track side-effects to default exports - fixes #733, sort of

src/utils/run.js

@@ -104,7 +104,7 @@ export default function run ( node, scope, statement, strongDependencies, force
 				} else {
 					declaration = statement.module.trace( subject.name );
 
-					if ( !declaration || declaration.isExternal || declaration.isUsed ) {
+					if ( !declaration || declaration.isExternal || declaration.isUsed || ( declaration.original && declaration.original.isUsed ) ) {
 						hasSideEffect = true;
 					}
 				}

test/function/export-two-ways-default/bar.js

@@ -1,6 +1,6 @@
 import { X } from './x.js'; // import X works
 
 X.prototype.bar = function () {
-	console.log( 'bar' );
+	this.didBar = true;
 	return this;
 };

test/function/export-two-ways-default/foo.js

@@ -1,7 +1,7 @@
 export function X () {}
 
 X.prototype.foo = function () {
-	console.log( 'foo' );
+	this.didFoo = true;
 	return this;
 };
 

test/function/export-two-ways-default/main.js

@@ -1,4 +1,6 @@
 import { x } from './x.js';
 import './bar.js';
 
-x().foo().bar();
+var result = x().foo().bar();
+assert.ok( result.didFoo );
+assert.ok( result.didBar );