. And I thought - well, the Standard certainly should explain ghc's behaviour, but I have a hard time parsing it. More nit-picking: while "case () of { }" prompts the "Use EmptyCase" hint, "case () of { ; }" is a parse error (no hint), with or without -XEmptyCase. - J