Type synonym referred to as datatype in error message
To reproduce the issue, compile this file with GHC 8.0.1, 8.0.2, 8.2.1, or HEAD:
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE RankNTypes #-}
module Bug where
import Data.Proxy
type Wat = forall (a :: k). Proxy a
GHCi, version 8.3.20170706: http://www.haskell.org/ghc/ :? for help
Loaded GHCi configuration from /home/rgscott/.ghci
[1 of 1] Compiling Bug ( Bug.hs, interpreted )
Bug.hs:7:1: error:
• Kind variable ‘k’ is implicitly bound in datatype
‘Wat’, but does not appear as the kind of any
of its type variables. Perhaps you meant
to bind it (with TypeInType) explicitly somewhere?
Type variables with inferred kinds: (k :: *)
• In the type declaration for ‘Wat’
|
7 | type Wat = forall (a :: k). Proxy a
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The error message mistakenly refers to Wat
as a datatype.
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 | |
Operating system | |
Architecture |