handle updates of parameters

src/ast/nodes/UpdateExpression.js

@@ -14,7 +14,10 @@ export default class UpdateExpression extends Node {
 		if ( subject.type === 'Identifier' ) {
 			const declaration = scope.findDeclaration( subject.name );
 			declaration.isReassigned = true;
-			declaration.possibleValues.add( NUMBER );
+
+			if ( declaration.possibleValues ) {
+				declaration.possibleValues.add( NUMBER );
+			}
 		}
 
 		super.bind( scope );

test/function/reassign-parameter/_config.js

@@ -0,0 +1,3 @@
+module.exports = {
+	description: 'parameters can be reassigned/updated'
+};

test/function/reassign-parameter/main.js

@@ -0,0 +1,7 @@
+function numbers ( i ) {
+	var array = new Array( i );
+	while ( i-- ) array[i] = i + 1;
+	return array;
+}
+
+assert.deepEqual( numbers( 5 ), [ 1, 2, 3, 4, 5 ] );