Make sure property mutations on function arguments are not lost

src/ast/nodes/CallExpression.ts

@@ -1,11 +1,11 @@
 import CallOptions from '../CallOptions';
 import ExecutionPathOptions from '../ExecutionPathOptions';
 import SpreadElement from './SpreadElement';
-import { isIdentifier } from './Identifier';
+import Identifier from './Identifier';
 import { ForEachReturnExpressionCallback, SomeReturnExpressionCallback } from './shared/Expression';
 import * as NodeType from './NodeType';
 import { ExpressionNode, NodeBase } from './shared/Node';
-import { ObjectPath } from '../values';
+import { ObjectPath, UNKNOWN_KEY } from '../values';
 
 export default class CallExpression extends NodeBase {
 	type: NodeType.tCallExpression;
@@ -16,7 +16,7 @@ export default class CallExpression extends NodeBase {
 
 	bind() {
 		super.bind();
-		if (isIdentifier(this.callee)) {
+		if (this.callee instanceof Identifier) {
 			const variable = this.scope.findVariable(this.callee.name);
 
 			if (variable.isNamespace) {
@@ -40,6 +40,10 @@ export default class CallExpression extends NodeBase {
 				);
 			}
 		}
+		for (const argument of this.arguments) {
+			// This will make sure all properties of parameters behave as "unknown"
+			argument.reassignPath([UNKNOWN_KEY], ExecutionPathOptions.create());
+		}
 	}
 
 	forEachReturnExpressionWhenCalledAtPath(

src/ast/variables/LocalVariable.ts

@@ -97,6 +97,7 @@ export default class LocalVariable extends Variable {
 		callOptions: CallOptions,
 		options: ExecutionPathOptions
 	) {
+		// The "included && path.length > 0" check is needed for mutating methods on arrays
 		if (path.length > MAX_PATH_DEPTH || (this.included && path.length > 0)) return true;
 		return (
 			this.reassignments.isPathReassigned(path) ||

test/function/samples/associate-function-return-values-5/_config.js

@@ -0,0 +1,8 @@
+var assert = require('assert');
+
+module.exports = {
+	description: 'Associates value mutations across return values',
+	exports: function(exports) {
+		assert.equal(exports.bar, 'present');
+	}
+};

test/function/samples/associate-function-return-values-5/main.js

@@ -0,0 +1,14 @@
+const foo = {value: false};
+const exported = {};
+
+function getFoo() {
+  return foo;
+}
+
+getFoo().value = true;
+
+if (foo.value) {
+	exported.bar = 'present'
+}
+
+export default exported;

test/function/samples/reassign-parameter-property/_config.js

@@ -0,0 +1,3 @@
+module.exports = {
+	description: 'track reassignments of properties of function parameters'
+};

test/function/samples/reassign-parameter-property/main.js

@@ -0,0 +1,17 @@
+const obj = {
+	flag: false
+};
+
+function reassign(x) {
+	x.flag = true;
+}
+
+reassign(obj);
+
+let hasBeenReassigned = false;
+
+if (obj.flag) {
+	hasBeenReassigned = true;
+}
+
+assert.ok(hasBeenReassigned);