Rust: Improve handling of where clauses in type inference and path resolution

[hvitved]

A rebased version of #20140.

[Copilot]

Pull Request Overview

This PR improves the handling of where clauses in Rust type inference and path resolution. It enhances CodeQL's ability to understand type bounds defined in where clauses, particularly for type parameters and traits, improving the accuracy of type inference and path resolution.

• Adds support for where clauses on type parameters and traits
• Improves type bound resolution in both direct and where clause contexts
• Updates test cases to cover more complex where clause scenarios

Reviewed Changes

Copilot reviewed 9 out of 10 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
rust/ql/test/library-tests/type-inference/main.rs	Adds comprehensive test cases for where clause scenarios including trait bounds
rust/ql/test/library-tests/path-resolution/main.rs	Adds test for where clause with Self and type parameters
rust/ql/lib/codeql/rust/elements/internal/TypeParamImpl.qll	Implements getATypeBound() to collect bounds from direct and where clauses
rust/ql/lib/codeql/rust/elements/internal/TraitImpl.qll	Implements getATypeBound() for traits with where clause support
rust/ql/lib/codeql/rust/internal/TypeInference.qll	Updates to use new getATypeBound() methods
rust/ql/lib/codeql/rust/internal/PathResolution.qll	Simplifies bound path resolution using new methods

[Copilot]

The logic in the second disjunct doesn't guarantee that the WherePred wp from getAWherePred() is the same as the one retrieved from getPredicate(i). This could lead to incorrect indexing. Consider explicitly linking the where predicate to its index in the where clause.

Suggested change

	wp = any(WhereClause wc).getPredicate(i)
	exists(WhereClause wc, WherePred wp |
	wp = wc.getPredicate(i) and
	wp = this.(TypeParamItemNode).getAWherePred() and
	tbl = wp.getTypeBoundList()

[Copilot]

The string comparison getText() = \"Self\" is fragile and may not handle all cases where Self is referenced. Consider using a more robust type-based comparison or path resolution to identify Self references.

Suggested change

	wp.getTypeRepr().(PathTypeRepr).getPath().getText() = "Self" and
	isSelfPath(wp.getTypeRepr().(PathTypeRepr).getPath()) and

[geoffw0]

Thanks for doing this.

The analysis time regression seems to have mostly gone away with the rebase (which was expected). 👍