#13260: panic on unboxed string literal in pattern -------------------------------------+------------------------------------- Reporter: rwbarton | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- I don't think this program is meaningful, but it shouldn't cause a panic. {{{#!hs {-# LANGUAGE MagicHash #-} g y = case y of "a"# -> True _ -> False }}} {{{ [1 of 1] Compiling CaseOnString ( x/CaseOnString.hs, x/CaseOnString.o ) ghc: panic! (the 'impossible' happened) (GHC version 8.0.1 for x86_64-unknown-linux): litValue "a"# }}} The panic is also in at least 7.8, 7.10, and HEAD. `"a"#` has type `Addr#`, and I suppose that if we allow `case` on `Addr#` then it ought to use pointer equality. But the literal `"a"#` has no particular address, so matching against it in a `case` doesn't make sense. So I think we should just disallow unboxed string literals as patterns. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13260 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler