Rust: Make impl blocks only give rise to direct trait implementation

Author: paldepind

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

@@ -179,48 +179,52 @@ private module Input2 implements InputSig2 {
    * inference module for more information.
    */
   predicate conditionSatisfiesConstraint(
-    TypeAbstraction abs, TypeMention condition, TypeMention constraint
+    TypeAbstraction abs, TypeMention condition, TypeMention constraint, boolean transitive
   ) {
     // `impl` blocks implementing traits
+    transitive = false and
     exists(Impl impl |
       abs = impl and
       condition = impl.getSelfTy() and
       constraint = impl.getTrait()
     )
     or
-    // supertraits
-    exists(Trait trait |
-      abs = trait and
-      condition = trait and
-      constraint = trait.getATypeBound().getTypeRepr()
-    )
-    or
-    // trait bounds on type parameters
-    exists(TypeParam param |
-      abs = param.getATypeBound() and
-      condition = param and
-      constraint = abs.(TypeBound).getTypeRepr()
-    )
-    or
-    // the implicit `Self` type parameter satisfies the trait
-    exists(SelfTypeParameterMention self |
-      abs = self and
-      condition = self and
-      constraint = self.getTrait()
-    )
-    or
-    exists(ImplTraitTypeRepr impl |
-      abs = impl and
-      condition = impl and
-      constraint = impl.getTypeBoundList().getABound().getTypeRepr()
-    )
-    or
-    // a `dyn Trait` type implements `Trait`. See the comment on
-    // `DynTypeBoundListMention` for further details.
-    exists(DynTraitTypeRepr object |
-      abs = object and
-      condition = object.getTypeBoundList() and
-      constraint = object.getTrait()
+    transitive = true and
+    (
+      // supertraits
+      exists(Trait trait |
+        abs = trait and
+        condition = trait and
+        constraint = trait.getATypeBound().getTypeRepr()
+      )
+      or
+      // trait bounds on type parameters
+      exists(TypeParam param |
+        abs = param.getATypeBound() and
+        condition = param and
+        constraint = abs.(TypeBound).getTypeRepr()
+      )
+      or
+      // the implicit `Self` type parameter satisfies the trait
+      exists(SelfTypeParameterMention self |
+        abs = self and
+        condition = self and
+        constraint = self.getTrait()
+      )
+      or
+      exists(ImplTraitTypeRepr impl |
+        abs = impl and
+        condition = impl and
+        constraint = impl.getTypeBoundList().getABound().getTypeRepr()
+      )
+      or
+      // a `dyn Trait` type implements `Trait`. See the comment on
+      // `DynTypeBoundListMention` for further details.
+      exists(DynTraitTypeRepr object |
+        abs = object and
+        condition = object.getTypeBoundList() and
+        constraint = object.getTrait()
+      )
     )
   }
 }
@@ -3616,10 +3620,10 @@ private module Debug {
   }
 
   predicate debugConditionSatisfiesConstraint(
-    TypeAbstraction abs, TypeMention condition, TypeMention constraint
+    TypeAbstraction abs, TypeMention condition, TypeMention constraint, boolean transitive
   ) {
     abs = getRelevantLocatable() and
-    Input2::conditionSatisfiesConstraint(abs, condition, constraint)
+    Input2::conditionSatisfiesConstraint(abs, condition, constraint, transitive)
   }
 
   predicate debugInferShorthandSelfType(ShorthandSelfParameterMention self, TypePath path, Type t) {

rust/ql/lib/codeql/rust/internal/typeinference/FunctionType.qll

@@ -72,16 +72,24 @@ module FunctionPositionMatchingInput {
 }
 
 private newtype TAssocFunctionType =
-  /** An associated function `f` that should be specialized for `i` at `pos`. */
-  MkAssocFunctionType(Function f, ImplOrTraitItemNode i, FunctionPosition pos) {
-    f = i.getASuccessor(_) and exists(pos.getTypeMention(f))
+  /** An associated function `f` in `parent` should be specialized for `i` at `pos`. */
+  MkAssocFunctionType(
+    ImplOrTraitItemNode parent, Function f, ImplOrTraitItemNode i, FunctionPosition pos
+  ) {
+    parent.getAnAssocItem() = f and
+    i.getASuccessor(_) = f and
+    // When `f` is not directly in `i`, the `parent` should be satisfiable
+    // through `i`. This ensures that `parent` is either a supertrait of `i` or
+    // `i` in an `impl` block implementing `parent`.
+    (parent = i or BaseTypes::rootTypesSatisfaction(_, TTrait(parent), i, _, _)) and
+    exists(pos.getTypeMention(f))
   }
 
-bindingset[condition, constraint, tp]
+bindingset[abs, constraint, tp]
 private Type getTraitConstraintTypeAt(
-  TypeMention condition, TypeMention constraint, TypeParameter tp, TypePath path
+  TypeAbstraction abs, TypeMention constraint, TypeParameter tp, TypePath path
 ) {
-  BaseTypes::conditionSatisfiesConstraintTypeAt(_, condition, constraint,
+  BaseTypes::conditionSatisfiesConstraintTypeAt(abs, _, constraint,
     TypePath::singleton(tp).appendInverse(path), result)
 }
 
@@ -91,28 +99,19 @@ private Type getTraitConstraintTypeAt(
  */
 pragma[nomagic]
 Type getAssocFunctionTypeAt(Function f, ImplOrTraitItemNode i, FunctionPosition pos, TypePath path) {
-  exists(MkAssocFunctionType(f, i, pos)) and
-  (
+  exists(ImplOrTraitItemNode parent | exists(MkAssocFunctionType(parent, f, i, pos)) |
     // No specialization needed when the function is directly in the trait or
     // impl block or the declared type is not a type parameter
-    (i.getAnAssocItem() = f or not result instanceof TypeParameter) and
+    (parent = i or not result instanceof TypeParameter) and
     result = pos.getTypeMention(f).resolveTypeAt(path)
     or
-    not i.getAnAssocItem() = f and
-    exists(TypePath prefix, TypePath suffix, TypeParameter tp |
+    exists(TypePath prefix, TypePath suffix, TypeParameter tp, TypeMention constraint |
+      BaseTypes::rootTypesSatisfaction(_, TTrait(parent), i, _, constraint) and
       path = prefix.append(suffix) and
-      tp = pos.getTypeMention(f).resolveTypeAt(prefix)
-    |
+      tp = pos.getTypeMention(f).resolveTypeAt(prefix) and
       if tp = TSelfTypeParameter(_)
       then result = resolveImplOrTraitType(i, suffix)
-      else
-        exists(TraitItemNode trait, TypeMention condition, TypeMention constraint |
-          trait.getAnAssocItem() = f and
-          BaseTypes::rootTypesSatisfaction(_, TTrait(trait), _, condition, constraint) and
-          result = getTraitConstraintTypeAt(condition, constraint, tp, suffix)
-        |
-          condition = i.(Trait) or condition = i.(Impl).getSelfTy()
-        )
+      else result = getTraitConstraintTypeAt(i, constraint, tp, suffix)
     )
   )
 }
@@ -134,31 +133,33 @@ Type getAssocFunctionTypeAt(Function f, ImplOrTraitItemNode i, FunctionPosition
  *   fn m3(self);              // self3
  * }
  *
- * impl T2 for X {
+ * impl T1 for X {
  *   fn m1(self) { ... }       // self4
+ * }
  *
+ * impl T2 for X {
  *   fn m3(self) { ... }       // self5
  * }
  * ```
  *
- * param   | `impl` or trait | type
- * ------- | --------------- | ----
- * `self1` | `trait T1`      | `T1`
- * `self1` | `trait T2`      | `T2`
- * `self2` | `trait T1`      | `T1`
- * `self2` | `trait T2`      | `T2`
- * `self2` | `impl T2 for X` | `X`
- * `self3` | `trait T2`      | `T2`
- * `self4` | `impl T2 for X` | `X`
- * `self5` | `impl T2 for X` | `X`
+ * f    | `impl` or trait | pos    | type
+ * ---- | --------------- | ------ | ----
+ * `m1` | `trait T1`      | `self` | `T1`
+ * `m1` | `trait T2`      | `self` | `T2`
+ * `m2` | `trait T1`      | `self` | `T1`
+ * `m2` | `trait T2`      | `self` | `T2`
+ * `m2` | `impl T1 for X` | `self` | `X`
+ * `m3` | `trait T2`      | `self` | `T2`
+ * `m4` | `impl T2 for X` | `self` | `X`
+ * `m5` | `impl T2 for X` | `self` | `X`
  */
 class AssocFunctionType extends MkAssocFunctionType {
   /**
    * Holds if this function type applies to the function `f` at position `pos`,
    * when viewed as a member of the `impl` or trait item `i`.
    */
   predicate appliesTo(Function f, ImplOrTraitItemNode i, FunctionPosition pos) {
-    this = MkAssocFunctionType(f, i, pos)
+    this = MkAssocFunctionType(_, f, i, pos)
   }
 
   /**

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

@@ -586,10 +586,10 @@ mod impl_overlap {
         println!("{:?}", w.m(x)); // $ target=S3<T>::m
         println!("{:?}", S3::m(&w, x)); // $ target=S3<T>::m
 
-        S4.m(); // $ target=<S4_as_MyTrait1>::m $ SPURIOUS: target=MyTrait1::m
+        S4.m(); // $ target=<S4_as_MyTrait1>::m
         S4::m(&S4); // $ target=<S4_as_MyTrait1>::m $ SPURIOUS: target=MyTrait1::m
-        S5(0i32).m(); // $ target=<S5<i32>_as_MyTrait1>::m $ SPURIOUS: target=MyTrait1::m
-        S5::m(&S5(0i32)); // $ target=<S5<i32>_as_MyTrait1>::m $ SPURIOUS: target=MyTrait1::m
+        S5(0i32).m(); // $ target=<S5<i32>_as_MyTrait1>::m
+        S5::m(&S5(0i32)); // $ target=<S5<i32>_as_MyTrait1>::m
         S5(true).m(); // $ target=MyTrait1::m
         S5::m(&S5(true)); // $ target=MyTrait1::m
     }

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

@@ -5443,7 +5443,6 @@ inferType
 | main.rs:2595:42:2595:42 | 3 |  | {EXTERNAL LOCATION} | i32 |
 | main.rs:2596:9:2596:26 | for ... in ... { ... } |  | file://:0:0:0:0 | () |
 | main.rs:2596:13:2596:13 | u |  | {EXTERNAL LOCATION} | u16 |
-| main.rs:2596:13:2596:13 | u |  | file://:0:0:0:0 | & |
 | main.rs:2596:18:2596:23 | vals4a |  | {EXTERNAL LOCATION} | Vec |
 | main.rs:2596:18:2596:23 | vals4a | A | {EXTERNAL LOCATION} | Global |
 | main.rs:2596:18:2596:23 | vals4a | T | {EXTERNAL LOCATION} | u16 |
@@ -5473,7 +5472,6 @@ inferType
 | main.rs:2602:9:2602:25 | for ... in ... { ... } |  | file://:0:0:0:0 | () |
 | main.rs:2602:13:2602:13 | u |  | {EXTERNAL LOCATION} | i32 |
 | main.rs:2602:13:2602:13 | u |  | {EXTERNAL LOCATION} | u32 |
-| main.rs:2602:13:2602:13 | u |  | file://:0:0:0:0 | & |
 | main.rs:2602:18:2602:22 | vals5 |  | {EXTERNAL LOCATION} | Vec |
 | main.rs:2602:18:2602:22 | vals5 | A | {EXTERNAL LOCATION} | Global |
 | main.rs:2602:18:2602:22 | vals5 | T | {EXTERNAL LOCATION} | i32 |
@@ -5514,7 +5512,6 @@ inferType
 | main.rs:2608:20:2608:22 | 1u8 |  | {EXTERNAL LOCATION} | u8 |
 | main.rs:2609:9:2609:25 | for ... in ... { ... } |  | file://:0:0:0:0 | () |
 | main.rs:2609:13:2609:13 | u |  | {EXTERNAL LOCATION} | u8 |
-| main.rs:2609:13:2609:13 | u |  | file://:0:0:0:0 | & |
 | main.rs:2609:18:2609:22 | vals7 |  | {EXTERNAL LOCATION} | Vec |
 | main.rs:2609:18:2609:22 | vals7 | A | {EXTERNAL LOCATION} | Global |
 | main.rs:2609:18:2609:22 | vals7 | T | {EXTERNAL LOCATION} | u8 |

shared/typeinference/codeql/typeinference/internal/TypeInference.qll

@@ -450,6 +450,8 @@ module Make1<LocationSig Location, InputSig1<Location> Input1> {
      *   free in `condition` and `constraint`,
      * - and for every instantiation of the type parameters from `abs` the
      *   resulting `condition` satisifies the constraint given by `constraint`.
+     * - `transitive` corresponds to wether any further constraints satisifed
+     *   through `constraint` also applies to `condition`.
      *
      * Example in C#:
      * ```csharp
@@ -487,7 +489,7 @@ module Make1<LocationSig Location, InputSig1<Location> Input1> {
      * should be empty.
      */
     predicate conditionSatisfiesConstraint(
-      TypeAbstraction abs, TypeMention condition, TypeMention constraint
+      TypeAbstraction abs, TypeMention condition, TypeMention constraint, boolean transitive
     );
   }
 
@@ -754,13 +756,13 @@ module Make1<LocationSig Location, InputSig1<Location> Input1> {
         private predicate typeCondition(
           Type type, TypeAbstraction abs, TypeMentionTypeTree condition
         ) {
-          conditionSatisfiesConstraint(abs, condition, _) and
+          conditionSatisfiesConstraint(abs, condition, _, _) and
           type = resolveTypeMentionRoot(condition)
         }
 
         pragma[nomagic]
         private predicate typeConstraint(Type type, TypeMentionTypeTree constraint) {
-          conditionSatisfiesConstraint(_, _, constraint) and
+          conditionSatisfiesConstraint(_, _, constraint, _) and
           type = resolveTypeMentionRoot(constraint)
         }
 
@@ -781,12 +783,12 @@ module Make1<LocationSig Location, InputSig1<Location> Input1> {
         TypeAbstraction abs, TypeMention condition, TypeMention constraint, TypePath path, Type t
       ) {
         // base case
-        conditionSatisfiesConstraint(abs, condition, constraint) and
+        conditionSatisfiesConstraint(abs, condition, constraint, _) and
         constraint.resolveTypeAt(path) = t
         or
         // recursive case
         exists(TypeAbstraction midAbs, TypeMention midConstraint, TypeMention midCondition |
-          conditionSatisfiesConstraint(abs, condition, midConstraint) and
+          conditionSatisfiesConstraint(abs, condition, midConstraint, true) and
           // NOTE: `midAbs` describe the free type variables in `midCondition`, hence
           // we use that for instantiation check.
           IsInstantiationOf<TypeMentionTypeTree, TypeMentionTypeTree, IsInstantiationOfInput>::isInstantiationOf(midConstraint,