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Rust: Small refactor in TypeMention.qll #21422

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4 changes: 2 additions & 2 deletions rust/ql/lib/codeql/rust/internal/typeinference/AssociatedType.qll
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Original file line number Diff line number Diff line change
Expand Up @@ -39,8 +39,8 @@ predicate pathTypeAsTraitAssoc(
/**
* Holds if `assoc` is accessed on `tp` in `path`.
*
* That is, this is the case when `path` is of the form `<tp as
* Trait>::AssocType` or `tp::AssocType`; and `AssocType` resolves to `assoc`.
* That is, this is the case when `path` is of the form `<tp as Trait>::AssocType`
* or `tp::AssocType`; and `AssocType` resolves to `assoc`.
*/
predicate tpAssociatedType(TypeParam tp, AssocType assoc, Path path) {
resolvePath(path.getQualifier()) = tp and
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43 changes: 26 additions & 17 deletions rust/ql/lib/codeql/rust/internal/typeinference/TypeMention.qll
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Original file line number Diff line number Diff line change
Expand Up @@ -699,9 +699,13 @@ class PreTypeMention = PreTypeMention::TypeMention;
/**
* Holds if `path` accesses an associated type `alias` from `trait` on a
* concrete type given by `tm`.
*
* `implOrTmTrait` is either the mention that resolves to `trait` when `path`
* is of the form `<Type as Trait>::AssocType`, or the enclosing `impl` block
* when `path` is of the form `Self::AssocType`.
Comment on lines +703 to +705
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Copilot AI Mar 6, 2026

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The doc comment describes implOrTmTrait as a “mention”, but the parameter is typed as AstNode and is used as either an Impl node or the trait PathTypeRepr from <Type as Trait>::.... Consider rewording to explicitly mention the concrete AST node kinds (e.g., Impl vs trait PathTypeRepr) to avoid confusion for readers.

Suggested change
* `implOrTmTrait` is either the mention that resolves to `trait` when `path`
* is of the form `<Type as Trait>::AssocType`, or the enclosing `impl` block
* when `path` is of the form `Self::AssocType`.
* `implOrTmTrait` is the AST node corresponding to the trait in the context of
* the access: it is either the trait `PathTypeRepr` from a path of the form
* `<Type as Trait>::AssocType`, or the enclosing `Impl` node when `path` is of
* the form `Self::AssocType`.

Copilot uses AI. Check for mistakes.
*/
private predicate pathConcreteTypeAssocType(
Path path, PreTypeMention tm, TraitItemNode trait, PreTypeMention tmTrait, TypeAlias alias
Path path, PreTypeMention tm, TraitItemNode trait, AstNode implOrTmTrait, TypeAlias alias
) {
exists(Path qualifier |
qualifier = path.getQualifier() and
Expand All @@ -710,19 +714,19 @@ private predicate pathConcreteTypeAssocType(
// path of the form `<Type as Trait>::AssocType`
// ^^^ tm ^^^^^^^^^ name
exists(string name |
pathTypeAsTraitAssoc(path, tm, tmTrait, trait, name) and
pathTypeAsTraitAssoc(path, tm, implOrTmTrait, trait, name) and
getTraitAssocType(trait, name) = alias
)
or
// path of the form `Self::AssocType` within an `impl` block
// tm ^^^^ ^^^^^^^^^ name
exists(ImplItemNode impl |
alias = resolvePath(path) and
qualifier = impl.getASelfPath() and
tm = impl.(Impl).getSelfTy() and
trait.getAnAssocItem() = alias and
tmTrait = impl.getTraitPath()
)
implOrTmTrait =
any(ImplItemNode impl |
alias = resolvePath(path) and
qualifier = impl.getASelfPath() and
tm = impl.(Impl).getSelfTy() and
trait.getAnAssocItem() = alias
)
)
}

Expand All @@ -741,21 +745,26 @@ private module PathSatisfiesConstraint =
*/
private Type getPathConcreteAssocTypeAt(Path path, TypePath typePath) {
exists(
PreTypeMention tm, ImplItemNode impl, TraitItemNode trait, TraitType t, PreTypeMention tmTrait,
PreTypeMention tm, ImplItemNode impl, TraitItemNode trait, TraitType t, AstNode implOrTmTrait,
TypeAlias alias, TypePath path0
|
pathConcreteTypeAssocType(path, tm, trait, tmTrait, alias) and
pathConcreteTypeAssocType(path, tm, trait, implOrTmTrait, alias) and
t = TTrait(trait) and
PathSatisfiesConstraint::satisfiesConstraintTypeThrough(tm, impl, t, path0, result) and
path0.isCons(TAssociatedTypeTypeParameter(trait, alias), typePath)
|
tmTrait.getTypeAt(TypePath::nil()) != t
implOrTmTrait instanceof Impl
or
not exists(TypePath path1, Type t1 |
t1 = impl.getTraitPath().(PreTypeMention).getTypeAt(path1) and
not t1 instanceof TypeParameter and
t1 != tmTrait.getTypeAt(path1)
)
// When `path` is of the form `<Type as Trait>::AssocType` we need to check
// that `impl` is not more specific than the mentioned trait
implOrTmTrait =
any(PreTypeMention tmTrait |
not exists(TypePath path1, Type t1 |
t1 = impl.getTraitPath().(PreTypeMention).getTypeAt(path1) and
not t1 instanceof TypeParameter and
t1 != tmTrait.getTypeAt(path1)
)
)
)
}

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