Rust: extract generic parameters, arguments and resolve bound type variables

[aibaars]

This PR aims to support the extraction of generic parameters, arguments, and the resolution of bound type variables in Rust.

[Copilot]

Pull Request Overview

This PR aims to support the extraction of generic parameters, arguments, and the resolution of bound type variables in Rust. It introduces two new generic structs (LocalKey and Thing) and implements a From trait conversion for Thing instantiated with type X.

Files not reviewed (3)

• rust/ql/lib/codeql/rust/elements/internal/LifetimeImpl.qll: Language not supported
• rust/ql/test/extractor-tests/crate_graph/modules.expected: Language not supported
• rust/ql/test/extractor-tests/crate_graph/modules.ql: Language not supported

Comments suppressed due to low confidence (2)

rust/ql/test/extractor-tests/crate_graph/module.rs:47

• [nitpick] The struct name 'LocalKey' is ambiguous; consider renaming it or adding a doc comment to clarify its purpose.

pub struct LocalKey<T: 'static> {

rust/ql/test/extractor-tests/crate_graph/module.rs:48

• [nitpick] Consider renaming the field 'inner' to a more descriptive name that reflects its functionality to improve code readability.

    inner: fn(Option<&mut Option<T>>) -> *const T,

[redsun82]

I'll dive into it more in depth tomorrow, but a generic comment I have is that crate_graph.rs is growing even more in complexity, and as far as I can tell it's really using very unstable parts of rust-analyzer. In my rust-analyzer updates experiences, this is the code that has been breaking on every update and needs quite some effort to keep up to date (see the next update in the queue).

That said, is that something we can conceivably avoid? Is running some limited form of the regular generated extractor on dependency source out of the question because of performance? I'm starting to fear this code is creeping out of control a bit, and risks becoming the biggest maintenance burden of the whole extractor.

[redsun82]

Hoestly did not have a deep look at the new crate graph code, but we can work on that in the next days.