rename functions with args by the same name (fixes #32)

src/Statement.js

@@ -315,15 +315,20 @@ export default class Statement {
 					let newNames = blank();
 					let hasReplacements;
 
-					keys( names ).forEach( key => {
+					// special case = function foo ( foo ) {...}
-						if ( !scope.declarations[ key ] ) {
+					if ( node.id && names[ node.id.name ] && scope.declarations[ node.id.name ] ) {
-							newNames[ key ] = names[ key ];
+						magicString.overwrite( node.id.start, node.id.end, names[ node.id.name ] );
+					}
+
+					keys( names ).forEach( name => {
+						if ( !scope.declarations[ name ] ) {
+							newNames[ name ] = names[ name ];
 							hasReplacements = true;
 						}
 					});
 
 					deshadowList.forEach( name => {
-						if ( ~scope.declarations[ name ] ) {
+						if ( ~scope.declarations[ name ] ) { // TODO is this right? no indexOf?
 							newNames[ name ] = name + '$$'; // TODO better mechanism
 							hasReplacements = true;
 						}

test/function/renamed-arguments/_config.js

@@ -0,0 +1,10 @@
+var assert = require( 'assert' );
+
+module.exports = {
+	description: 'function arguments are renamed as appropriate (#32)',
+	exports: function ( exports ) {
+		var obj = {};
+		assert.strictEqual( exports.foo(), 42 );
+		assert.strictEqual( exports.bar( obj ), obj );
+	}
+};

test/function/renamed-arguments/bar.js

@@ -0,0 +1,5 @@
+function thing ( thing ) {
+	return thing;
+}
+
+export default thing;

test/function/renamed-arguments/foo.js

@@ -0,0 +1,5 @@
+function thing () {
+	return 42;
+}
+
+export default thing;

test/function/renamed-arguments/main.js

@@ -0,0 +1,7 @@
+import foo from './foo';
+import bar from './bar';
+
+export {
+	foo,
+	bar
+};