Rust: Model impl shadowing

rust/ql/lib/codeql/rust/internal/Type.qll

@@ -74,15 +74,31 @@ abstract class Type extends TType {
 abstract private class StructOrEnumType extends Type {
   abstract ItemNode asItemNode();
 
-  final override Function getMethod(string name) {
+  pragma[nomagic]
+  private Function getMethodCand(ImplOrTraitItemNode impl, string name) {
     result = this.asItemNode().getASuccessor(name) and
-    exists(ImplOrTraitItemNode impl | result = impl.getAnAssocItem() |
+    result = impl.getAnAssocItem() and
+    (
       impl instanceof Trait
       or
       impl.(ImplItemNode).isFullyParametric()
     )
   }
 
+  pragma[nomagic]
+  private Function getImplMethod(ImplOrTraitItemNode impl, string name) {
+    result = this.getMethodCand(impl, name) and
+    impl = any(Impl i | not i.hasTrait())
+  }
+
+  final override Function getMethod(string name) {
+    result = this.getImplMethod(_, name)
+    or
+    // methods from `impl` blocks shadow functions from `impl Trait` blocks
+    result = this.getMethodCand(_, name) and
+    not exists(this.getImplMethod(_, name))
+  }
+
   /** Gets all of the fully parametric `impl` blocks that target this type. */
   final override ImplMention getABaseTypeMention() {
     this.asItemNode() = result.resolveSelfTy() and

rust/ql/test/library-tests/type-inference/main.rs

@@ -919,6 +919,33 @@ mod borrowed_typed {
     }
 }
 
+mod impl_overlap {
+    #[derive(Debug)]
+    struct S1;
+
+    trait MyTrait {
+        fn m1(self) -> S1;
+    }
+
+    impl MyTrait for S1 {
+        fn m1(self) -> S1 {
+            panic!("not called");
+        }
+    }
+
+    #[rustfmt::skip]
+    impl S1 {
+        fn m1(self) -> S1 { // target
+            self
+        }
+    }
+
+    pub fn f() {
+        let x = S1;
+        println!("{:?}", x.m1()); // $ method=target
+    }
+}
+
 fn main() {
     field_access::f();
     method_impl::f();
@@ -935,4 +962,5 @@ fn main() {
     trait_implicit_self_borrow::f();
     implicit_self_borrow::f();
     borrowed_typed::f();
+    impl_overlap::f();
 }

rust/ql/test/library-tests/type-inference/type-inference.expected

@@ -1005,7 +1005,17 @@ inferType
 | main.rs:918:15:918:16 | &x |  | file://:0:0:0:0 | & |
 | main.rs:918:15:918:16 | &x | &T | main.rs:894:5:894:13 | S |
 | main.rs:918:16:918:16 | x |  | main.rs:894:5:894:13 | S |
-| main.rs:924:5:924:20 | ...::f(...) |  | main.rs:67:5:67:21 | Foo |
-| main.rs:925:5:925:60 | ...::g(...) |  | main.rs:67:5:67:21 | Foo |
-| main.rs:925:20:925:38 | ...::Foo {...} |  | main.rs:67:5:67:21 | Foo |
-| main.rs:925:41:925:59 | ...::Foo {...} |  | main.rs:67:5:67:21 | Foo |
+| main.rs:927:15:927:18 | SelfParam |  | main.rs:926:5:928:5 | Self [trait MyTrait] |
+| main.rs:931:15:931:18 | SelfParam |  | main.rs:923:5:924:14 | S1 |
+| main.rs:931:27:933:9 | { ... } |  | main.rs:923:5:924:14 | S1 |
+| main.rs:938:15:938:18 | SelfParam |  | main.rs:923:5:924:14 | S1 |
+| main.rs:938:27:940:9 | { ... } |  | main.rs:923:5:924:14 | S1 |
+| main.rs:939:13:939:16 | self |  | main.rs:923:5:924:14 | S1 |
+| main.rs:944:13:944:13 | x |  | main.rs:923:5:924:14 | S1 |
+| main.rs:944:17:944:18 | S1 |  | main.rs:923:5:924:14 | S1 |
+| main.rs:945:26:945:26 | x |  | main.rs:923:5:924:14 | S1 |
+| main.rs:945:26:945:31 | x.m1() |  | main.rs:923:5:924:14 | S1 |
+| main.rs:951:5:951:20 | ...::f(...) |  | main.rs:67:5:67:21 | Foo |
+| main.rs:952:5:952:60 | ...::g(...) |  | main.rs:67:5:67:21 | Foo |
+| main.rs:952:20:952:38 | ...::Foo {...} |  | main.rs:67:5:67:21 | Foo |
+| main.rs:952:41:952:59 | ...::Foo {...} |  | main.rs:67:5:67:21 | Foo |