unified: Add tests and handle capture-declaration scoping

Author: asgerf

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

@@ -168,6 +168,11 @@ private module LocalNameBindingInput implements LocalNameBindingInputSig<Locatio
 
   private class LocalVariableDeclarationSiblingShadowingDecl extends SiblingShadowingDecl instanceof LocalVariableDeclaration
   {
+    LocalVariableDeclarationSiblingShadowingDecl() {
+      // Capture-declarations act as local variables, but are not sibling-shadowing
+      not this = any(FunctionExpr e).getACaptureDeclaration()
+    }
+
     override Expr getPattern() { result = LocalVariableDeclaration.super.getPattern() }
 
     override AstNode getRhs() { result = LocalVariableDeclaration.super.getValue() }

unified/ql/test/library-tests/local-name-binding/self_access.swift

@@ -0,0 +1,33 @@
+class C {
+    func t1() { // implicit-self=t1.self
+        print(self) // $ access=t1.self
+    }
+
+    var instanceField = 123;
+
+    func t2() { // implicit-self=t2.self
+        print(instanceField) // $ access=instanceField implicit-qualifier=t2.self
+    }
+
+    func t3() { // implicit-self=t3.self
+        foo(123) { [self] in // name=closure.self
+            print(self) // $ access=closure.self
+            print(instanceField) // $ access=instanceField implicit-qualifier=closure.self
+        }
+    }
+
+    func t4() { // implicit-self=t4.self
+        foo(123) { [weak self] in // name=weak.self
+            // Here, 'self' is an Option<C> referring to .some(<outer self>) if it
+            // has not been GC'ed yet. Swift does not allow unqualified self access here.
+
+            print(self) // $ access=weak.self
+
+            // Unwrap the 'self' optional to get a strong reference.
+            guard let self else { return } // $ access=weak.self // name=guarded.self
+
+            print(self) // $ access=guarded.self
+            print(instanceField) // $ access=instanceField implicit-qualifier=guarded.self
+        }
+    }
+}