Aha, that's because `:t` operates on expressions, and when a pattern
synonym is used as an expression the required and provided contexts are
merged into one. Makes sense.
/ Emil
Den 2016-05-26 kl. 20:59, skrev Emil Axelsson:
However, it seems that `:t` gives the wrong type:
*Main> :t AddP
Ah, excellent! Thank you!
However, it seems that `:t` gives the wrong type:
*Main> :t AddP
AddP :: (Num a, Eq a) => Exp a -> Exp a -> Exp a
This type is reported whether or not I include the (correct) signature
for `AddP`.
`:i` is correct though:
*Main> :i AddP
pattern AddP :: () =>
GHC 8.0 swaps the order of provided vs required contexts in a pattern synonym
signature. (7.10 was advertised as experimental). Thus:
pattern AddP :: () => (Num a, Eq a) => Exp a -> Exp a -> Exp a
Then it's fine
Simon
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