#14569: refutable let bindings produce "irrefutable pattern failed" errors -------------------------------------+------------------------------------- Reporter: int-e | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.2.1 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Poor/confusing Unknown/Multiple | error message Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- In ghc-8.2.2 (probably since ghc-8.0.1), strict pattern matches in let bindings produce "Irrefutable pattern failed" errors. {{{#!hs GHCi, version 8.2.2: http://www.haskell.org/ghc/ :? for help Prelude> :set -XBangPatterns Prelude> let ![] = [1] in 1 *** Exception: <interactive>:2:5-13: Irrefutable pattern failed for pattern [] }}} In ghc-7.10.2, normal pattern match failures were produced. {{{#!hs GHCi, version 7.10.2: http://www.haskell.org/ghc/ :? for help Prelude> :set -XBangPatterns Prelude> let ![] = [1] in 1 *** Exception: <interactive>:3:5-13: Non-exhaustive patterns in pattern binding }}} To my mind, the latter error makes much more sense; the effect of the ! is to make the pattern an ordinary, refutable one. Could the old behavior be restored? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14569 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler