[Haskell-cafe] out-commented code vs. case with redundant pattern matches

Doug McIlroy doug at cs.dartmouth.edu
Wed Nov 29 13:33:52 UTC 2017

Surely GHC is too clever by half in asserting that just 1 of two
impossible branches is redundant in the code

>     case 0::Int of
>        0 -> putStrLn "A"
>        1 -> putStrLn "B"
>        _ -> putStrLn "C"

The assertion suggests that GHC code optimization would leave
some useless vestige of the third case,

The long-range solution to Thielmann's quandry is a bug report.


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