Rust: Implement type inference for trait objects/dyn types
#20084
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Note: The first DCA run showed an increase in type inference inconsistencies. I've fixed those and started a second DCA run. EDIT: The second DCA shows that the type inference inconsistencies are now fixed. The number of type inference inconsistencies now only decreases. |
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geoffw0
reviewed
Jul 23, 2025
geoffw0
approved these changes
Jul 24, 2025
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This PR implements support for trait objects on the form
dyn Trait.The implementation works as follows:
dyn Traitappears somewhere as a declared type then we create aDynTraitTypethat consists of the traitTrait.dyn Traithas a type parameter for every type parameter ofTrait. There is a 1-to-1 correspondence but they're not equal.dyn Traittype is made to implementTraitas if there was animpl<A, B, ...> Trait<A, B, ...> for dyn Trait<A, B, ..>block in the source.Currently the PR doesn't account for the auto traits that one can specify with a
+, for instancedyn Clone + Send + Sync. I don't know if we have a need to consider those, but if we do it should be possible by building on top of the work in this PR.DCA shows a 0.33% point increase in resolved call targets and no change in analysis time.