add some dev mode checking

src/compile/Component.ts

@@ -201,10 +201,13 @@ export default class Component {
 			return sigil.slice(1) + name;
 		});
 
-		const importedHelpers = Array.from(helpers).concat('SvelteComponent').sort().map(name => {
-			const alias = this.alias(name);
-			return { name, alias };
-		});
+		const importedHelpers = Array.from(helpers)
+			.concat(options.dev ? '$$ComponentDev' : '$$Component')
+			.sort()
+			.map(name => {
+				const alias = this.alias(name);
+				return { name, alias };
+			});
 
 		const sharedPath = options.shared || 'svelte/internal.js';
 

src/compile/render-dom/index.ts

@@ -110,8 +110,16 @@ export default function dom(
 			component.event_handlers.map(handler => handler.name)
 		);
 
+		const superclass = component.alias(options.dev ? '$$ComponentDev' : '$$Component');
+
+		if (options.dev && !options.hydratable) {
+			block.builders.hydrate.addLine(
+				'throw new Error("options.hydrate only works if the component was compiled with the `hydratable: true` option");'
+			);
+		}
+
 		builder.addBlock(deindent`
-			class ${name} extends @SvelteComponent {
+			class ${name} extends ${superclass} {
 				$$init($$make_dirty) {
 					${component.javascript || component.exports.map(x => `let ${x.name};`)}
 

src/internal/Component.js

@@ -3,7 +3,7 @@ import { set_current_component } from './lifecycle.js'
 import { run_all } from './utils.js';
 import { blankObject } from './utils.js';
 
-export class SvelteComponent {
+export class $$Component {
 	constructor(options) {
 		this.$$onprops = [];
 		this.$$onmount = [];
@@ -105,4 +105,14 @@ export class SvelteComponent {
 		run_all(this.$$onupdate);
 		this.$$dirty = null;
 	}
+}
+
+export class $$ComponentDev extends $$Component {
+	constructor(options) {
+		if (!options || !options.target) {
+			throw new Error(`'target' is a required option`);
+		}
+
+		super(options);
+	}
 }

src/internal/index.js

@@ -8,4 +8,4 @@ export * from './spread.js';
 export * from './ssr.js';
 export * from './transitions.js';
 export * from './utils.js';
-export * from './SvelteComponent.js';
+export * from './Component.js';

test/runtime/index.js

@@ -3,6 +3,8 @@ import chalk from 'chalk';
 import * as path from "path";
 import * as fs from "fs";
 import * as acorn from "acorn";
+import { rollup } from 'rollup';
+import virtual from 'rollup-plugin-virtual';
 import { transitionManager } from "../../internal.js";
 
 import {
@@ -213,35 +215,52 @@ describe.only("runtime", () => {
 		runTest(dir, internal, true);
 	});
 
-	it("fails if options.target is missing in dev mode", () => {
-		const { js } = svelte$.compile(`<div></div>`, {
-			format: "iife",
+	async function create_component(src = '<div></div>') {
+		const { js } = svelte$.compile(src, {
+			format: "es", // TODO change this to esm
 			name: "SvelteComponent",
 			dev: true
 		});
 
-		const SvelteComponent = eval(
-			`(function () { ${js.code}; return SvelteComponent; }())`
+		const bundle = await rollup({
+			input: 'main.js',
+			plugins: [
+				virtual({
+					'main.js': js.code
+				}),
+				{
+					resolveId: (importee, importer) => {
+						if (importee.startsWith('svelte/')) {
+							return importee.replace('svelte', process.cwd());
+						}
+					}
+				}
+			]
+		});
+
+		const result = await bundle.generate({
+			format: 'iife',
+			name: 'App'
+		});
+
+		return eval(
+			`(function () { ${result.code}; return App; }())`
 		);
+	}
+
+	it("fails if options.target is missing in dev mode", async () => {
+		const App = await create_component();
 
 		assert.throws(() => {
-			new SvelteComponent();
+			new App();
 		}, /'target' is a required option/);
 	});
 
-	it("fails if options.hydrate is true but the component is non-hydratable", () => {
-		const { js } = svelte$.compile(`<div></div>`, {
-			format: "iife",
-			name: "SvelteComponent",
-			dev: true
-		});
-
-		const SvelteComponent = eval(
-			`(function () { ${js.code}; return SvelteComponent; }())`
-		);
+	it("fails if options.hydrate is true but the component is non-hydratable", async () => {
+		const App = await create_component();
 
 		assert.throws(() => {
-			new SvelteComponent({
+			new App({
 				target: {},
 				hydrate: true
 			});