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Rust: Rework type inference for impl Trait in return position #19954

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b6d5225
Rust: Add more type inference tests
hvitved Jun 23, 2025
f7195f0
Rust: Handle more explicit type arguments in type inference
hvitved Jun 23, 2025
04bf2f5
Rust: Add more type inference tests
hvitved Jul 2, 2025
b09a778
Rust: Rework type inference for impl Trait in return position
hvitved Jul 2, 2025
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2 changes: 1 addition & 1 deletion rust/ql/lib/codeql/rust/elements/internal/CallImpl.qll
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Original file line number Diff line number Diff line change
Expand Up @@ -78,7 +78,7 @@ module Impl {
}
}

/** Holds if the call expression dispatches to a trait method. */
/** Holds if the call expression dispatches to a method. */
private predicate callIsMethodCall(CallExpr call, Path qualifier, string methodName) {
exists(Path path, Function f |
path = call.getFunction().(PathExpr).getPath() and
Expand Down
24 changes: 17 additions & 7 deletions rust/ql/lib/codeql/rust/internal/PathResolution.qll
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Original file line number Diff line number Diff line change
Expand Up @@ -165,7 +165,8 @@ abstract class ItemNode extends Locatable {
exists(ItemNode node |
this = node.(ImplItemNode).resolveSelfTy() and
result = node.getASuccessorRec(name) and
result instanceof AssocItemNode
result instanceof AssocItemNode and
not result instanceof TypeAlias
)
or
// trait items with default implementations made available in an implementation
Expand All @@ -181,6 +182,10 @@ abstract class ItemNode extends Locatable {
result = this.(TypeParamItemNode).resolveABound().getASuccessorRec(name).(AssocItemNode)
or
result = this.(ImplTraitTypeReprItemNode).resolveABound().getASuccessorRec(name).(AssocItemNode)
or
result = this.(TypeAliasItemNode).resolveAlias().getASuccessorRec(name) and
// type parameters defined in the RHS are not available in the LHS
not result instanceof TypeParam
}

/**
Expand Down Expand Up @@ -289,6 +294,8 @@ abstract class ItemNode extends Locatable {
Location getLocation() { result = super.getLocation() }
}

abstract class TypeItemNode extends ItemNode { }

/** A module or a source file. */
abstract private class ModuleLikeNode extends ItemNode {
/** Gets an item that may refer directly to items defined in this module. */
Expand Down Expand Up @@ -438,7 +445,7 @@ private class ConstItemNode extends AssocItemNode instanceof Const {
override TypeParam getTypeParam(int i) { none() }
}

private class EnumItemNode extends ItemNode instanceof Enum {
private class EnumItemNode extends TypeItemNode instanceof Enum {
override string getName() { result = Enum.super.getName().getText() }

override Namespace getNamespace() { result.isType() }
Expand Down Expand Up @@ -746,7 +753,7 @@ private class ModuleItemNode extends ModuleLikeNode instanceof Module {
}
}

private class StructItemNode extends ItemNode instanceof Struct {
private class StructItemNode extends TypeItemNode instanceof Struct {
override string getName() { result = Struct.super.getName().getText() }

override Namespace getNamespace() {
Expand Down Expand Up @@ -781,7 +788,7 @@ private class StructItemNode extends ItemNode instanceof Struct {
}
}

class TraitItemNode extends ImplOrTraitItemNode instanceof Trait {
class TraitItemNode extends ImplOrTraitItemNode, TypeItemNode instanceof Trait {
pragma[nomagic]
Path getABoundPath() {
result = super.getTypeBoundList().getABound().getTypeRepr().(PathTypeRepr).getPath()
Expand Down Expand Up @@ -838,7 +845,10 @@ class TraitItemNode extends ImplOrTraitItemNode instanceof Trait {
}
}

class TypeAliasItemNode extends AssocItemNode instanceof TypeAlias {
class TypeAliasItemNode extends TypeItemNode, AssocItemNode instanceof TypeAlias {
pragma[nomagic]
ItemNode resolveAlias() { result = resolvePathFull(super.getTypeRepr().(PathTypeRepr).getPath()) }

override string getName() { result = TypeAlias.super.getName().getText() }

override predicate hasImplementation() { super.hasTypeRepr() }
Expand All @@ -854,7 +864,7 @@ class TypeAliasItemNode extends AssocItemNode instanceof TypeAlias {
override string getCanonicalPath(Crate c) { none() }
}

private class UnionItemNode extends ItemNode instanceof Union {
private class UnionItemNode extends TypeItemNode instanceof Union {
override string getName() { result = Union.super.getName().getText() }

override Namespace getNamespace() { result.isType() }
Expand Down Expand Up @@ -912,7 +922,7 @@ private class BlockExprItemNode extends ItemNode instanceof BlockExpr {
override string getCanonicalPath(Crate c) { none() }
}

class TypeParamItemNode extends ItemNode instanceof TypeParam {
class TypeParamItemNode extends TypeItemNode instanceof TypeParam {
private WherePred getAWherePred() {
exists(ItemNode declaringItem |
this = resolveTypeParamPathTypeRepr(result.getTypeRepr()) and
Expand Down
85 changes: 15 additions & 70 deletions rust/ql/lib/codeql/rust/internal/Type.qll
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Original file line number Diff line number Diff line change
Expand Up @@ -15,7 +15,9 @@ newtype TType =
TTrait(Trait t) or
TArrayType() or // todo: add size?
TRefType() or // todo: add mut?
TImplTraitType(ImplTraitTypeRepr impl) or
TImplTraitArgumentType(Function function, ImplTraitTypeRepr impl) {
impl = function.getAParam().getTypeRepr()
} or
TSliceType() or
TTypeParamTypeParameter(TypeParam t) or
TAssociatedTypeTypeParameter(TypeAlias t) { any(TraitItemNode trait).getAnAssocItem() = t } or
Expand Down Expand Up @@ -139,9 +141,6 @@ class TraitType extends Type, TTrait {

override TypeParameter getTypeParameter(int i) {
result = TTypeParamTypeParameter(trait.getGenericParamList().getTypeParam(i))
or
result =
any(AssociatedTypeTypeParameter param | param.getTrait() = trait and param.getIndex() = i)
}

override TypeMention getTypeParameterDefault(int i) {
Expand Down Expand Up @@ -199,53 +198,6 @@ class RefType extends Type, TRefType {
override Location getLocation() { result instanceof EmptyLocation }
}

/**
* An [impl Trait][1] type.
*
* Each syntactic `impl Trait` type gives rise to its own type, even if
* two `impl Trait` types have the same bounds.
*
* [1]: https://doc.rust-lang.org/reference/types/impl-trait.html
*/
class ImplTraitType extends Type, TImplTraitType {
ImplTraitTypeRepr impl;

ImplTraitType() { this = TImplTraitType(impl) }

/** Gets the underlying AST node. */
ImplTraitTypeRepr getImplTraitTypeRepr() { result = impl }

/** Gets the function that this `impl Trait` belongs to. */
abstract Function getFunction();

override StructField getStructField(string name) { none() }

override TupleField getTupleField(int i) { none() }

override TypeParameter getTypeParameter(int i) { none() }

override string toString() { result = impl.toString() }

override Location getLocation() { result = impl.getLocation() }
}

/**
* An [impl Trait in return position][1] type, for example:
*
* ```rust
* fn foo() -> impl Trait
* ```
*
* [1]: https://doc.rust-lang.org/reference/types/impl-trait.html#r-type.impl-trait.return
*/
class ImplTraitReturnType extends ImplTraitType {
private Function function;

ImplTraitReturnType() { impl = function.getRetType().getTypeRepr() }

override Function getFunction() { result = function }
}

/**
* A slice type.
*
Expand Down Expand Up @@ -299,20 +251,6 @@ class TypeParamTypeParameter extends TypeParameter, TTypeParamTypeParameter {
override Location getLocation() { result = typeParam.getLocation() }
}

/**
* Gets the type alias that is the `i`th type parameter of `trait`. Type aliases
* are numbered consecutively but in arbitrary order, starting from the index
* following the last ordinary type parameter.
*/
predicate traitAliasIndex(Trait trait, int i, TypeAlias typeAlias) {
typeAlias =
rank[i + 1 - trait.getNumberOfGenericParams()](TypeAlias alias |
trait.(TraitItemNode).getADescendant() = alias
|
alias order by idOfTypeParameterAstNode(alias)
)
}

/**
* A type parameter corresponding to an associated type in a trait.
*
Expand Down Expand Up @@ -341,8 +279,6 @@ class AssociatedTypeTypeParameter extends TypeParameter, TAssociatedTypeTypePara
/** Gets the trait that contains this associated type declaration. */
TraitItemNode getTrait() { result.getAnAssocItem() = typeAlias }

int getIndex() { traitAliasIndex(_, result, typeAlias) }

override string toString() { result = typeAlias.getName().getText() }

override Location getLocation() { result = typeAlias.getLocation() }
Expand Down Expand Up @@ -405,18 +341,27 @@ class SelfTypeParameter extends TypeParameter, TSelfTypeParameter {
*
* [1]: https://doc.rust-lang.org/reference/types/impl-trait.html#r-type.impl-trait.param
*/
class ImplTraitTypeTypeParameter extends ImplTraitType, TypeParameter {
class ImplTraitArgumentType extends TypeParameter, TImplTraitArgumentType {
private Function function;
private ImplTraitTypeRepr impl;

ImplTraitTypeTypeParameter() { impl = function.getAParam().getTypeRepr() }
ImplTraitArgumentType() { this = TImplTraitArgumentType(function, impl) }

override Function getFunction() { result = function }
/** Gets the function that this `impl Trait` belongs to. */
Function getFunction() { result = function }

/** Gets the underlying AST node. */
ImplTraitTypeRepr getImplTraitTypeRepr() { result = impl }

override StructField getStructField(string name) { none() }

override TupleField getTupleField(int i) { none() }

override TypeParameter getTypeParameter(int i) { none() }

override string toString() { result = impl.toString() }

override Location getLocation() { result = impl.getLocation() }
}

/**
Expand Down
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