Constructor (de)application as higher precedence than @

@natefaubion

data X = X | Y

ok :: X -> X -> X
ok x@(X) _ = X

err1 :: X -> X -> X
err1 x@X _ = X -- X was given 1 argument but expected 0 arguments

err2 :: X -> X -> X
err2 x@X _ = X -- argument list differs
err2 Y _ = Y

@natefaubion: Yeah, I’d consider that a bug
it treats constructor (de)application as higher precedence than @, which is wrong (edited)

Relates to #3517

~~Matches ghc?~~

Prelude> f x@Just y = y

<interactive>:3:5: error:
    • The constructor ‘Just’ should have 1 argument, but has been given none
    • In the pattern: Just
      In an equation for ‘f’: f x@Just y = y

Edit: never mind, that's definitely wrong, sorry.

Add a test for @-pattern precedence

Add a test for @-pattern precedence (#3631)

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Constructor (de)application as higher precedence than `@` #3532

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Constructor (de)application as higher precedence than @ #3532

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natefaubion commented on Feb 7, 2019

paf31 commented on Feb 7, 2019

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Constructor (de)application as higher precedence than `@` #3532