re_rebalance_coherence
The tracking issue for this feature is: #55437
The re_rebalance_coherence feature tweaks the rules regarding which trait
impls are allowed in crates.
The following rule is used:
Given impl<P1..=Pn> Trait<T1..=Tn> for T0, an impl is valid only if at
least one of the following is true:
Traitis a local trait- All of
- At least one of the types
T0..=Tnmust be a local type. LetTibe the first such type. - No uncovered type parameters
P1..=Pnmay appear inT0..Ti(excludingTi)
- At least one of the types
See the RFC for details.