Rust: Type inference for impl trait types with type parameters

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

@@ -1,17 +1,18 @@
-// generated by codegen, remove this comment if you wish to edit this file
 /**
  * This module provides a hand-modifiable wrapper around the generated class `ImplTraitTypeRepr`.
  *
  * INTERNAL: Do not use.
  */
 
 private import codeql.rust.elements.internal.generated.ImplTraitTypeRepr
+private import rust
 
 /**
  * INTERNAL: This module contains the customizable definition of `ImplTraitTypeRepr` and should not
  * be referenced directly.
  */
 module Impl {
+  // the following QLdoc is generated: if you need to edit it, do it in the schema file
   /**
    * An `impl Trait` type.
    *
@@ -21,5 +22,15 @@ module Impl {
    * //          ^^^^^^^^^^^^^^^^^^^^^^^^^^
    * ```
    */
-  class ImplTraitTypeRepr extends Generated::ImplTraitTypeRepr { }
+  class ImplTraitTypeRepr extends Generated::ImplTraitTypeRepr {
+    /** Gets the function for which this impl trait type occurs, if any. */
+    Function getFunction() {
+      this.getParentNode*() = [result.getRetType().getTypeRepr(), result.getAParam().getTypeRepr()]
+    }
+
+    /** Holds if this impl trait type occurs in the return type of a function. */
+    predicate isInReturnPos() {
+      this.getParentNode*() = this.getFunction().getRetType().getTypeRepr()
+    }
+  }
 }

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

@@ -52,10 +52,21 @@ newtype TType =
   TAssociatedTypeTypeParameter(TypeAlias t) { any(TraitItemNode trait).getAnAssocItem() = t } or
   TArrayTypeParameter() or
   TDynTraitTypeParameter(AstNode n) { dynTraitTypeParameter(_, n) } or
+  TImplTraitTypeParameter(ImplTraitTypeRepr implTrait, TypeParam tp) {
+    implTraitTypeParam(implTrait, _, tp)
+  } or
   TRefTypeParameter() or
   TSelfTypeParameter(Trait t) or
   TSliceTypeParameter()
 
+predicate implTraitTypeParam(ImplTraitTypeRepr implTrait, int i, TypeParam tp) {
+  implTrait.isInReturnPos() and
+  tp = implTrait.getFunction().getGenericParamList().getTypeParam(i) and
+  // Only include type parameters of the function that occur inside the impl
+  // trait type.
+  exists(Path path | path.getParentNode*() = implTrait and resolvePath(path) = tp)
+}
+
 /**
  * A type without type arguments.
  *
@@ -263,7 +274,12 @@ class ImplTraitType extends Type, TImplTraitType {
 
   override TupleField getTupleField(int i) { none() }
 
-  override TypeParameter getTypeParameter(int i) { none() }
+  override TypeParameter getTypeParameter(int i) {
+    exists(TypeParam tp |
+      implTraitTypeParam(impl, i, tp) and
+      result = TImplTraitTypeParameter(impl, tp)
+    )
+  }
 
   override string toString() { result = impl.toString() }
 
@@ -302,7 +318,7 @@ class DynTraitType extends Type, TDynTraitType {
 class ImplTraitReturnType extends ImplTraitType {
   private Function function;
 
-  ImplTraitReturnType() { impl = function.getRetType().getTypeRepr() }
+  ImplTraitReturnType() { impl.isInReturnPos() and function = impl.getFunction() }
 
   override Function getFunction() { result = function }
 }
@@ -456,6 +472,21 @@ class DynTraitTypeParameter extends TypeParameter, TDynTraitTypeParameter {
   override Location getLocation() { result = n.getLocation() }
 }
 
+class ImplTraitTypeParameter extends TypeParameter, TImplTraitTypeParameter {
+  private TypeParam typeParam;
+  private ImplTraitTypeRepr implTrait;
+
+  ImplTraitTypeParameter() { this = TImplTraitTypeParameter(implTrait, typeParam) }
+
+  TypeParam getTypeParam() { result = typeParam }
+
+  ImplTraitTypeRepr getImplTraitTypeRepr() { result = implTrait }
+
+  override string toString() { result = "impl(" + typeParam.toString() + ")" }
+
+  override Location getLocation() { result = typeParam.getLocation() }
+}
+
 /** An implicit reference type parameter. */
 class RefTypeParameter extends TypeParameter, TRefTypeParameter {
   override string toString() { result = "&T" }
@@ -569,5 +600,7 @@ final class SelfTypeBoundTypeAbstraction extends TypeAbstraction, Name {
 }
 
 final class ImplTraitTypeReprAbstraction extends TypeAbstraction, ImplTraitTypeRepr {
-  override TypeParameter getATypeParameter() { none() }
+  override TypeParameter getATypeParameter() {
+    implTraitTypeParam(this, _, result.(TypeParamTypeParameter).getTypeParam())
+  }
 }

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

@@ -83,42 +83,48 @@ private module Input1 implements InputSig1<Location> {
 
   int getTypeParameterId(TypeParameter tp) {
     tp =
-      rank[result](TypeParameter tp0, int kind, int id |
+      rank[result](TypeParameter tp0, int kind, int id1, int id2 |
         tp0 instanceof ArrayTypeParameter and
         kind = 0 and
-        id = 0
+        id1 = 0 and
+        id2 = 0
         or
         tp0 instanceof RefTypeParameter and
         kind = 0 and
-        id = 1
+        id1 = 0 and
+        id2 = 1
         or
         tp0 instanceof SliceTypeParameter and
         kind = 0 and
-        id = 2
+        id1 = 0 and
+        id2 = 2
         or
         kind = 1 and
-        id =
+        id1 = 0 and
+        id2 =
           idOfTypeParameterAstNode([
               tp0.(DynTraitTypeParameter).getTypeParam().(AstNode),
               tp0.(DynTraitTypeParameter).getTypeAlias()
             ])
         or
         kind = 2 and
-        exists(AstNode node | id = idOfTypeParameterAstNode(node) |
+        id1 = idOfTypeParameterAstNode(tp0.(ImplTraitTypeParameter).getImplTraitTypeRepr()) and
+        id2 = idOfTypeParameterAstNode(tp0.(ImplTraitTypeParameter).getTypeParam())
+        or
+        kind = 3 and
+        id1 = 0 and
+        exists(AstNode node | id2 = idOfTypeParameterAstNode(node) |
           node = tp0.(TypeParamTypeParameter).getTypeParam() or
           node = tp0.(AssociatedTypeTypeParameter).getTypeAlias() or
           node = tp0.(SelfTypeParameter).getTrait() or
           node = tp0.(ImplTraitTypeTypeParameter).getImplTraitTypeRepr()
         )
         or
-        exists(TupleTypeParameter ttp, int maxArity |
-          maxArity = max(int i | i = any(TupleType tt).getArity()) and
-          tp0 = ttp and
-          kind = 3 and
-          id = ttp.getTupleType().getArity() * maxArity + ttp.getIndex()
-        )
+        kind = 4 and
+        id1 = tp0.(TupleTypeParameter).getTupleType().getArity() and
+        id2 = tp0.(TupleTypeParameter).getIndex()
       |
-        tp0 order by kind, id
+        tp0 order by kind, id1, id2
       )
   }
 }

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

@@ -258,6 +258,12 @@ class ImplTraitTypeReprMention extends TypeMention instanceof ImplTraitTypeRepr
   override Type resolveTypeAt(TypePath typePath) {
     typePath.isEmpty() and
     result.(ImplTraitType).getImplTraitTypeRepr() = this
+    or
+    exists(ImplTraitTypeParameter tp |
+      this = tp.getImplTraitTypeRepr() and
+      typePath = TypePath::singleton(tp) and
+      result = TTypeParamTypeParameter(tp.getTypeParam())
+    )
   }
 }
 

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

@@ -1,8 +1,8 @@
 multipleCallTargets
 | dereference.rs:61:15:61:24 | e1.deref() |
-| main.rs:2253:13:2253:31 | ...::from(...) |
-| main.rs:2254:13:2254:31 | ...::from(...) |
-| main.rs:2255:13:2255:31 | ...::from(...) |
-| main.rs:2261:13:2261:31 | ...::from(...) |
-| main.rs:2262:13:2262:31 | ...::from(...) |
-| main.rs:2263:13:2263:31 | ...::from(...) |
+| main.rs:2278:13:2278:31 | ...::from(...) |
+| main.rs:2279:13:2279:31 | ...::from(...) |
+| main.rs:2280:13:2280:31 | ...::from(...) |
+| main.rs:2286:13:2286:31 | ...::from(...) |
+| main.rs:2287:13:2287:31 | ...::from(...) |
+| main.rs:2288:13:2288:31 | ...::from(...) |

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

@@ -1913,8 +1913,10 @@ mod async_ {
 }
 
 mod impl_trait {
+    #[derive(Copy, Clone)]
     struct S1;
     struct S2;
+    struct S3<T3>(T3);
 
     trait Trait1 {
         fn f1(&self) {} // Trait1f1
@@ -1946,6 +1948,13 @@ mod impl_trait {
         }
     }
 
+    impl<T: Clone> MyTrait<T> for S3<T> {
+        fn get_a(&self) -> T {
+            let S3(t) = self;
+            t.clone()
+        }
+    }
+
     fn get_a_my_trait() -> impl MyTrait<S2> {
         S1
     }
@@ -1954,6 +1963,18 @@ mod impl_trait {
         t.get_a() // $ target=MyTrait::get_a
     }
 
+    fn get_a_my_trait2<T: Clone>(x: T) -> impl MyTrait<T> {
+        S3(x)
+    }
+
+    fn get_a_my_trait3<T: Clone>(x: T) -> Option<impl MyTrait<T>> {
+        Some(S3(x))
+    }
+
+    fn get_a_my_trait4<T: Clone>(x: T) -> (impl MyTrait<T>, impl MyTrait<T>) {
+        (S3(x.clone()), S3(x)) // $ target=clone
+    }
+
     fn uses_my_trait2<A>(t: impl MyTrait<A>) -> A {
         t.get_a() // $ target=MyTrait::get_a
     }
@@ -1967,6 +1988,10 @@ mod impl_trait {
         let a = get_a_my_trait(); // $ target=get_a_my_trait
         let c = uses_my_trait2(a); // $ type=c:S2 target=uses_my_trait2
         let d = uses_my_trait2(S1); // $ type=d:S2 target=uses_my_trait2
+        let e = get_a_my_trait2(S1).get_a(); // $ target=get_a_my_trait2 target=MyTrait::get_a type=e:S1
+        // For this function the `impl` type does not appear in the root of the return type
+        let f = get_a_my_trait3(S1).unwrap().get_a(); // $ target=get_a_my_trait3 target=unwrap target=MyTrait::get_a type=f:S1
+        let g = get_a_my_trait4(S1).0.get_a(); // $ target=get_a_my_trait4 target=MyTrait::get_a type=g:S1
     }
 }
 
@@ -2425,7 +2450,7 @@ mod tuples {
 
         let pair = [1, 1].into(); // $ type=pair:(T_2) type=pair:0(2).i32 type=pair:1(2).i32 MISSING: target=into
         match pair {
-            (0,0) => print!("unexpected"),
+            (0, 0) => print!("unexpected"),
             _ => print!("expected"),
         }
         let x = pair.0; // $ type=x:i32