tcfail042.hs:18:
- No instance for: `Num a'
- arising from an instance declaration, at tcfail042.hs:18
- Available context: (Foo [a])
- From the superclasses of the instance declaration
+ Could not deduce `Num a'
+ (arising from an instance declaration at tcfail042.hs:18)
+ from the context (Eq a, Show a)
+ Probable cause: missing `Num a' in instance declaration context
+ When checking the superclasses of an instance declaration
Compilation had errors