Rust: Take additional type parameter constraints into account

[hvitved]

For example, in

impl<T> SomeType<T> where T: Clone {
    fn foo() where T: Debug { }
}

the constraint Debug additionally applies to T in foo, which was previously not taken into account.

DCA is good; more resolved calls, more alerts, little performance impact.

[Copilot]

Pull request overview

This PR improves Rust call/type resolution by incorporating additional type-parameter constraints introduced on inner items (for example, method-level where clauses) so that these constraints are considered during trait lookup and type inference.

Changes:

• Extend the shared type-inference matching interfaces to allow retrieving type-parameter constraints in a declaration-scoped way.
• Add Rust support for “additional” bounds (derived from constraining items) and thread that context into lookup-trait substitution used by associated-function resolution.
• Update/extend regression and model-generator tests to reflect improved resolution.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
shared/typeinference/codeql/typeinference/internal/TypeInference.qll	Adds a decl-scoped type-parameter constraint accessor and wires it into matching logic.
rust/ql/lib/codeql/rust/internal/typeinference/TypeInference.qll	Incorporates additional per-declaration type-parameter constraints into Rust matching/resolution.
rust/ql/lib/codeql/rust/internal/typeinference/FunctionType.qll	Makes lookup-trait substitution context-aware (AST/item context) to include additional bounds.
rust/ql/lib/codeql/rust/internal/PathResolution.qll	Exposes resolution of additional bounds for type parameters relative to a constraining item.
rust/ql/lib/codeql/rust/elements/internal/TypeParamImpl.qll	Adds API to retrieve additional type bounds applying to a specific constraining item.
rust/ql/test/utils-tests/modelgenerator/option.rs	Updates expected model-generator summary annotations now that resolution improves.
rust/ql/test/library-tests/type-inference/regressions.rs	Adds a regression covering method-level constraints affecting trait method resolution.
rust/ql/test/library-tests/type-inference/type-inference.expected	Updates expected inference results to match improved resolution.