Add Semigroup warnings
Similar to #8004 (closed), do the following for Semigroup/Monoid:
- Warn when an instance of a class has been given, but the type does not
have a certain superclass instance
- Warn when top-level definitions conflict with future Prelude names
Trac metadata
| Trac field | Value |
|---|---|
| Version | |
| Type | Task |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | Compiler |
| Test case | |
| Differential revisions | |
| BlockedBy | |
| Related | |
| Blocking | |
| CC | hvr |
| Operating system | |
| Architecture |