Rust: Add variables example with let statement in macro

[paldepind]

Adds a variables test with a let statement inside a macro.

The usage of var_in_macro doesn't lead to an instance of VariableAccess. This is because the Variable and VariableAccess instance for var_in_macro doesn't get matched up inside variableReachesCand. I'm guessing this is because the rank calculation uses locations, and the nodes in the expansion of the macro all have the same location.

Copilot reviewed 1 out of 4 changed files in this pull request and generated no comments.

Files not reviewed (3)

• rust/ql/test/library-tests/variables/Cfg.expected: Language not supported
• rust/ql/test/library-tests/variables/Ssa.expected: Language not supported
• rust/ql/test/library-tests/variables/variables.expected: Language not supported

Comments suppressed due to low confidence (1)

rust/ql/test/library-tests/variables/variables.rs:555

• The variable var_in_macro is not being correctly identified for read access within the macro. Ensure that the test framework can handle variable accesses within macro expansions.

let_in_macro!(37); // $ MISSING: read_access=var_in_macro

Tip: If you use Visual Studio Code, you can request a review from Copilot before you push from the "Source Control" tab. Learn more

[hvitved]

I'm guessing this is because the rank calculation uses locations, and the nodes in the expansion of the macro all have the same location.

Sounds reasonable.