Can't infer Monad n from (Monad m, m ~ n)
This looks like a regression in GHC HEAD.
Test/SmallCheck/Property.hs:187:10:
Could not deduce (Monad n)
arising from the superclasses of an instance declaration
from the context: (Monad m, m ~ n)
bound by the instance declaration
at Test/SmallCheck/Property.hs:187:10-52
Possible fix:
add (Monad n) to the context of the instance declaration
In the instance declaration for ‘Testable n (Property m)’
The code is here: https://github.com/feuerbach/smallcheck/blob/v1.1.1/Test/SmallCheck/Property.hs#L187-L188
Originally reported here: https://github.com/feuerbach/smallcheck/issues/28
Trac metadata
Trac field | Value |
---|---|
Version | 7.11 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler (Type checker) |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |