IE 11 support

package.json

@@ -21,7 +21,7 @@
   "dependencies": {
     "html-minifier": "^4.0.0",
     "http-link-header": "^1.0.2",
-    "shimport": "^1.0.1",
+    "shimport": "^2.0.3",
     "source-map": "^0.6.1",
     "sourcemap-codec": "^1.4.6",
     "string-hash": "^1.1.3"

src/core/create_compilers/RollupCompiler.ts

@@ -19,10 +19,10 @@ const stderr = console.error.bind(console);
 let rollup: any;
 
 const inject_styles = `
-export default files => {
-	return Promise.all(files.map(file => new Promise((fulfil, reject) => {
-		const href = new URL(file, import.meta.url);
-		let link = document.querySelector('link[rel=stylesheet][href="' + href + '"]');
+export default function(files) {
+	return Promise.all(files.map(function(file) { return new Promise(function(fulfil, reject) {
+		var href = new URL(file, import.meta.url);
+		var link = document.querySelector('link[rel=stylesheet][href="' + href + '"]');
 		if (!link) {
 			link = document.createElement('link');
 			link.rel = 'stylesheet';
@@ -32,10 +32,10 @@ export default files => {
 		if (link.sheet) {
 			fulfil();
 		} else {
-			link.onload = () => fulfil();
+			link.onload = function() { return fulfil() };
 			link.onerror = reject;
 		}
-	})));
+	})}));
 };`.trim();
 
 const get_entry_point_output_chunk = (bundle: OutputBundle, entry_point?: string) => {
@@ -130,7 +130,7 @@ export default class RollupCompiler {
 				if (targetModuleId) {
 					return {
 						left: 'Promise.all([import(',
-						right: `), ___SAPPER_CSS_INJECTION___${Buffer.from(targetModuleId).toString('hex')}___]).then(x => x[0])`
+						right: `), ___SAPPER_CSS_INJECTION___${Buffer.from(targetModuleId).toString('hex')}___]).then(function(x) { return x[0]; })`
 					};
 				} else {
 					return {