Unified: Resolve Self in static name binding

Author: hvitved

unified/ql/lib/codeql/unified/internal/NameBindingPlugin.qll

@@ -42,6 +42,12 @@ class NameBindingPlugin extends Unit {
 
   /** Gets the name of the implicit receiver parameter in `callable`, if it has one. */
   string getImplicitReceiverParameterName(Callable callable) { none() }
+
+  /**
+   * Gets the name through which static members of the enclosing class can be
+   * accessed, for example `Self` in Swift.
+   */
+  string getStaticSelfName() { none() }
 }
 
 /** Holds if `member` is an instance member. */

unified/ql/lib/codeql/unified/internal/NameBindingPluginSwift.qll

@@ -44,6 +44,8 @@ class NameBindingPluginSwift extends NameBindingPlugin {
     callable = any(ClassLikeDeclaration cls).getAMember() and
     result = "self"
   }
+
+  override string getStaticSelfName() { result = "Self" }
 }
 
 /** Holds if `node` is in a context where a bare name node should be seen as a reference rather than a declaration. */

unified/ql/lib/codeql/unified/internal/StaticNameBinding.qll

@@ -210,6 +210,12 @@ predicate storeStep(NameBindingNode node1, string name, NameBindingNode node2) {
   )
   or
   FolderHeuristic::storeStep(node1, name, node2)
+  or
+  exists(ClassLikeDeclaration cls |
+    name = any(NameBindingPlugin p).getStaticSelfName() and
+    node1.isIdentifier(cls.getNameNode()) and
+    node2.isStaticMemberNamespace(cls)
+  )
 }
 
 predicate valueStep(NameBindingNode node1, NameBindingNode node2) {

unified/ql/test/library-tests/static-name-binding/explicit-instance-field-access.swift

@@ -8,7 +8,7 @@ private class A {
     static let y = 456 // name=A.type.y
 
     func getY1() {
-        return Self.y // $ MISSING: access=A access=A.type.y
+        return Self.y // $ access=A access=A.type.y
     }
 
     static func getY2() {
@@ -30,7 +30,7 @@ private class B : A { // $ access=A
     }
 
     func getY3() {
-        return Self.y // $ MISSING: access=B access=A.type.y
+        return Self.y // $ access=B access=A.type.y
     }
 
     static func getY4() {