Representational equalities over AppTys are not hard failures
If I say
module App where
import Data.Coerce
foo :: Coercible (a b) (c d) => a b -> c d
foo = undefined
I get
App.hs:5:8: error:
Couldn't match representation of type ‘a b’ with that of ‘c d’
Inaccessible code in
the type signature for: foo :: Coercible (a b) (c d) => a b -> c d
In the ambiguity check for the type signature for ‘foo’:
foo :: forall (a :: * -> *) b (c :: * -> *) d.
Coercible (a b) (c d) =>
a b -> c d
To defer the ambiguity check to use sites, enable AllowAmbiguousTypes
In the type signature for ‘foo’:
foo :: Coercible (a b) (c d) => a b -> c d
This is very silly, indeed.
Trac metadata
Trac field | Value |
---|---|
Version | 7.11 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |