Rust: Special-case Self::AssocType in path resolution

Author: hvitved

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

@@ -1897,6 +1897,16 @@ private ItemNode resolvePathCandQualified(PathExt qualifier, ItemNode q, PathExt
     q = resolvePathCandQualifier(qualifier, path, name) and
     result = getASuccessor(q, name, ns, kind, useOpt) and
     checkQualifiedVisibility(path, result, kind, useOpt)
+  |
+    // Special case for `Self::AssocType`; this always refers to the associated
+    // type in the enclosing `impl` block, if available.
+    forall(ImplItemNode impl, TypeAliasItemNode alias |
+      qualifier = impl.getASelfPath() and alias = result
+    |
+      alias = impl.getAnAssocItem()
+      or
+      not exists(impl.getAssocItem(name).(TypeAliasItemNode))
+    )
   )
 }
 

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

@@ -4,6 +4,3 @@ multipleCallTargets
 | main.rs:369:9:371:16 | ...::f(...) |
 | main.rs:450:9:454:16 | ...::f(...) |
 | main.rs:455:9:459:16 | ...::f(...) |
-multiplePathResolutions
-| main.rs:492:20:492:34 | ...::AssocType |
-| main.rs:504:20:504:34 | ...::AssocType |

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

@@ -489,7 +489,7 @@ mod m16 {
         ; // S2Trait3AssocType
 
         fn f(&self) {
-            let x: Self::AssocType = 42; // $ item=S2Trait3AssocType $ SPURIOUS: item=S2Trait4AssocType
+            let x: Self::AssocType = 42; // $ item=S2Trait3AssocType
         } // S2asTrait3::f
     }
 
@@ -501,7 +501,7 @@ mod m16 {
         fn g(&self) {
             Self::f(&self); // $ item=S2asTrait3::f
             S2::f(&self); // $ item=S2asTrait3::f
-            let x: Self::AssocType = true; // $ item=S2Trait4AssocType $ SPURIOUS: item=S2Trait3AssocType
+            let x: Self::AssocType = true; // $ item=S2Trait4AssocType
         }
     }
 }

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

@@ -269,7 +269,6 @@ resolvePath
 | main.rs:488:26:488:28 | i32 | {EXTERNAL LOCATION} | struct i32 |
 | main.rs:492:20:492:23 | Self | main.rs:484:5:484:14 | struct S2 |
 | main.rs:492:20:492:34 | ...::AssocType | main.rs:487:26:489:9 | type AssocType |
-| main.rs:492:20:492:34 | ...::AssocType | main.rs:497:26:499:9 | type AssocType |
 | main.rs:497:10:497:15 | Trait4 | main.rs:478:5:482:5 | trait Trait4 |
 | main.rs:497:21:497:22 | S2 | main.rs:484:5:484:14 | struct S2 |
 | main.rs:498:26:498:29 | bool | {EXTERNAL LOCATION} | struct bool |
@@ -278,7 +277,6 @@ resolvePath
 | main.rs:503:13:503:14 | S2 | main.rs:484:5:484:14 | struct S2 |
 | main.rs:503:13:503:17 | ...::f | main.rs:489:11:493:9 | fn f |
 | main.rs:504:20:504:23 | Self | main.rs:484:5:484:14 | struct S2 |
-| main.rs:504:20:504:34 | ...::AssocType | main.rs:487:26:489:9 | type AssocType |
 | main.rs:504:20:504:34 | ...::AssocType | main.rs:497:26:499:9 | type AssocType |
 | main.rs:521:14:521:16 | Foo | main.rs:511:9:513:9 | trait Foo |
 | main.rs:521:22:521:22 | X | main.rs:519:9:519:21 | struct X |

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

@@ -11,7 +11,3 @@ multipleCallTargets
 | main.rs:2642:13:2642:31 | ...::from(...) |
 | main.rs:2643:13:2643:31 | ...::from(...) |
 | main.rs:2644:13:2644:31 | ...::from(...) |
-multiplePathResolutions
-| main.rs:2463:41:2463:52 | ...::Output |
-| main.rs:2472:38:2472:49 | ...::Output |
-| main.rs:2484:42:2484:53 | ...::Output |