Rust: Path resolution for trait items with default implementations

rust/ql/lib/codeql/rust/elements/internal/PathResolution.qll

@@ -132,8 +132,12 @@ abstract class ItemNode extends AstNode {
     )
     or
     // a trait has access to the associated items of its supertraits
-    result = this.(TraitItemNode).resolveABound().getASuccessorRec(name) and
-    result instanceof AssocItemNode
+    this =
+      any(TraitItemNode trait |
+        result = trait.resolveABound().getASuccessorRec(name) and
+        result instanceof AssocItemNode and
+        not trait.declares(name)
+      )
     or
     // items made available by an implementation where `this` is the implementing type
     exists(ItemNode node |
@@ -141,6 +145,15 @@ abstract class ItemNode extends AstNode {
       result = node.getASuccessorRec(name) and
       result instanceof AssocItemNode
     )
+    or
+    // trait items with default implementations made available in an implementation
+    exists(ImplItemNode impl, ItemNode trait |
+      this = impl and
+      trait = impl.resolveTraitTy() and
+      result = trait.getASuccessorRec(name) and
+      result.(AssocItemNode).hasImplementation() and
+      not impl.declares(name)
+    )
   }
 
   /** Gets a successor named `name` of this item, if any. */
@@ -194,11 +207,16 @@ private class SourceFileItemNode extends ModuleLikeNode, SourceFile {
 }
 
 /** An item that can occur in a trait or an `impl` block. */
-abstract private class AssocItemNode extends ItemNode { }
+abstract private class AssocItemNode extends ItemNode, AssocItem {
+  /** Holds if this associated item has an implementation. */
+  abstract predicate hasImplementation();
+}
 
 private class ConstItemNode extends AssocItemNode instanceof Const {
   override string getName() { result = Const.super.getName().getText() }
 
+  override predicate hasImplementation() { super.hasBody() }
+
   override Namespace getNamespace() { result.isValue() }
 
   override Visibility getVisibility() { result = Const.super.getVisibility() }
@@ -222,9 +240,11 @@ private class VariantItemNode extends ItemNode instanceof Variant {
   override Visibility getVisibility() { result = Variant.super.getVisibility() }
 }
 
-private class FunctionItemNode extends AssocItemNode instanceof Function {
+class FunctionItemNode extends AssocItemNode instanceof Function {
   override string getName() { result = Function.super.getName().getText() }
 
+  override predicate hasImplementation() { super.hasBody() }
+
   override Namespace getNamespace() { result.isValue() }
 
   override Visibility getVisibility() { result = Function.super.getVisibility() }
@@ -245,7 +265,19 @@ abstract private class ImplOrTraitItemNode extends ItemNode {
 }
 
 class ImplItemNode extends ImplOrTraitItemNode instanceof Impl {
-  ItemNode resolveSelfTy() { result = resolvePath(super.getSelfTy().(PathTypeRepr).getPath()) }
+  Path getSelfPath() { result = super.getSelfTy().(PathTypeRepr).getPath() }
+
+  Path getTraitPath() { result = super.getTrait().(PathTypeRepr).getPath() }
+
+  ItemNode resolveSelfTy() { result = resolvePath(this.getSelfPath()) }
+
+  TraitItemNode resolveTraitTy() { result = resolvePath(this.getTraitPath()) }
+
+  /** Holds if this `impl` block declares an associated item named `name`. */
+  pragma[nomagic]
+  predicate declares(string name) {
+    name = super.getAssocItemList().getAnAssocItem().(AssocItemNode).getName()
+  }
 
   override string getName() { result = "(impl)" }
 
@@ -259,6 +291,8 @@ class ImplItemNode extends ImplOrTraitItemNode instanceof Impl {
 private class MacroCallItemNode extends AssocItemNode instanceof MacroCall {
   override string getName() { result = "(macro call)" }
 
+  override predicate hasImplementation() { none() }
+
   override Namespace getNamespace() { none() }
 
   override Visibility getVisibility() { none() }
@@ -293,6 +327,12 @@ class TraitItemNode extends ImplOrTraitItemNode instanceof Trait {
 
   ItemNode resolveABound() { result = resolvePath(this.getABoundPath()) }
 
+  /** Holds if this trait declares an associated item named `name`. */
+  pragma[nomagic]
+  predicate declares(string name) {
+    name = super.getAssocItemList().getAnAssocItem().(AssocItemNode).getName()
+  }
+
   override string getName() { result = Trait.super.getName().getText() }
 
   override Namespace getNamespace() { result.isType() }
@@ -303,6 +343,8 @@ class TraitItemNode extends ImplOrTraitItemNode instanceof Trait {
 class TypeAliasItemNode extends AssocItemNode instanceof TypeAlias {
   override string getName() { result = TypeAlias.super.getName().getText() }
 
+  override predicate hasImplementation() { super.hasTypeRepr() }
+
   override Namespace getNamespace() { result.isType() }
 
   override Visibility getVisibility() { result = TypeAlias.super.getVisibility() }

rust/ql/test/library-tests/path-resolution/main.rs

@@ -430,7 +430,7 @@ mod m16 {
         >::f(&x); // $ MISSING: item=I93
         S::g(&x); // $ item=I92
         x.g(); // $ MISSING: item=I92
-        S::h(&x); // $ MISSING: item=I96
+        S::h(&x); // $ item=I96
         x.h(); // $ MISSING: item=I96
         S::c; // $ item=I95
         <S // $ item=I90

rust/ql/test/library-tests/path-resolution/path-resolution.expected

@@ -187,6 +187,7 @@ resolvePath
 | main.rs:431:9:431:9 | S | main.rs:384:5:384:13 | struct S |
 | main.rs:431:9:431:12 | ...::g | main.rs:397:9:400:9 | fn g |
 | main.rs:433:9:433:9 | S | main.rs:384:5:384:13 | struct S |
+| main.rs:433:9:433:12 | ...::h | main.rs:360:9:363:9 | fn h |
 | main.rs:435:9:435:9 | S | main.rs:384:5:384:13 | struct S |
 | main.rs:435:9:435:12 | ...::c | main.rs:402:9:403:9 | Const |
 | main.rs:436:10:436:10 | S | main.rs:384:5:384:13 | struct S |