Constraint synonym instances
It would be great if GHC could compile:
{-# LANGUAGE ConstraintKinds #-}
type Ring = Num
instance Ring [a] where
(+) = (++)
Currently this gives an error: (+)
is not a visible method of class Ring
. After removing the last line, the code compiles with warnings about missing methods.
Trac metadata
Trac field | Value |
---|---|
Version | 7.6.1 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |