Visible kind applications + data family: `U :: Type' said to be of kind `k0 -> k1` in error message
Using the visible kind applications (D5229) (#12045 (closed)) patch.
GHC erroneously calls U :: Type
a "function" of kind k0 -> k1
if I understand this right,
$ ghci
GHCi, version 8.7.20181017: http://www.haskell.org/ghc/ :? for help
Prelude> :set prompt "> "
> import Data.Kind (Type)
>
> :set -XTypeFamilies
> :set -XTypeApplications
>
> data family U :: Type
> data instance U @Int
<interactive>:7:1: error:
• Cannot apply function of kind ‘k0 -> k1’
to visible kind argument ‘Int’
• In the data instance declaration for ‘U’
>
I expect something like "Cannot apply type U
to visible kind argument Int
" or
> data instance U Int = MkU
<interactive>:7:1: error:
• Expected kind ‘* -> *’, but ‘U’ has kind ‘*’
• In the data instance declaration for ‘U’
>
Trac metadata
Trac field | Value |
---|---|
Version | 8.6.1 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |