Serokell’s Work on GHC: Dependent Types, Part 5

AntC2:

Is there a risk of confusing the kind -> with a ViewPattern?

Yes. Tried initially in 9.10 with no extensions

ghci> let f ((+ 2) -> x) = x in f 7
    Illegal view pattern; suggest enable the extension [correct, same reporting as prev GHCs]

— instead :set -XRequiredTypeArguments; try same input
    error: [GHC-72516] Parse error in pattern: +2

— Ok, :set -XViewPatterns; parsed ok.
— BTW, advance warning:

ghci> let f ((+ 2) -> x :: Int) = x in f 7
    warning: [GHC-00834] …
    * Found an unparenthesized pattern signature …
    * This code might stop working in a future GHC release …

(I was trying to break it :: I wouldn’t usually code that signature like that — yeuch! So I agree with the planned change to the precedence.)