dont rewrite var foo as var exports.foo

src/Module.js

@@ -641,7 +641,11 @@ export default class Module {
 
 			// split up/remove var declarations as necessary
 			if ( statement.node.isSynthetic ) {
-				magicString.insert( statement.start, `${statement.node.kind} ` );
+				// insert `var/let/const` if necessary
+				if ( !allBundleExports[ statement.node.declarations[0].id.name ] ) {
+					magicString.insert( statement.start, `${statement.node.kind} ` );
+				}
+
 				magicString.overwrite( statement.end, statement.next, ';\n' ); // TODO account for trailing newlines
 			}
 

test/function/export-and-import-reference-share-var/_config.js

@@ -0,0 +1,11 @@
+var assert = require( 'assert' );
+
+module.exports = {
+	description: 'allows export and import reference to share name',
+	exports: function ( exports ) {
+		assert.equal( exports.b, 9 );
+	},
+	solo: true
+};
+
+// adapted from es6-module-transpiler

test/function/export-and-import-reference-share-var/foo.js

@@ -0,0 +1,2 @@
+export var a = 1;
+assert.equal(a, 1);

test/function/export-and-import-reference-share-var/main.js

@@ -0,0 +1,13 @@
+import { a } from './foo';
+
+// This variable declaration is going to be altered because `b` needs to be
+// re-written. We need to make sure that the `a` re-writing and the unaffected
+// `c` declarator are not being clobbered by that alteration.
+var a_ = a, b = 9, c = 'c';
+
+assert.equal(a, 1);
+assert.equal(a_, 1);
+assert.equal(b, 9);
+assert.equal(c, 'c');
+
+export { b };