
RFC: https://rust-lang.github.io/rfcs/1210-impl-specialization.html
GitHub issue: https://github.com/rust-lang/rust/issues/31844
Update 2026-02-13 (PST) (AI summary of creator comment): The implementation does not have to match the RFC exactly, but negative trait impls alone would not count.
The core requirement is: multiple impls must be allowed as long as they each apply to progressively narrower sets of types.
As a concrete test case: the first AddAssign example in the RFC must be supported by whatever mechanism Rust implements.
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@josh It doesn't have to be exactly this RFC but I think negative trait impls by itself would not count. The core spirit of specialization is being able to have multiple impls as long as they each apply to a narrower and narrower set of types. As a concrete criteria the first AddAssign example in the RFC should be handled which I don't believe can be done with just your mechanism.