Merge pull request #406 from rollup/gh-403

handle a => a at top level

src/ast/isReference.js

@@ -4,6 +4,11 @@ export default function isReference ( node, parent ) {
 	}
 
 	if ( node.type === 'Identifier' ) {
+		// the only time we could have an identifier node without a parent is
+		// if it's the entire body of a function without a block statement –
+		// i.e. an arrow function expression like `a => a`
+		if ( !parent ) return true;
+
 		// TODO is this right?
 		if ( parent.type === 'MemberExpression' ) return parent.computed || node === parent.object;
 

test/function/top-level-arrow-function/_config.js

@@ -0,0 +1,4 @@
+module.exports = {
+	description: 'handles naked return value from top-level arrow function expression (#403)',
+	babel: true
+};

test/function/top-level-arrow-function/main.js

@@ -0,0 +1,2 @@
+const f = a => a;
+assert.equal( f( 42 ), 42 );