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  • Glasgow Haskell CompilerGlasgow Haskell Compiler
  • GHCGHC
  • Issues
  • #1041

Bang patterns in do notation and lambdas

Bang patterns in do-notation and lambdas need parentheses around them to parse. This isn't the case for ~ patterns, or bang patterns in let bindings. Seems like a wibble.

{-# OPTIONS -fbang-patterns #-}

-- doesn't work:        A.hs:5:8: Empty 'do' construct
main1 = do
    !c <- return ()
    return ()

-- doesn't work:        A.hs:12:24: parse error on input `!'
main2 = return () >>= \ !c -> return ()



-- does
main3 = do
    (!c) <- return ()
    return ()

-- does
main4 = return () >>= \ (!c) -> return ()


-- does
main5 = let !x = 1 in return ()


-- does
main6 = do
    ~c <- return ()
    return ()

-- does
main7 = return () >>= \ ~c -> return ()

-- dons

Trac metadata
Trac field Value
Version 6.6
Type Bug
TypeOfFailure OtherFailure
Priority normal
Resolution Unresolved
Component Compiler (Parser)
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system Unknown
Architecture Unknown
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