Rust: Make path resolution robust against invalid code with conflicting declarations

[hvitved]

Fixes performance on edl-lang/edl, which contains e.g. https://github.com/edl-lang/edl/blob/main/tests/ui/impl-trait/impl-trait-plus-priority.rs.

[Copilot]

Pull request overview

Improves Rust path resolution to remain performant and deterministic in the presence of invalid Rust code that introduces conflicting declarations (e.g., duplicate names), and adds a regression test covering that scenario.

Changes:

• Add an invalid-Rust test case with conflicting struct A declarations and disable cargo check for that fixture.
• Update path resolution to avoid combinatorial blow-ups in invalid code by selecting a single (last) matching child item.
• Update expected test output to reflect the new resolution behavior for the invalid fixture.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
rust/ql/lib/codeql/rust/internal/PathResolution.qll	Adjusts child-successor selection to be robust in invalid/conflicting-declaration scenarios.
rust/ql/test/library-tests/path-resolution/invalid/main.rs	Adds an invalid Rust fixture with conflicting declarations.
rust/ql/test/library-tests/path-resolution/invalid/options.yml	Disables cargo checking for the invalid fixture.
rust/ql/test/library-tests/path-resolution/path-resolution.expected	Updates expected results for the new invalid-code path resolution behavior.

Comments suppressed due to low confidence (1)

rust/ql/test/library-tests/path-resolution/invalid/main.rs:6

• Typo in comment: “precendence” should be “precedence”.

fn f(x: A) {} // $ item=A2 (the later occurence takes precendence)

[Copilot]

Typo in comment: “occurence” should be “occurrence”.

This issue also appears on line 6 of the same file.

Suggested change

	fn f(x: A) {} // $ item=A2 (the later occurence takes precendence)
	fn f(x: A) {} // $ item=A2 (the later occurrence takes precendence)

[Copilot]

Wording in comment: “the later” is ambiguous here; “the latter” better matches the intent (A2 vs A1).

Suggested change

	fn f(x: A) {} // $ item=A2 (the later occurence takes precendence)
	fn f(x: A) {} // $ item=A2 (the latter occurrence takes precedence)

[Copilot]

Grammar in comment: “to safe-guard” should be “to safeguard”.

Suggested change

	// but to safe-guard against combinatorial explosions in invalid code, we always pick the
	// but to safeguard against combinatorial explosions in invalid code, we always pick the