Improve warnings for use of "forall" without -XExistentialQuantification
|Reported by:||dmhouse||Owned by:|
|Type of failure:||None/Unknown||Test Case:|
|Related Tickets:||Differential Rev(s):|
Here's a GHCi session:
Prelude> let foo :: forall a. a; foo = undefined <interactive>:1:19: Illegal operator `.' in type `forall a . a' (Use -XTypeOperators to allow operators in types) Prelude> let foo :: forall a. Show a => a; foo = undefined <interactive>:1:28: parse error on input `=>'
Both of these errors could be improved, I think, by detecting the use of 'forall' as a type variable name, and suggesting -XExistentialQuantification if it's being used.