Check if constraint synonym satisfies functional dependencies
When we resolve #12679 (closed), it will be possible to implement an abstract type class using a constraint synonym. However, in my implementation, I didn't implement functional dependency checking:
signature H where
class F a b | a -> b
-- This should be an invalid implementation
module H where
type F a b = (Eq a, Eq b)The check is annoying fiddly: we have to descend into the constraint synonym, collect all the implied fundeps, and then see if we have the ones we need, so I didn't implement it. Maybe some time.
Trac metadata
| Trac field | Value |
|---|---|
| Version | 8.1 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | low |
| Resolution | Unresolved |
| Component | Compiler (Type checker) |
| Test case | |
| Differential revisions | |
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| Related | |
| Blocking | |
| CC | |
| Operating system | |
| Architecture |