Rust: Avoid mixing up type parameters and associated types in path re…

…solution
github · paldepind · Jul 22, 2025 · Jul 21, 2025 · Jul 21, 2025 · Jul 21, 2025
commit ac6715fb3a08f18cd5650e6496d57e423271e2c7
@@ -112,13 +112,18 @@ abstract class ItemNode extends Locatable {
     result = this.(SourceFileItemNode).getSuper()
   }
 
-
+
+  /**
+   * Gets a child item of this item that has the specified name.
+   *
+   * This predicate is a helper for resolving paths and is used in conjunction
+   * with other successor methods like `getADescendant` and `getImmediateParent`.
+   * It identifies a child item by matching its name and its immediate parent.
+   */
-
+
+  /**
+   * Gets a child item of this item that has the specified name.
+   *
+   * This predicate is a helper for resolving paths and is used in conjunction
+   * with other successor methods like `getADescendant` and `getImmediateParent`.
+   * It identifies a child item by matching its name and its immediate parent.
+   */
+  pragma[nomagic]
+  private ItemNode getAChildSuccessor(string name) {
+    this = result.getImmediateParent() and
+    name = result.getName()
+  }
+
   cached
   ItemNode getASuccessorRec(string name) {
     Stages::PathResolutionStage::ref() and
     sourceFileEdge(this, name, result)
     or
-    this = result.getImmediateParent() and
-    name = result.getName()
+    result = this.getAChildSuccessor(name)
     or
     fileImportEdge(this, name, result)
     or
@@ -224,6 +229,38 @@ abstract class ItemNode extends Locatable {
     result.(CrateItemNode).isPotentialDollarCrateTarget()
   }
 
+  /**
+   * Holds if the successor `item` with the name `name` is not available locally
+   * for unqualified paths.
+   *
+   * This has the effect that a path of the form `name` inside `this` will not
+   * resolve to `item`.
-   * resolve to `item`.
+   * resolve to `item`.
+   *
+   * ## Specific Scenarios
+   * In Rust, associated items (such as methods, associated types, or constants) 
+   * defined within an `impl` or `trait` block are not directly accessible 
+   * without qualification. To access these items, a `Self::` prefix is required.
+   *
+   * For example:
+   * ```
+   * impl MyTrait for MyType {
+   *     fn my_method() {}
+   * }
+   *
+   * // Inside the `impl` block, `my_method` must be accessed as `Self::my_method`.
+   * ```
+   *
+   * This predicate identifies such cases where unqualified access is not allowed.
+   *
+   * ## References
+   * For more details, see the Rust reference on [associated items](https://doc.rust-lang.org/reference/items/associated-items.html).
-   * resolve to `item`.
+   * resolve to `item`.
+   *
+   * ## Specific Scenarios
+   * In Rust, associated items (such as methods, associated types, or constants) 
+   * defined within an `impl` or `trait` block are not directly accessible 
+   * without qualification. To access these items, a `Self::` prefix is required.
+   *
+   * For example:
+   * ```
+   * impl MyTrait for MyType {
+   *     fn my_method() {}
+   * }
+   *
+   * // Inside the `impl` block, `my_method` must be accessed as `Self::my_method`.
+   * ```
+   *
+   * This predicate identifies such cases where unqualified access is not allowed.
+   *
+   * ## References
+   * For more details, see the Rust reference on [associated items](https://doc.rust-lang.org/reference/items/associated-items.html).
+   */
+  pragma[nomagic]
+  predicate excludedLocally(string name, ItemNode item) {
+    // Associated items in an impl or trait block are not directly available
+    // inside the block, they require a qualified path with a `Self` prefix.
+    item = this.getAChildSuccessor(name) and
+    this instanceof ImplOrTraitItemNode and
+    item instanceof AssocItemNode
+  }
+
+  /**
+   * Holds if the successor `item` with the name `name` is not available
+   * externally for qualified paths that resolve to this item.
+   *
+   * This has the effect that a path of the form `Qualifier::name`, where
+   * `Qualifier` resolves to this item, will not resolve to `item`.
-   * `Qualifier` resolves to this item, will not resolve to `item`.
+   * `Qualifier` resolves to this item, will not resolve to `item`.
+   *
+   * ## Examples
+   *
+   * Consider the following Rust code:
+   *
+   * ```
+   * impl<T> MyStruct<T> {
+   *     fn new() -> Self {
+   *         // ...
+   *     }
+   * }
+   * ```
+   *
+   * Here, the type parameter `T` is not accessible outside the `impl` block.
+   * For example, the following code would result in a compilation error:
+   *
+   * ```
+   * let x: MyStruct::T; // Error: `T` is not accessible here
+   * ```
+   *
+   * The `excludedExternally` predicate ensures that such type parameters are
+   * excluded from external path resolution.
-   * `Qualifier` resolves to this item, will not resolve to `item`.
+   * `Qualifier` resolves to this item, will not resolve to `item`.
+   *
+   * ## Examples
+   *
+   * Consider the following Rust code:
+   *
+   * ```
+   * impl<T> MyStruct<T> {
+   *     fn new() -> Self {
+   *         // ...
+   *     }
+   * }
+   * ```
+   *
+   * Here, the type parameter `T` is not accessible outside the `impl` block.
+   * For example, the following code would result in a compilation error:
+   *
+   * ```
+   * let x: MyStruct::T; // Error: `T` is not accessible here
+   * ```
+   *
+   * The `excludedExternally` predicate ensures that such type parameters are
+   * excluded from external path resolution.
+   */
+  pragma[nomagic]
+  predicate excludedExternally(string name, ItemNode item) {
+    // Type parameters for an `impl` or trait block are not available outside of
+    // the block.
+    item = this.getAChildSuccessor(name) and
+    this instanceof ImplOrTraitItemNode and
+    item instanceof TypeParamItemNode
+  }
+
   pragma[nomagic]
   private predicate hasSourceFunction(string name) {
     this.getASuccessorFull(name).(Function).fromSource()
@@ -1145,7 +1182,9 @@ pragma[nomagic]
 private predicate declares(ItemNode item, Namespace ns, string name) {
   exists(ItemNode child | child.getImmediateParent() = item |
     child.getName() = name and
-    child.getNamespace() = ns
+    child.getNamespace() = ns and
+    // If `item` is excluded locally then it does not declare `name`.
+    not item.excludedLocally(name, child)
     or
     useTreeDeclares(child.(Use).getUseTree(), name) and
     exists(ns) // `use foo::bar` can refer to both a value and a type
@@ -1193,38 +1232,27 @@ private ItemNode getOuterScope(ItemNode i) {
   result = i.getImmediateParent()
 }
 
-pragma[nomagic]
-private ItemNode getAdjustedEnclosing(ItemNode encl0, Namespace ns) {
-  // functions in `impl` blocks need to use explicit `Self::` to access other
-  // functions in the `impl` block
-  if encl0 instanceof ImplOrTraitItemNode and ns.isValue()
-  then result = encl0.getImmediateParent()
-  else result = encl0
-}
-
 /**
  * Holds if the unqualified path `p` references an item named `name`, and `name`
  * may be looked up in the `ns` namespace inside enclosing item `encl`.
  */
 pragma[nomagic]
 private predicate unqualifiedPathLookup(ItemNode encl, string name, Namespace ns, RelevantPath p) {
-  exists(ItemNode encl0 | encl = getAdjustedEnclosing(encl0, ns) |
-    // lookup in the immediately enclosing item
-    p.isUnqualified(name) and
-    encl0.getADescendant() = p and
-    exists(ns) and
-    not name = ["crate", "$crate", "super", "self"]
-    or
-    // lookup in an outer scope, but only if the item is not declared in inner scope
-    exists(ItemNode mid |
-      unqualifiedPathLookup(mid, name, ns, p) and
-      not declares(mid, ns, name) and
-      not (
-        name = "Self" and
-        mid = any(ImplOrTraitItemNode i).getAnItemInSelfScope()
-      ) and
-      encl0 = getOuterScope(mid)
-    )
+  // lookup in the immediately enclosing item
+  p.isUnqualified(name) and
+  encl.getADescendant() = p and
+  exists(ns) and
+  not name = ["crate", "$crate", "super", "self"]
+  or
+  // lookup in an outer scope, but only if the item is not declared in inner scope
+  exists(ItemNode mid |
+    unqualifiedPathLookup(mid, name, ns, p) and
+    not declares(mid, ns, name) and
+    not (
+      name = "Self" and
+      mid = any(ImplOrTraitItemNode i).getAnItemInSelfScope()
+    ) and
+    encl = getOuterScope(mid)
   )
 }
 
@@ -1245,10 +1273,10 @@ private predicate sourceFileHasCratePathTc(ItemNode i1, ItemNode i2) =
 
 /**
  * Holds if the unqualified path `p` references a keyword item named `name`, and
- * `name` may be looked up in the `ns` namespace inside enclosing item `encl`.
+ * `name` may be looked up inside enclosing item `encl`.
  */
 pragma[nomagic]
-private predicate keywordLookup(ItemNode encl, string name, Namespace ns, RelevantPath p) {
+private predicate keywordLookup(ItemNode encl, string name, RelevantPath p) {
   // For `($)crate`, jump directly to the root module
   exists(ItemNode i | p.isCratePath(name, i) |
     encl instanceof SourceFile and
@@ -1259,18 +1287,17 @@ private predicate keywordLookup(ItemNode encl, string name, Namespace ns, Releva
   or
   name = ["super", "self"] and
   p.isUnqualified(name) and
-  exists(ItemNode encl0 |
-    encl0.getADescendant() = p and
-    encl = getAdjustedEnclosing(encl0, ns)
-  )
+  encl.getADescendant() = p
 }
 
 pragma[nomagic]
 private ItemNode unqualifiedPathLookup(RelevantPath p, Namespace ns) {
-  exists(ItemNode encl, string name | result = getASuccessorFull(encl, name, ns) |
+  exists(ItemNode encl, string name |
+    result = getASuccessorFull(encl, name, ns) and not encl.excludedLocally(name, result)
+  |
     unqualifiedPathLookup(encl, name, ns, p)
     or
-    keywordLookup(encl, name, ns, p)
+    keywordLookup(encl, name, p) and exists(ns)
   )
 }
 
@@ -1291,7 +1318,8 @@ private ItemNode resolvePath0(RelevantPath path, Namespace ns) {
   or
   exists(ItemNode q, string name |
     q = resolvePathQualifier(path, name) and
-    result = getASuccessorFull(q, name, ns)
+    result = getASuccessorFull(q, name, ns) and
+    not q.excludedExternally(name, result)
   )
   or
   result = resolveUseTreeListItem(_, _, path) and

@@ -661,29 +661,29 @@ mod associated_types {
             Error, // IError
         > Reduce // $ item=IReduce
         for MyImpl<
-            Input, // $ item=IInput SPURIOUS: item=IInputAssociated
-            Error, // $ item=IError SPURIOUS: item=IErrorAssociated
+            Input, // $ item=IInput
+            Error, // $ item=IError
         > // $ item=MyImpl
     {
         type Input = Result<
-            Input,       // $ item=IInput SPURIOUS: item=IInputAssociated
-            Self::Error, // $ item=IErrorAssociated SPURIOUS: item=IError
+            Input,       // $ item=IInput
+            Self::Error, // $ item=IErrorAssociated
         > // $ item=Result
         ; // IInputAssociated
         type Error = Option<
-          Error // $ item=IError SPURIOUS: item=IErrorAssociated
+          Error // $ item=IError
         > // $ item=Option
         ; // IErrorAssociated
         type Output =
-            Input // $ item=IInput SPURIOUS: item=IInputAssociated
+            Input // $ item=IInput
         ; // IOutputAssociated
 
         fn feed(
             &mut self,
-            item: Self::Input // $ item=IInputAssociated SPURIOUS: item=IInput
+            item: Self::Input // $ item=IInputAssociated
         ) -> Result<
             Self::Output, // $ item=IOutputAssociated
-            Self::Error // $ item=IErrorAssociated SPURIOUS: item=IError
+            Self::Error // $ item=IErrorAssociated
         > { // $ item=Result
             item
         }

@@ -297,28 +297,20 @@ resolvePath
 | main.rs:662:11:662:16 | Reduce | main.rs:643:5:651:5 | trait Reduce |
 | main.rs:663:13:666:9 | MyImpl::<...> | main.rs:653:5:656:5 | struct MyImpl |
 | main.rs:664:13:664:17 | Input | main.rs:660:13:660:17 | Input |
-| main.rs:664:13:664:17 | Input | main.rs:668:9:672:9 | type Input |
 | main.rs:665:13:665:17 | Error | main.rs:661:13:661:17 | Error |
-| main.rs:665:13:665:17 | Error | main.rs:672:11:676:9 | type Error |
 | main.rs:668:22:671:9 | Result::<...> | {EXTERNAL LOCATION} | enum Result |
 | main.rs:669:13:669:17 | Input | main.rs:660:13:660:17 | Input |
-| main.rs:669:13:669:17 | Input | main.rs:668:9:672:9 | type Input |
 | main.rs:670:13:670:16 | Self | main.rs:658:5:690:5 | impl Reduce for MyImpl::<...> { ... } |
-| main.rs:670:13:670:23 | ...::Error | main.rs:661:13:661:17 | Error |
 | main.rs:670:13:670:23 | ...::Error | main.rs:672:11:676:9 | type Error |
 | main.rs:673:22:675:9 | Option::<...> | {EXTERNAL LOCATION} | enum Option |
 | main.rs:674:11:674:15 | Error | main.rs:661:13:661:17 | Error |
-| main.rs:674:11:674:15 | Error | main.rs:672:11:676:9 | type Error |
 | main.rs:678:13:678:17 | Input | main.rs:660:13:660:17 | Input |
-| main.rs:678:13:678:17 | Input | main.rs:668:9:672:9 | type Input |
 | main.rs:683:19:683:22 | Self | main.rs:658:5:690:5 | impl Reduce for MyImpl::<...> { ... } |
-| main.rs:683:19:683:29 | ...::Input | main.rs:660:13:660:17 | Input |
 | main.rs:683:19:683:29 | ...::Input | main.rs:668:9:672:9 | type Input |
 | main.rs:684:14:687:9 | Result::<...> | {EXTERNAL LOCATION} | enum Result |
 | main.rs:685:13:685:16 | Self | main.rs:658:5:690:5 | impl Reduce for MyImpl::<...> { ... } |
 | main.rs:685:13:685:24 | ...::Output | main.rs:676:11:679:9 | type Output |
 | main.rs:686:13:686:16 | Self | main.rs:658:5:690:5 | impl Reduce for MyImpl::<...> { ... } |
-| main.rs:686:13:686:23 | ...::Error | main.rs:661:13:661:17 | Error |
 | main.rs:686:13:686:23 | ...::Error | main.rs:672:11:676:9 | type Error |
 | main.rs:693:5:693:7 | std | {EXTERNAL LOCATION} | Crate(std@0.0.0) |
 | main.rs:693:11:693:14 | self | {EXTERNAL LOCATION} | Crate(std@0.0.0) |

@@ -2162,7 +2162,7 @@ mod loops {
 
         for i in [1, 2, 3] {} // $ type=i:i32
         for i in [1, 2, 3].map(|x| x + 1) {} // $ target=map MISSING: type=i:i32
-        for i in [1, 2, 3].into_iter() {} // $ target=into_iter MISSING: type=i:i32
+        for i in [1, 2, 3].into_iter() {} // $ target=into_iter type=i:i32
 
         let vals1 = [1u8, 2, 3]; // $ type=vals1:[T;...].u8
         for u in vals1 {} // $ type=u:u8

@@ -3526,8 +3526,12 @@ inferType
 | main.rs:2164:22:2164:22 | 2 |  | {EXTERNAL LOCATION} | i32 |
 | main.rs:2164:25:2164:25 | 3 |  | {EXTERNAL LOCATION} | i32 |
 | main.rs:2164:40:2164:40 | 1 |  | {EXTERNAL LOCATION} | i32 |
+| main.rs:2165:13:2165:13 | i |  | {EXTERNAL LOCATION} | Item |
+| main.rs:2165:13:2165:13 | i |  | {EXTERNAL LOCATION} | i32 |
 | main.rs:2165:18:2165:26 | [...] |  | file://:0:0:0:0 | [] |
 | main.rs:2165:18:2165:26 | [...] | [T;...] | {EXTERNAL LOCATION} | i32 |
+| main.rs:2165:18:2165:38 | ... .into_iter() |  | {EXTERNAL LOCATION} | IntoIter |
+| main.rs:2165:18:2165:38 | ... .into_iter() | T | {EXTERNAL LOCATION} | i32 |
 | main.rs:2165:19:2165:19 | 1 |  | {EXTERNAL LOCATION} | i32 |
 | main.rs:2165:22:2165:22 | 2 |  | {EXTERNAL LOCATION} | i32 |
 | main.rs:2165:25:2165:25 | 3 |  | {EXTERNAL LOCATION} | i32 |
@@ -3739,11 +3743,8 @@ inferType
 | main.rs:2226:39:2226:39 | 2 |  | {EXTERNAL LOCATION} | u16 |
 | main.rs:2226:42:2226:42 | 3 |  | {EXTERNAL LOCATION} | i32 |
 | main.rs:2226:42:2226:42 | 3 |  | {EXTERNAL LOCATION} | u16 |
-| main.rs:2227:13:2227:13 | u |  | {EXTERNAL LOCATION} | Vec |
 | main.rs:2227:13:2227:13 | u |  | {EXTERNAL LOCATION} | u16 |
 | main.rs:2227:13:2227:13 | u |  | file://:0:0:0:0 | & |
-| main.rs:2227:13:2227:13 | u | A | {EXTERNAL LOCATION} | Global |
-| main.rs:2227:13:2227:13 | u | T | {EXTERNAL LOCATION} | u16 |
 | main.rs:2227:18:2227:23 | vals4a |  | {EXTERNAL LOCATION} | Vec |
 | main.rs:2227:18:2227:23 | vals4a | A | {EXTERNAL LOCATION} | Global |
 | main.rs:2227:18:2227:23 | vals4a | T | {EXTERNAL LOCATION} | u16 |
@@ -3773,13 +3774,9 @@ inferType
 | main.rs:2232:38:2232:38 | 2 |  | {EXTERNAL LOCATION} | u32 |
 | main.rs:2232:41:2232:41 | 3 |  | {EXTERNAL LOCATION} | i32 |
 | main.rs:2232:41:2232:41 | 3 |  | {EXTERNAL LOCATION} | u32 |
-| main.rs:2233:13:2233:13 | u |  | {EXTERNAL LOCATION} | Vec |
 | main.rs:2233:13:2233:13 | u |  | {EXTERNAL LOCATION} | i32 |
 | main.rs:2233:13:2233:13 | u |  | {EXTERNAL LOCATION} | u32 |
 | main.rs:2233:13:2233:13 | u |  | file://:0:0:0:0 | & |
-| main.rs:2233:13:2233:13 | u | A | {EXTERNAL LOCATION} | Global |
-| main.rs:2233:13:2233:13 | u | T | {EXTERNAL LOCATION} | i32 |
-| main.rs:2233:13:2233:13 | u | T | {EXTERNAL LOCATION} | u32 |
 | main.rs:2233:18:2233:22 | vals5 |  | {EXTERNAL LOCATION} | Vec |
 | main.rs:2233:18:2233:22 | vals5 | A | {EXTERNAL LOCATION} | Global |
 | main.rs:2233:18:2233:22 | vals5 | T | {EXTERNAL LOCATION} | i32 |
@@ -3801,12 +3798,8 @@ inferType
 | main.rs:2235:39:2235:39 | 2 |  | {EXTERNAL LOCATION} | u64 |
 | main.rs:2235:42:2235:42 | 3 |  | {EXTERNAL LOCATION} | i32 |
 | main.rs:2235:42:2235:42 | 3 |  | {EXTERNAL LOCATION} | u64 |
-| main.rs:2236:13:2236:13 | u |  | {EXTERNAL LOCATION} | Vec |
 | main.rs:2236:13:2236:13 | u |  | file://:0:0:0:0 | & |
 | main.rs:2236:13:2236:13 | u | &T | {EXTERNAL LOCATION} | u64 |
-| main.rs:2236:13:2236:13 | u | A | {EXTERNAL LOCATION} | Global |
-| main.rs:2236:13:2236:13 | u | T | file://:0:0:0:0 | & |
-| main.rs:2236:13:2236:13 | u | T.&T | {EXTERNAL LOCATION} | u64 |
 | main.rs:2236:18:2236:22 | vals6 |  | {EXTERNAL LOCATION} | Vec |
 | main.rs:2236:18:2236:22 | vals6 | A | {EXTERNAL LOCATION} | Global |
 | main.rs:2236:18:2236:22 | vals6 | T | file://:0:0:0:0 | & |
@@ -3821,11 +3814,8 @@ inferType
 | main.rs:2239:9:2239:13 | vals7 | A | {EXTERNAL LOCATION} | Global |
 | main.rs:2239:9:2239:13 | vals7 | T | {EXTERNAL LOCATION} | u8 |
 | main.rs:2239:20:2239:22 | 1u8 |  | {EXTERNAL LOCATION} | u8 |
-| main.rs:2240:13:2240:13 | u |  | {EXTERNAL LOCATION} | Vec |
 | main.rs:2240:13:2240:13 | u |  | {EXTERNAL LOCATION} | u8 |
 | main.rs:2240:13:2240:13 | u |  | file://:0:0:0:0 | & |
-| main.rs:2240:13:2240:13 | u | A | {EXTERNAL LOCATION} | Global |
-| main.rs:2240:13:2240:13 | u | T | {EXTERNAL LOCATION} | u8 |
 | main.rs:2240:18:2240:22 | vals7 |  | {EXTERNAL LOCATION} | Vec |
 | main.rs:2240:18:2240:22 | vals7 | A | {EXTERNAL LOCATION} | Global |
 | main.rs:2240:18:2240:22 | vals7 | T | {EXTERNAL LOCATION} | u8 |