Suggest ScopedTypeVariables when type variable not in scope
I recently wrote this:
{-# LANGUAGE ExplicitForAll #-}
{-# LANGUAGE TypeApplications #-}
module B where
f :: forall a. a -> a
f x = id @a xAnd was hornswoggled for the better part of five minutes for why "a" wasn't in scope. Answer: you need ScopedTypeVariables. A suggestion would be nice.
Trac metadata
| Trac field | Value |
|---|---|
| Version | 8.0.1 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | Compiler (Type checker) |
| Test case | |
| Differential revisions | |
| BlockedBy | |
| Related | |
| Blocking | |
| CC | goldfire |
| Operating system | |
| Architecture |