Rust: Implement type inference for ref expression as type equality #19724
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Pull Request Overview
This PR enhances Rust expression type inference by treating &x as a true type equality and removes legacy reference-handling logic. Key changes include:
- Added new test cases in
main.rsto verify boolean and custom-flag type inference through multiple borrows. - Extended the
typeEqualitypredicate to includeRefExprand simplifiedinferRefExprTypein QL. - Removed outdated logic for reference-expression inference in
TypeInference.qll.
Reviewed Changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
| rust/ql/test/library-tests/type-inference/main.rs | Added MyFlag struct tests and **&&true inference |
| rust/ql/lib/codeql/rust/internal/TypeInference.qll | Updated typeEquality, simplified inferRefExprType and inference pipeline |
Comments suppressed due to low confidence (2)
rust/ql/test/library-tests/type-inference/main.rs:1158
- [nitpick] The field name
boolshadows the built-in type name and may be confusing; consider renaming it to something more descriptive likeflagorstate.
struct MyFlag {
rust/ql/lib/codeql/rust/internal/TypeInference.qll:980
- [nitpick] Update this doc comment to mention that
inferRefExprTypeno longer takes apathparameter and now only returnsTRefTypefor the givenRefExpr.
/** Gets the root type of the reference expression `re`. */
hvitved
approved these changes
Jun 11, 2025
|
DCA seems fine. Overall a reduction in missing call targets. |
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I was debugging an issue where types where not inferred correctly, and realized that for a call like
f(&a)the declared type offs first parameters would not flow toathrough the borrow.This PR fixes that and also removes some logic for ref expressions that doesn't match Rust's type system. Due to implicit dereferencing
&&&&aand&acan seem interchangeable, but the types are distinct. Removing this collapsing doesn't seem to affect the tests.