Code using ConstraintKinds needs explicit kind signature with GHC 8.2.1
The attached module compiles without errors with GHC 8.0.1 but needs an explicit kind signature with GHC 8.2.1-rc2.
Mentioned in this ghc-dev thread.
Compiling the attached file fails gives the error:
[[1 of 1] Compiling CKBug ( CKBug.hs, interpreted )
CKBug.hs:33:4: error:
• Expected a type, but
‘(PropagIOConstraint l a,
Missing (PropagIOVector l) (PropagIONullable l a),
Elem (PropagIONullable l a) ~ a)’ has kind
‘Constraint’
• In the type ‘((PropagIOConstraint l a,
Missing (PropagIOVector l) (PropagIONullable l a),
Elem (PropagIONullable l a) ~ a))’
In the type declaration for ‘CanSerialize’
|
33 | (( PropagIOConstraint l a
| ^^^^^^^^^^^^^^^^^^^^^^^^...
CKBug.hs:42:4: error:
• Expected a constraint,
but ‘(CanSerialize l Double, CanSerialize l Int)’ has kind ‘*’
• In the type ‘(CanSerialize l Double, CanSerialize l Int)’
In the type declaration for ‘CanSerializePropagTypes’
|
42 | ( CanSerialize l Double
| ^^^^^^^^^^^^^^^^^^^^^^^...