diff --git a/test/js/samples/action-custom-event-handler/expected.js b/test/js/samples/action-custom-event-handler/expected.js
index 5ed38de87c..f4120f5b50 100644
--- a/test/js/samples/action-custom-event-handler/expected.js
+++ b/test/js/samples/action-custom-event-handler/expected.js
@@ -24,7 +24,7 @@ function create_fragment(ctx) {
 			foo_action = foo.call(null, button, ctx[1]) || ({});
 		},
 		p(ctx, changed) {
-			if (is_function(foo_action.update) && changed.bar) foo_action.update.call(null, ctx[1]);
+			if (is_function(foo_action.update) && changed & 1) foo_action.update.call(null, ctx[1]);
 		},
 		i: noop,
 		o: noop,
diff --git a/test/js/samples/bind-online/expected.js b/test/js/samples/bind-online/expected.js
index 278d807001..a2e0c0b89d 100644
--- a/test/js/samples/bind-online/expected.js
+++ b/test/js/samples/bind-online/expected.js
@@ -15,10 +15,7 @@ function create_fragment(ctx) {
 
 	return {
 		c() {
-			dispose = [
-				listen(window, "online", ctx[1]),
-				listen(window, "offline", ctx[1])
-			];
+			dispose = [listen(window, "online", ctx[1]), listen(window, "offline", ctx[1])];
 		},
 		m: noop,
 		p: noop,
diff --git a/test/js/samples/bind-open/expected.js b/test/js/samples/bind-open/expected.js
index f235b21f7b..d5680c0aa7 100644
--- a/test/js/samples/bind-open/expected.js
+++ b/test/js/samples/bind-open/expected.js
@@ -27,8 +27,10 @@ function create_fragment(ctx) {
 			insert(target, details, anchor);
 			details.open = ctx[0];
 		},
-		p(ctx) {
-			details.open = ctx[0];
+		p(ctx, changed) {
+			if (changed & 1) {
+				details.open = ctx[0];
+			}
 		},
 		i: noop,
 		o: noop,
@@ -43,7 +45,8 @@ function instance($$self, $$props, $$invalidate) {
 	let { open } = $$props;
 
 	function details_toggle_handler() {
-		$$invalidate(0, open = this.open);
+		open = this.open;
+		$$invalidate(0, open);
 	}
 
 	$$self.$set = $$props => {
diff --git a/test/js/samples/bind-width-height/expected.js b/test/js/samples/bind-width-height/expected.js
index 18efcfdc08..551f05fd76 100644
--- a/test/js/samples/bind-width-height/expected.js
+++ b/test/js/samples/bind-width-height/expected.js
@@ -19,11 +19,11 @@ function create_fragment(ctx) {
 		c() {
 			div = element("div");
 			div.textContent = "some content";
-			add_render_callback(() => ctx.div_elementresize_handler.call(div));
+			add_render_callback(() => ctx[2].call(div));
 		},
 		m(target, anchor) {
 			insert(target, div, anchor);
-			div_resize_listener = add_resize_listener(div, ctx.div_elementresize_handler.bind(div));
+			div_resize_listener = add_resize_listener(div, ctx[2].bind(div));
 		},
 		p: noop,
 		i: noop,
@@ -42,22 +42,22 @@ function instance($$self, $$props, $$invalidate) {
 	function div_elementresize_handler() {
 		w = this.offsetWidth;
 		h = this.offsetHeight;
-		$$invalidate("w", w);
-		$$invalidate("h", h);
+		$$invalidate(0, w);
+		$$invalidate(1, h);
 	}
 
 	$$self.$set = $$props => {
-		if ("w" in $$props) $$invalidate("w", w = $$props.w);
-		if ("h" in $$props) $$invalidate("h", h = $$props.h);
+		if ("w" in $$props) $$invalidate(0, w = $$props.w);
+		if ("h" in $$props) $$invalidate(1, h = $$props.h);
 	};
 
-	return { w, h, div_elementresize_handler };
+	return [w, h, div_elementresize_handler];
 }
 
 class Component extends SvelteComponent {
 	constructor(options) {
 		super();
-		init(this, options, instance, create_fragment, safe_not_equal, { w: 0, h: 0 });
+		init(this, options, instance, create_fragment, safe_not_equal, { w: 0, h: 1 });
 	}
 }
 
diff --git a/test/js/samples/bindings-readonly-order/expected.js b/test/js/samples/bindings-readonly-order/expected.js
index 04eff699f8..99078890f0 100644
--- a/test/js/samples/bindings-readonly-order/expected.js
+++ b/test/js/samples/bindings-readonly-order/expected.js
@@ -26,11 +26,7 @@ function create_fragment(ctx) {
 			input1 = element("input");
 			attr(input0, "type", "file");
 			attr(input1, "type", "file");
-
-			dispose = [
-				listen(input0, "change", ctx.input0_change_handler),
-				listen(input1, "change", ctx.input1_change_handler)
-			];
+			dispose = [listen(input0, "change", ctx[1]), listen(input1, "change", ctx[2])];
 		},
 		m(target, anchor) {
 			insert(target, input0, anchor);
@@ -54,23 +50,19 @@ function instance($$self, $$props, $$invalidate) {
 
 	function input0_change_handler() {
 		files = this.files;
-		$$invalidate("files", files);
+		$$invalidate(0, files);
 	}
 
 	function input1_change_handler() {
 		files = this.files;
-		$$invalidate("files", files);
+		$$invalidate(0, files);
 	}
 
 	$$self.$set = $$props => {
-		if ("files" in $$props) $$invalidate("files", files = $$props.files);
+		if ("files" in $$props) $$invalidate(0, files = $$props.files);
 	};
 
-	return {
-		files,
-		input0_change_handler,
-		input1_change_handler
-	};
+	return [files, input0_change_handler, input1_change_handler];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/capture-inject-dev-only/expected.js b/test/js/samples/capture-inject-dev-only/expected.js
index ee2f6d0dc9..c1c81a1c42 100644
--- a/test/js/samples/capture-inject-dev-only/expected.js
+++ b/test/js/samples/capture-inject-dev-only/expected.js
@@ -25,23 +25,23 @@ function create_fragment(ctx) {
 	return {
 		c() {
 			p = element("p");
-			t0 = text(ctx.foo);
+			t0 = text(ctx[0]);
 			t1 = space();
 			input = element("input");
-			dispose = listen(input, "input", ctx.input_input_handler);
+			dispose = listen(input, "input", ctx[1]);
 		},
 		m(target, anchor) {
 			insert(target, p, anchor);
 			append(p, t0);
 			insert(target, t1, anchor);
 			insert(target, input, anchor);
-			set_input_value(input, ctx.foo);
+			set_input_value(input, ctx[0]);
 		},
-		p(changed, ctx) {
-			if (changed.foo) set_data(t0, ctx.foo);
+		p(ctx, changed) {
+			if (changed & 1) set_data(t0, ctx[0]);
 
-			if (changed.foo && input.value !== ctx.foo) {
-				set_input_value(input, ctx.foo);
+			if (changed & 1 && input.value !== ctx[0]) {
+				set_input_value(input, ctx[0]);
 			}
 		},
 		i: noop,
@@ -60,10 +60,10 @@ function instance($$self, $$props, $$invalidate) {
 
 	function input_input_handler() {
 		foo = this.value;
-		$$invalidate("foo", foo);
+		$$invalidate(0, foo);
 	}
 
-	return { foo, input_input_handler };
+	return [foo, input_input_handler];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/collapses-text-around-comments/expected.js b/test/js/samples/collapses-text-around-comments/expected.js
index 5fb7aaef15..0819a0de01 100644
--- a/test/js/samples/collapses-text-around-comments/expected.js
+++ b/test/js/samples/collapses-text-around-comments/expected.js
@@ -27,15 +27,15 @@ function create_fragment(ctx) {
 	return {
 		c() {
 			p = element("p");
-			t = text(ctx.foo);
+			t = text(ctx[0]);
 			attr(p, "class", "svelte-1a7i8ec");
 		},
 		m(target, anchor) {
 			insert(target, p, anchor);
 			append(p, t);
 		},
-		p(changed, ctx) {
-			if (changed.foo) set_data(t, ctx.foo);
+		p(ctx, changed) {
+			if (changed & 1) set_data(t, ctx[0]);
 		},
 		i: noop,
 		o: noop,
@@ -49,10 +49,10 @@ function instance($$self, $$props, $$invalidate) {
 	let { foo = 42 } = $$props;
 
 	$$self.$set = $$props => {
-		if ("foo" in $$props) $$invalidate("foo", foo = $$props.foo);
+		if ("foo" in $$props) $$invalidate(0, foo = $$props.foo);
 	};
 
-	return { foo };
+	return [foo];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/component-static-array/expected.js b/test/js/samples/component-static-array/expected.js
index b89ee46764..7948ecd171 100644
--- a/test/js/samples/component-static-array/expected.js
+++ b/test/js/samples/component-static-array/expected.js
@@ -13,7 +13,7 @@ import {
 
 function create_fragment(ctx) {
 	let current;
-	const nested = new ctx.Nested({ props: { foo: [1, 2, 3] } });
+	const nested = new ctx[0]({ props: { foo: [1, 2, 3] } });
 
 	return {
 		c() {
@@ -41,7 +41,7 @@ function create_fragment(ctx) {
 
 function instance($$self) {
 	const Nested = window.Nested;
-	return { Nested };
+	return [Nested];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/component-static-immutable/expected.js b/test/js/samples/component-static-immutable/expected.js
index 17b42a4a43..80d531b793 100644
--- a/test/js/samples/component-static-immutable/expected.js
+++ b/test/js/samples/component-static-immutable/expected.js
@@ -13,7 +13,7 @@ import {
 
 function create_fragment(ctx) {
 	let current;
-	const nested = new ctx.Nested({ props: { foo: "bar" } });
+	const nested = new ctx[0]({ props: { foo: "bar" } });
 
 	return {
 		c() {
@@ -41,7 +41,7 @@ function create_fragment(ctx) {
 
 function instance($$self) {
 	const Nested = window.Nested;
-	return { Nested };
+	return [Nested];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/component-static-immutable2/expected.js b/test/js/samples/component-static-immutable2/expected.js
index 17b42a4a43..80d531b793 100644
--- a/test/js/samples/component-static-immutable2/expected.js
+++ b/test/js/samples/component-static-immutable2/expected.js
@@ -13,7 +13,7 @@ import {
 
 function create_fragment(ctx) {
 	let current;
-	const nested = new ctx.Nested({ props: { foo: "bar" } });
+	const nested = new ctx[0]({ props: { foo: "bar" } });
 
 	return {
 		c() {
@@ -41,7 +41,7 @@ function create_fragment(ctx) {
 
 function instance($$self) {
 	const Nested = window.Nested;
-	return { Nested };
+	return [Nested];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/component-static-var/expected.js b/test/js/samples/component-static-var/expected.js
index 29c585744e..fcbc130676 100644
--- a/test/js/samples/component-static-var/expected.js
+++ b/test/js/samples/component-static-var/expected.js
@@ -26,7 +26,7 @@ function create_fragment(ctx) {
 	let current;
 	let dispose;
 	const foo = new Foo({ props: { x: y } });
-	const bar = new Bar({ props: { x: ctx.z } });
+	const bar = new Bar({ props: { x: ctx[0] } });
 
 	return {
 		c() {
@@ -35,7 +35,7 @@ function create_fragment(ctx) {
 			create_component(bar.$$.fragment);
 			t1 = space();
 			input = element("input");
-			dispose = listen(input, "input", ctx.input_input_handler);
+			dispose = listen(input, "input", ctx[1]);
 		},
 		m(target, anchor) {
 			mount_component(foo, target, anchor);
@@ -43,16 +43,16 @@ function create_fragment(ctx) {
 			mount_component(bar, target, anchor);
 			insert(target, t1, anchor);
 			insert(target, input, anchor);
-			set_input_value(input, ctx.z);
+			set_input_value(input, ctx[0]);
 			current = true;
 		},
-		p(changed, ctx) {
+		p(ctx, changed) {
 			const bar_changes = {};
-			if (changed.z) bar_changes.x = ctx.z;
+			if (changed & 1) bar_changes.x = ctx[0];
 			bar.$set(bar_changes);
 
-			if (changed.z && input.value !== ctx.z) {
-				set_input_value(input, ctx.z);
+			if (changed & 1 && input.value !== ctx[0]) {
+				set_input_value(input, ctx[0]);
 			}
 		},
 		i(local) {
@@ -84,10 +84,10 @@ function instance($$self, $$props, $$invalidate) {
 
 	function input_input_handler() {
 		z = this.value;
-		$$invalidate("z", z);
+		$$invalidate(0, z);
 	}
 
-	return { z, input_input_handler };
+	return [z, input_input_handler];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/component-static/expected.js b/test/js/samples/component-static/expected.js
index 16d9ea9c4c..c242bf0bf5 100644
--- a/test/js/samples/component-static/expected.js
+++ b/test/js/samples/component-static/expected.js
@@ -13,7 +13,7 @@ import {
 
 function create_fragment(ctx) {
 	let current;
-	const nested = new ctx.Nested({ props: { foo: "bar" } });
+	const nested = new ctx[0]({ props: { foo: "bar" } });
 
 	return {
 		c() {
@@ -41,7 +41,7 @@ function create_fragment(ctx) {
 
 function instance($$self) {
 	const Nested = window.Nested;
-	return { Nested };
+	return [Nested];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/component-store-access-invalidate/expected.js b/test/js/samples/component-store-access-invalidate/expected.js
index b3eedd3d6e..b31c1e1a6a 100644
--- a/test/js/samples/component-store-access-invalidate/expected.js
+++ b/test/js/samples/component-store-access-invalidate/expected.js
@@ -22,14 +22,14 @@ function create_fragment(ctx) {
 	return {
 		c() {
 			h1 = element("h1");
-			t = text(ctx.$foo);
+			t = text(ctx[1]);
 		},
 		m(target, anchor) {
 			insert(target, h1, anchor);
 			append(h1, t);
 		},
-		p(changed, ctx) {
-			if (changed.$foo) set_data(t, ctx.$foo);
+		p(ctx, changed) {
+			if (changed & 2) set_data(t, ctx[1]);
 		},
 		i: noop,
 		o: noop,
@@ -42,8 +42,8 @@ function create_fragment(ctx) {
 function instance($$self, $$props, $$invalidate) {
 	let $foo;
 	const foo = writable(0);
-	component_subscribe($$self, foo, value => $$invalidate("$foo", $foo = value));
-	return { foo, $foo };
+	component_subscribe($$self, foo, value => $$invalidate(1, $foo = value));
+	return [foo, $foo];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/component-store-file-invalidate/expected.js b/test/js/samples/component-store-file-invalidate/expected.js
index a4d7ad5c10..d2fb3d0be4 100644
--- a/test/js/samples/component-store-file-invalidate/expected.js
+++ b/test/js/samples/component-store-file-invalidate/expected.js
@@ -11,13 +11,13 @@ import { count } from "./store.js";
 
 function instance($$self, $$props, $$invalidate) {
 	let $count;
-	component_subscribe($$self, count, $$value => $$invalidate("$count", $count = $$value));
+	component_subscribe($$self, count, $$value => $$invalidate(1, $count = $$value));
 
 	function increment() {
 		set_store_value(count, $count++, $count);
 	}
 
-	return { increment };
+	return [increment];
 }
 
 class Component extends SvelteComponent {
@@ -27,7 +27,7 @@ class Component extends SvelteComponent {
 	}
 
 	get increment() {
-		return this.$$.ctx.increment;
+		return this.$$.ctx[0];
 	}
 }
 
diff --git a/test/js/samples/component-store-reassign-invalidate/expected.js b/test/js/samples/component-store-reassign-invalidate/expected.js
index 890e28f79c..a36c37577d 100644
--- a/test/js/samples/component-store-reassign-invalidate/expected.js
+++ b/test/js/samples/component-store-reassign-invalidate/expected.js
@@ -27,11 +27,11 @@ function create_fragment(ctx) {
 	return {
 		c() {
 			h1 = element("h1");
-			t0 = text(ctx.$foo);
+			t0 = text(ctx[1]);
 			t1 = space();
 			button = element("button");
 			button.textContent = "reset";
-			dispose = listen(button, "click", ctx.click_handler);
+			dispose = listen(button, "click", ctx[2]);
 		},
 		m(target, anchor) {
 			insert(target, h1, anchor);
@@ -39,8 +39,8 @@ function create_fragment(ctx) {
 			insert(target, t1, anchor);
 			insert(target, button, anchor);
 		},
-		p(changed, ctx) {
-			if (changed.$foo) set_data(t0, ctx.$foo);
+		p(ctx, changed) {
+			if (changed & 2) set_data(t0, ctx[1]);
 		},
 		i: noop,
 		o: noop,
@@ -56,13 +56,13 @@ function create_fragment(ctx) {
 function instance($$self, $$props, $$invalidate) {
 	let $foo,
 		$$unsubscribe_foo = noop,
-		$$subscribe_foo = () => ($$unsubscribe_foo(), $$unsubscribe_foo = subscribe(foo, $$value => $$invalidate("$foo", $foo = $$value)), foo);
+		$$subscribe_foo = () => ($$unsubscribe_foo(), $$unsubscribe_foo = subscribe(foo, $$value => $$invalidate(1, $foo = $$value)), foo);
 
 	$$self.$$.on_destroy.push(() => $$unsubscribe_foo());
 	let foo = writable(0);
 	$$subscribe_foo();
-	const click_handler = () => $$subscribe_foo($$invalidate("foo", foo = writable(0)));
-	return { foo, $foo, click_handler };
+	const click_handler = () => $$subscribe_foo($$invalidate(0, foo = writable(0)));
+	return [foo, $foo, click_handler];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/computed-collapsed-if/expected.js b/test/js/samples/computed-collapsed-if/expected.js
index 4d3954358e..8e5964f8a6 100644
--- a/test/js/samples/computed-collapsed-if/expected.js
+++ b/test/js/samples/computed-collapsed-if/expected.js
@@ -13,24 +13,24 @@ function instance($$self, $$props, $$invalidate) {
 	}
 
 	$$self.$set = $$props => {
-		if ("x" in $$props) $$invalidate("x", x = $$props.x);
+		if ("x" in $$props) $$invalidate(0, x = $$props.x);
 	};
 
-	return { x, a, b };
+	return [x, a, b];
 }
 
 class Component extends SvelteComponent {
 	constructor(options) {
 		super();
-		init(this, options, instance, null, safe_not_equal, { x: 0, a: 0, b: 0 });
+		init(this, options, instance, null, safe_not_equal, { x: 0, a: 1, b: 2 });
 	}
 
 	get a() {
-		return this.$$.ctx.a;
+		return this.$$.ctx[1];
 	}
 
 	get b() {
-		return this.$$.ctx.b;
+		return this.$$.ctx[2];
 	}
 }
 
diff --git a/test/js/samples/data-attribute/expected.js b/test/js/samples/data-attribute/expected.js
index 674be31867..86ecc37166 100644
--- a/test/js/samples/data-attribute/expected.js
+++ b/test/js/samples/data-attribute/expected.js
@@ -22,16 +22,16 @@ function create_fragment(ctx) {
 			t = space();
 			div1 = element("div");
 			attr(div0, "data-foo", "bar");
-			attr(div1, "data-foo", ctx.bar);
+			attr(div1, "data-foo", ctx[0]);
 		},
 		m(target, anchor) {
 			insert(target, div0, anchor);
 			insert(target, t, anchor);
 			insert(target, div1, anchor);
 		},
-		p(changed, ctx) {
-			if (changed.bar) {
-				attr(div1, "data-foo", ctx.bar);
+		p(ctx, changed) {
+			if (changed & 1) {
+				attr(div1, "data-foo", ctx[0]);
 			}
 		},
 		i: noop,
@@ -48,10 +48,10 @@ function instance($$self, $$props, $$invalidate) {
 	let { bar } = $$props;
 
 	$$self.$set = $$props => {
-		if ("bar" in $$props) $$invalidate("bar", bar = $$props.bar);
+		if ("bar" in $$props) $$invalidate(0, bar = $$props.bar);
 	};
 
-	return { bar };
+	return [bar];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/debug-empty/expected.js b/test/js/samples/debug-empty/expected.js
index b545823c57..572c33d732 100644
--- a/test/js/samples/debug-empty/expected.js
+++ b/test/js/samples/debug-empty/expected.js
@@ -28,7 +28,7 @@ function create_fragment(ctx) {
 		c: function create() {
 			h1 = element("h1");
 			t0 = text("Hello ");
-			t1 = text(ctx.name);
+			t1 = text(ctx[0]);
 			t2 = text("!");
 			t3 = space();
 			debugger;
@@ -44,8 +44,8 @@ function create_fragment(ctx) {
 			append_dev(h1, t2);
 			insert_dev(target, t3, anchor);
 		},
-		p: function update(changed, ctx) {
-			if (changed.name) set_data_dev(t1, ctx.name);
+		p: function update(ctx, changed) {
+			if (changed & 1) set_data_dev(t1, ctx[0]);
 			debugger;
 		},
 		i: noop,
@@ -76,7 +76,7 @@ function instance($$self, $$props, $$invalidate) {
 	});
 
 	$$self.$set = $$props => {
-		if ("name" in $$props) $$invalidate("name", name = $$props.name);
+		if ("name" in $$props) $$invalidate(0, name = $$props.name);
 	};
 
 	$$self.$capture_state = () => {
@@ -84,10 +84,10 @@ function instance($$self, $$props, $$invalidate) {
 	};
 
 	$$self.$inject_state = $$props => {
-		if ("name" in $$props) $$invalidate("name", name = $$props.name);
+		if ("name" in $$props) $$invalidate(0, name = $$props.name);
 	};
 
-	return { name };
+	return [name];
 }
 
 class Component extends SvelteComponentDev {
@@ -105,7 +105,7 @@ class Component extends SvelteComponentDev {
 		const { ctx } = this.$$;
 		const props = options.props || ({});
 
-		if (ctx.name === undefined && !("name" in props)) {
+		if (ctx[0] === undefined && !("name" in props)) {
 			console.warn("<Component> was created without expected prop 'name'");
 		}
 	}
diff --git a/test/js/samples/debug-foo-bar-baz-things/expected.js b/test/js/samples/debug-foo-bar-baz-things/expected.js
index 448fc82176..da59fd12fe 100644
--- a/test/js/samples/debug-foo-bar-baz-things/expected.js
+++ b/test/js/samples/debug-foo-bar-baz-things/expected.js
@@ -19,15 +19,15 @@ import {
 const file = undefined;
 
 function get_each_context(ctx, list, i) {
-	const child_ctx = Object.create(ctx);
-	child_ctx.thing = list[i];
+	const child_ctx = ctx.slice();
+	child_ctx[4] = list[i];
 	return child_ctx;
 }
 
 // (8:0) {#each things as thing}
 function create_each_block(ctx) {
 	let span;
-	let t0_value = ctx.thing.name + "";
+	let t0_value = ctx[4].name + "";
 	let t0;
 	let t1;
 
@@ -50,10 +50,10 @@ function create_each_block(ctx) {
 			append_dev(span, t0);
 			insert_dev(target, t1, anchor);
 		},
-		p: function update(changed, ctx) {
-			if (changed.things && t0_value !== (t0_value = ctx.thing.name + "")) set_data_dev(t0, t0_value);
+		p: function update(ctx, changed) {
+			if (changed & 1 && t0_value !== (t0_value = ctx[4].name + "")) set_data_dev(t0, t0_value);
 
-			if (changed.foo || changed.bar || changed.baz || changed.things) {
+			if (changed & 15) {
 				const { foo, bar, baz, thing } = ctx;
 				console.log({ foo, bar, baz, thing });
 				debugger;
@@ -81,7 +81,7 @@ function create_fragment(ctx) {
 	let p;
 	let t1;
 	let t2;
-	let each_value = ctx.things;
+	let each_value = ctx[0];
 	let each_blocks = [];
 
 	for (let i = 0; i < each_value.length; i += 1) {
@@ -97,7 +97,7 @@ function create_fragment(ctx) {
 			t0 = space();
 			p = element("p");
 			t1 = text("foo: ");
-			t2 = text(ctx.foo);
+			t2 = text(ctx[1]);
 			add_location(p, file, 12, 0, 182);
 		},
 		l: function claim(nodes) {
@@ -113,16 +113,16 @@ function create_fragment(ctx) {
 			append_dev(p, t1);
 			append_dev(p, t2);
 		},
-		p: function update(changed, ctx) {
-			if (changed.things) {
-				each_value = ctx.things;
+		p: function update(ctx, changed) {
+			if (changed & 1) {
+				each_value = ctx[0];
 				let i;
 
 				for (i = 0; i < each_value.length; i += 1) {
 					const child_ctx = get_each_context(ctx, each_value, i);
 
 					if (each_blocks[i]) {
-						each_blocks[i].p(changed, child_ctx);
+						each_blocks[i].p(child_ctx, changed);
 					} else {
 						each_blocks[i] = create_each_block(child_ctx);
 						each_blocks[i].c();
@@ -137,7 +137,7 @@ function create_fragment(ctx) {
 				each_blocks.length = each_value.length;
 			}
 
-			if (changed.foo) set_data_dev(t2, ctx.foo);
+			if (changed & 2) set_data_dev(t2, ctx[1]);
 		},
 		i: noop,
 		o: noop,
@@ -171,10 +171,10 @@ function instance($$self, $$props, $$invalidate) {
 	});
 
 	$$self.$set = $$props => {
-		if ("things" in $$props) $$invalidate("things", things = $$props.things);
-		if ("foo" in $$props) $$invalidate("foo", foo = $$props.foo);
-		if ("bar" in $$props) $$invalidate("bar", bar = $$props.bar);
-		if ("baz" in $$props) $$invalidate("baz", baz = $$props.baz);
+		if ("things" in $$props) $$invalidate(0, things = $$props.things);
+		if ("foo" in $$props) $$invalidate(1, foo = $$props.foo);
+		if ("bar" in $$props) $$invalidate(2, bar = $$props.bar);
+		if ("baz" in $$props) $$invalidate(3, baz = $$props.baz);
 	};
 
 	$$self.$capture_state = () => {
@@ -182,19 +182,19 @@ function instance($$self, $$props, $$invalidate) {
 	};
 
 	$$self.$inject_state = $$props => {
-		if ("things" in $$props) $$invalidate("things", things = $$props.things);
-		if ("foo" in $$props) $$invalidate("foo", foo = $$props.foo);
-		if ("bar" in $$props) $$invalidate("bar", bar = $$props.bar);
-		if ("baz" in $$props) $$invalidate("baz", baz = $$props.baz);
+		if ("things" in $$props) $$invalidate(0, things = $$props.things);
+		if ("foo" in $$props) $$invalidate(1, foo = $$props.foo);
+		if ("bar" in $$props) $$invalidate(2, bar = $$props.bar);
+		if ("baz" in $$props) $$invalidate(3, baz = $$props.baz);
 	};
 
-	return { things, foo, bar, baz };
+	return [things, foo, bar, baz, null, null, null];
 }
 
 class Component extends SvelteComponentDev {
 	constructor(options) {
 		super(options);
-		init(this, options, instance, create_fragment, safe_not_equal, { things: 0, foo: 0, bar: 0, baz: 0 });
+		init(this, options, instance, create_fragment, safe_not_equal, { things: 0, foo: 1, bar: 2, baz: 3 });
 
 		dispatch_dev("SvelteRegisterComponent", {
 			component: this,
@@ -206,19 +206,19 @@ class Component extends SvelteComponentDev {
 		const { ctx } = this.$$;
 		const props = options.props || ({});
 
-		if (ctx.things === undefined && !("things" in props)) {
+		if (ctx[0] === undefined && !("things" in props)) {
 			console.warn("<Component> was created without expected prop 'things'");
 		}
 
-		if (ctx.foo === undefined && !("foo" in props)) {
+		if (ctx[1] === undefined && !("foo" in props)) {
 			console.warn("<Component> was created without expected prop 'foo'");
 		}
 
-		if (ctx.bar === undefined && !("bar" in props)) {
+		if (ctx[2] === undefined && !("bar" in props)) {
 			console.warn("<Component> was created without expected prop 'bar'");
 		}
 
-		if (ctx.baz === undefined && !("baz" in props)) {
+		if (ctx[3] === undefined && !("baz" in props)) {
 			console.warn("<Component> was created without expected prop 'baz'");
 		}
 	}
diff --git a/test/js/samples/debug-foo/expected.js b/test/js/samples/debug-foo/expected.js
index 8abfd1bae1..b9795f3d38 100644
--- a/test/js/samples/debug-foo/expected.js
+++ b/test/js/samples/debug-foo/expected.js
@@ -19,15 +19,15 @@ import {
 const file = undefined;
 
 function get_each_context(ctx, list, i) {
-	const child_ctx = Object.create(ctx);
-	child_ctx.thing = list[i];
+	const child_ctx = ctx.slice();
+	child_ctx[2] = list[i];
 	return child_ctx;
 }
 
 // (6:0) {#each things as thing}
 function create_each_block(ctx) {
 	let span;
-	let t0_value = ctx.thing.name + "";
+	let t0_value = ctx[2].name + "";
 	let t0;
 	let t1;
 
@@ -50,10 +50,10 @@ function create_each_block(ctx) {
 			append_dev(span, t0);
 			insert_dev(target, t1, anchor);
 		},
-		p: function update(changed, ctx) {
-			if (changed.things && t0_value !== (t0_value = ctx.thing.name + "")) set_data_dev(t0, t0_value);
+		p: function update(ctx, changed) {
+			if (changed & 1 && t0_value !== (t0_value = ctx[2].name + "")) set_data_dev(t0, t0_value);
 
-			if (changed.foo) {
+			if (changed & 2) {
 				const { foo } = ctx;
 				console.log({ foo });
 				debugger;
@@ -81,7 +81,7 @@ function create_fragment(ctx) {
 	let p;
 	let t1;
 	let t2;
-	let each_value = ctx.things;
+	let each_value = ctx[0];
 	let each_blocks = [];
 
 	for (let i = 0; i < each_value.length; i += 1) {
@@ -97,7 +97,7 @@ function create_fragment(ctx) {
 			t0 = space();
 			p = element("p");
 			t1 = text("foo: ");
-			t2 = text(ctx.foo);
+			t2 = text(ctx[1]);
 			add_location(p, file, 10, 0, 131);
 		},
 		l: function claim(nodes) {
@@ -113,16 +113,16 @@ function create_fragment(ctx) {
 			append_dev(p, t1);
 			append_dev(p, t2);
 		},
-		p: function update(changed, ctx) {
-			if (changed.things) {
-				each_value = ctx.things;
+		p: function update(ctx, changed) {
+			if (changed & 1) {
+				each_value = ctx[0];
 				let i;
 
 				for (i = 0; i < each_value.length; i += 1) {
 					const child_ctx = get_each_context(ctx, each_value, i);
 
 					if (each_blocks[i]) {
-						each_blocks[i].p(changed, child_ctx);
+						each_blocks[i].p(child_ctx, changed);
 					} else {
 						each_blocks[i] = create_each_block(child_ctx);
 						each_blocks[i].c();
@@ -137,7 +137,7 @@ function create_fragment(ctx) {
 				each_blocks.length = each_value.length;
 			}
 
-			if (changed.foo) set_data_dev(t2, ctx.foo);
+			if (changed & 2) set_data_dev(t2, ctx[1]);
 		},
 		i: noop,
 		o: noop,
@@ -169,8 +169,8 @@ function instance($$self, $$props, $$invalidate) {
 	});
 
 	$$self.$set = $$props => {
-		if ("things" in $$props) $$invalidate("things", things = $$props.things);
-		if ("foo" in $$props) $$invalidate("foo", foo = $$props.foo);
+		if ("things" in $$props) $$invalidate(0, things = $$props.things);
+		if ("foo" in $$props) $$invalidate(1, foo = $$props.foo);
 	};
 
 	$$self.$capture_state = () => {
@@ -178,17 +178,17 @@ function instance($$self, $$props, $$invalidate) {
 	};
 
 	$$self.$inject_state = $$props => {
-		if ("things" in $$props) $$invalidate("things", things = $$props.things);
-		if ("foo" in $$props) $$invalidate("foo", foo = $$props.foo);
+		if ("things" in $$props) $$invalidate(0, things = $$props.things);
+		if ("foo" in $$props) $$invalidate(1, foo = $$props.foo);
 	};
 
-	return { things, foo };
+	return [things, foo, null, null, null];
 }
 
 class Component extends SvelteComponentDev {
 	constructor(options) {
 		super(options);
-		init(this, options, instance, create_fragment, safe_not_equal, { things: 0, foo: 0 });
+		init(this, options, instance, create_fragment, safe_not_equal, { things: 0, foo: 1 });
 
 		dispatch_dev("SvelteRegisterComponent", {
 			component: this,
@@ -200,11 +200,11 @@ class Component extends SvelteComponentDev {
 		const { ctx } = this.$$;
 		const props = options.props || ({});
 
-		if (ctx.things === undefined && !("things" in props)) {
+		if (ctx[0] === undefined && !("things" in props)) {
 			console.warn("<Component> was created without expected prop 'things'");
 		}
 
-		if (ctx.foo === undefined && !("foo" in props)) {
+		if (ctx[1] === undefined && !("foo" in props)) {
 			console.warn("<Component> was created without expected prop 'foo'");
 		}
 	}
diff --git a/test/js/samples/debug-hoisted/expected.js b/test/js/samples/debug-hoisted/expected.js
index 7ab1d3348e..57e0d182e4 100644
--- a/test/js/samples/debug-hoisted/expected.js
+++ b/test/js/samples/debug-hoisted/expected.js
@@ -23,7 +23,7 @@ function create_fragment(ctx) {
 		},
 		m: noop,
 		p: function update(changed, ctx) {
-			if (changed.obj || changed.kobzol) {
+			if (changed & 3) {
 				const { obj } = ctx;
 				console.log({ obj, kobzol });
 				debugger;
@@ -45,21 +45,20 @@ function create_fragment(ctx) {
 	return block;
 }
 
-let kobzol = 5;
-
 function instance($$self) {
 	let obj = { x: 5 };
+	let kobzol = 5;
 
 	$$self.$capture_state = () => {
 		return {};
 	};
 
 	$$self.$inject_state = $$props => {
-		if ("obj" in $$props) $$invalidate("obj", obj = $$props.obj);
-		if ("kobzol" in $$props) $$invalidate("kobzol", kobzol = $$props.kobzol);
+		if ("obj" in $$props) $$invalidate(0, obj = $$props.obj);
+		if ("kobzol" in $$props) $$invalidate(1, kobzol = $$props.kobzol);
 	};
 
-	return { obj };
+	return [obj, kobzol];
 }
 
 class Component extends SvelteComponentDev {
diff --git a/test/js/samples/debug-no-dependencies/expected.js b/test/js/samples/debug-no-dependencies/expected.js
index 903bdb83b6..31a81e8c5f 100644
--- a/test/js/samples/debug-no-dependencies/expected.js
+++ b/test/js/samples/debug-no-dependencies/expected.js
@@ -16,16 +16,16 @@ import {
 const file = undefined;
 
 function get_each_context(ctx, list, i) {
-	const child_ctx = Object.create(ctx);
-	child_ctx.thing = list[i];
-	child_ctx.index = i;
+	const child_ctx = ctx.slice();
+	child_ctx[0] = list[i];
+	child_ctx[2] = i;
 	return child_ctx;
 }
 
 // (4:0) {#each things as thing, index}
 function create_each_block(ctx) {
 	let t0;
-	let t1_value = ctx.thing + "";
+	let t1_value = ctx[0] + "";
 	let t1;
 
 	const block = {
@@ -88,8 +88,8 @@ function create_fragment(ctx) {
 
 			insert_dev(target, each_1_anchor, anchor);
 		},
-		p: function update(changed, ctx) {
-			if (changed.things) {
+		p: function update(ctx, changed) {
+			if (changed & 1) {
 				each_value = things;
 				let i;
 
@@ -97,7 +97,7 @@ function create_fragment(ctx) {
 					const child_ctx = get_each_context(ctx, each_value, i);
 
 					if (each_blocks[i]) {
-						each_blocks[i].p(changed, child_ctx);
+						each_blocks[i].p(child_ctx, changed);
 					} else {
 						each_blocks[i] = create_each_block(child_ctx);
 						each_blocks[i].c();
diff --git a/test/js/samples/deconflict-builtins/expected.js b/test/js/samples/deconflict-builtins/expected.js
index 54448a91b4..1f13224b30 100644
--- a/test/js/samples/deconflict-builtins/expected.js
+++ b/test/js/samples/deconflict-builtins/expected.js
@@ -15,15 +15,15 @@ import {
 } from "svelte/internal";
 
 function get_each_context(ctx, list, i) {
-	const child_ctx = Object.create(ctx);
-	child_ctx.node = list[i];
+	const child_ctx = ctx.slice();
+	child_ctx[1] = list[i];
 	return child_ctx;
 }
 
 // (5:0) {#each createElement as node}
 function create_each_block(ctx) {
 	let span;
-	let t_value = ctx.node + "";
+	let t_value = ctx[1] + "";
 	let t;
 
 	return {
@@ -35,8 +35,8 @@ function create_each_block(ctx) {
 			insert(target, span, anchor);
 			append(span, t);
 		},
-		p(changed, ctx) {
-			if (changed.createElement && t_value !== (t_value = ctx.node + "")) set_data(t, t_value);
+		p(ctx, changed) {
+			if (changed & 1 && t_value !== (t_value = ctx[1] + "")) set_data(t, t_value);
 		},
 		d(detaching) {
 			if (detaching) detach(span);
@@ -46,7 +46,7 @@ function create_each_block(ctx) {
 
 function create_fragment(ctx) {
 	let each_1_anchor;
-	let each_value = ctx.createElement;
+	let each_value = ctx[0];
 	let each_blocks = [];
 
 	for (let i = 0; i < each_value.length; i += 1) {
@@ -68,16 +68,16 @@ function create_fragment(ctx) {
 
 			insert(target, each_1_anchor, anchor);
 		},
-		p(changed, ctx) {
-			if (changed.createElement) {
-				each_value = ctx.createElement;
+		p(ctx, changed) {
+			if (changed & 1) {
+				each_value = ctx[0];
 				let i;
 
 				for (i = 0; i < each_value.length; i += 1) {
 					const child_ctx = get_each_context(ctx, each_value, i);
 
 					if (each_blocks[i]) {
-						each_blocks[i].p(changed, child_ctx);
+						each_blocks[i].p(child_ctx, changed);
 					} else {
 						each_blocks[i] = create_each_block(child_ctx);
 						each_blocks[i].c();
@@ -105,10 +105,10 @@ function instance($$self, $$props, $$invalidate) {
 	let { createElement } = $$props;
 
 	$$self.$set = $$props => {
-		if ("createElement" in $$props) $$invalidate("createElement", createElement = $$props.createElement);
+		if ("createElement" in $$props) $$invalidate(0, createElement = $$props.createElement);
 	};
 
-	return { createElement };
+	return [createElement, null, null, null];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/deconflict-globals/expected.js b/test/js/samples/deconflict-globals/expected.js
index 6bd0c596b9..7e83c21f0e 100644
--- a/test/js/samples/deconflict-globals/expected.js
+++ b/test/js/samples/deconflict-globals/expected.js
@@ -11,10 +11,10 @@ function instance($$self, $$props, $$invalidate) {
 	});
 
 	$$self.$set = $$props => {
-		if ("foo" in $$props) $$invalidate("foo", foo = $$props.foo);
+		if ("foo" in $$props) $$invalidate(0, foo = $$props.foo);
 	};
 
-	return { foo };
+	return [foo];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/dev-warning-missing-data-computed/expected.js b/test/js/samples/dev-warning-missing-data-computed/expected.js
index 5da2b4aead..42c0f17a41 100644
--- a/test/js/samples/dev-warning-missing-data-computed/expected.js
+++ b/test/js/samples/dev-warning-missing-data-computed/expected.js
@@ -19,7 +19,7 @@ const file = undefined;
 
 function create_fragment(ctx) {
 	let p;
-	let t0_value = Math.max(0, ctx.foo) + "";
+	let t0_value = Math.max(0, ctx[0]) + "";
 	let t0;
 	let t1;
 	let t2;
@@ -29,7 +29,7 @@ function create_fragment(ctx) {
 			p = element("p");
 			t0 = text(t0_value);
 			t1 = space();
-			t2 = text(ctx.bar);
+			t2 = text(ctx[1]);
 			add_location(p, file, 7, 0, 67);
 		},
 		l: function claim(nodes) {
@@ -41,9 +41,9 @@ function create_fragment(ctx) {
 			append_dev(p, t1);
 			append_dev(p, t2);
 		},
-		p: function update(changed, ctx) {
-			if (changed.foo && t0_value !== (t0_value = Math.max(0, ctx.foo) + "")) set_data_dev(t0, t0_value);
-			if (changed.bar) set_data_dev(t2, ctx.bar);
+		p: function update(ctx, changed) {
+			if (changed & 1 && t0_value !== (t0_value = Math.max(0, ctx[0]) + "")) set_data_dev(t0, t0_value);
+			if (changed & 2) set_data_dev(t2, ctx[1]);
 		},
 		i: noop,
 		o: noop,
@@ -73,7 +73,7 @@ function instance($$self, $$props, $$invalidate) {
 	});
 
 	$$self.$set = $$props => {
-		if ("foo" in $$props) $$invalidate("foo", foo = $$props.foo);
+		if ("foo" in $$props) $$invalidate(0, foo = $$props.foo);
 	};
 
 	$$self.$capture_state = () => {
@@ -81,17 +81,17 @@ function instance($$self, $$props, $$invalidate) {
 	};
 
 	$$self.$inject_state = $$props => {
-		if ("foo" in $$props) $$invalidate("foo", foo = $$props.foo);
-		if ("bar" in $$props) $$invalidate("bar", bar = $$props.bar);
+		if ("foo" in $$props) $$invalidate(0, foo = $$props.foo);
+		if ("bar" in $$props) $$invalidate(1, bar = $$props.bar);
 	};
 
-	$$self.$$.update = (changed = { foo: 1 }) => {
-		if (changed.foo) {
-			$: $$invalidate("bar", bar = foo * 2);
+	$$self.$$.update = () => {
+		if ($$self.$$.dirty & 1) {
+			$: $$invalidate(1, bar = foo * 2);
 		}
 	};
 
-	return { foo, bar };
+	return [foo, bar];
 }
 
 class Component extends SvelteComponentDev {
@@ -109,7 +109,7 @@ class Component extends SvelteComponentDev {
 		const { ctx } = this.$$;
 		const props = options.props || ({});
 
-		if (ctx.foo === undefined && !("foo" in props)) {
+		if (ctx[0] === undefined && !("foo" in props)) {
 			console.warn("<Component> was created without expected prop 'foo'");
 		}
 	}
diff --git a/test/js/samples/each-block-array-literal/expected.js b/test/js/samples/each-block-array-literal/expected.js
index 3804cab6bb..8f6e902c21 100644
--- a/test/js/samples/each-block-array-literal/expected.js
+++ b/test/js/samples/each-block-array-literal/expected.js
@@ -15,15 +15,15 @@ import {
 } from "svelte/internal";
 
 function get_each_context(ctx, list, i) {
-	const child_ctx = Object.create(ctx);
-	child_ctx.num = list[i];
+	const child_ctx = ctx.slice();
+	child_ctx[5] = list[i];
 	return child_ctx;
 }
 
 // (9:0) {#each [a, b, c, d, e] as num}
 function create_each_block(ctx) {
 	let span;
-	let t_value = ctx.num + "";
+	let t_value = ctx[5] + "";
 	let t;
 
 	return {
@@ -35,8 +35,8 @@ function create_each_block(ctx) {
 			insert(target, span, anchor);
 			append(span, t);
 		},
-		p(changed, ctx) {
-			if ((changed.a || changed.b || changed.c || changed.d || changed.e) && t_value !== (t_value = ctx.num + "")) set_data(t, t_value);
+		p(ctx, changed) {
+			if (changed & 31 && t_value !== (t_value = ctx[5] + "")) set_data(t, t_value);
 		},
 		d(detaching) {
 			if (detaching) detach(span);
@@ -46,7 +46,7 @@ function create_each_block(ctx) {
 
 function create_fragment(ctx) {
 	let each_1_anchor;
-	let each_value = [ctx.a, ctx.b, ctx.c, ctx.d, ctx.e];
+	let each_value = [ctx[0], ctx[1], ctx[2], ctx[3], ctx[4]];
 	let each_blocks = [];
 
 	for (let i = 0; i < 5; i += 1) {
@@ -68,16 +68,16 @@ function create_fragment(ctx) {
 
 			insert(target, each_1_anchor, anchor);
 		},
-		p(changed, ctx) {
-			if (changed.a || changed.b || changed.c || changed.d || changed.e) {
-				each_value = [ctx.a, ctx.b, ctx.c, ctx.d, ctx.e];
+		p(ctx, changed) {
+			if (changed & 31) {
+				each_value = [ctx[0], ctx[1], ctx[2], ctx[3], ctx[4]];
 				let i;
 
 				for (i = 0; i < 5; i += 1) {
 					const child_ctx = get_each_context(ctx, each_value, i);
 
 					if (each_blocks[i]) {
-						each_blocks[i].p(changed, child_ctx);
+						each_blocks[i].p(child_ctx, changed);
 					} else {
 						each_blocks[i] = create_each_block(child_ctx);
 						each_blocks[i].c();
@@ -107,20 +107,20 @@ function instance($$self, $$props, $$invalidate) {
 	let { e } = $$props;
 
 	$$self.$set = $$props => {
-		if ("a" in $$props) $$invalidate("a", a = $$props.a);
-		if ("b" in $$props) $$invalidate("b", b = $$props.b);
-		if ("c" in $$props) $$invalidate("c", c = $$props.c);
-		if ("d" in $$props) $$invalidate("d", d = $$props.d);
-		if ("e" in $$props) $$invalidate("e", e = $$props.e);
+		if ("a" in $$props) $$invalidate(0, a = $$props.a);
+		if ("b" in $$props) $$invalidate(1, b = $$props.b);
+		if ("c" in $$props) $$invalidate(2, c = $$props.c);
+		if ("d" in $$props) $$invalidate(3, d = $$props.d);
+		if ("e" in $$props) $$invalidate(4, e = $$props.e);
 	};
 
-	return { a, b, c, d, e };
+	return [a, b, c, d, e, null, null, null];
 }
 
 class Component extends SvelteComponent {
 	constructor(options) {
 		super();
-		init(this, options, instance, create_fragment, safe_not_equal, { a: 0, b: 0, c: 0, d: 0, e: 0 });
+		init(this, options, instance, create_fragment, safe_not_equal, { a: 0, b: 1, c: 2, d: 3, e: 4 });
 	}
 }
 
diff --git a/test/js/samples/each-block-changed-check/expected.js b/test/js/samples/each-block-changed-check/expected.js
index a2735ae9c4..56c399cdc5 100644
--- a/test/js/samples/each-block-changed-check/expected.js
+++ b/test/js/samples/each-block-changed-check/expected.js
@@ -17,9 +17,9 @@ import {
 } from "svelte/internal";
 
 function get_each_context(ctx, list, i) {
-	const child_ctx = Object.create(ctx);
-	child_ctx.comment = list[i];
-	child_ctx.i = i;
+	const child_ctx = ctx.slice();
+	child_ctx[4] = list[i];
+	child_ctx[6] = i;
 	return child_ctx;
 }
 
@@ -30,21 +30,21 @@ function create_each_block(ctx) {
 	let t0;
 	let t1;
 	let span;
-	let t2_value = ctx.comment.author + "";
+	let t2_value = ctx[4].author + "";
 	let t2;
 	let t3;
-	let t4_value = ctx.elapsed(ctx.comment.time, ctx.time) + "";
+	let t4_value = ctx[1](ctx[4].time, ctx[2]) + "";
 	let t4;
 	let t5;
 	let t6;
 	let html_tag;
-	let raw_value = ctx.comment.html + "";
+	let raw_value = ctx[4].html + "";
 
 	return {
 		c() {
 			div = element("div");
 			strong = element("strong");
-			t0 = text(ctx.i);
+			t0 = text(ctx[6]);
 			t1 = space();
 			span = element("span");
 			t2 = text(t2_value);
@@ -69,10 +69,10 @@ function create_each_block(ctx) {
 			append(div, t6);
 			html_tag.m(div);
 		},
-		p(changed, ctx) {
-			if (changed.comments && t2_value !== (t2_value = ctx.comment.author + "")) set_data(t2, t2_value);
-			if ((changed.elapsed || changed.comments || changed.time) && t4_value !== (t4_value = ctx.elapsed(ctx.comment.time, ctx.time) + "")) set_data(t4, t4_value);
-			if (changed.comments && raw_value !== (raw_value = ctx.comment.html + "")) html_tag.p(raw_value);
+		p(ctx, changed) {
+			if (changed & 1 && t2_value !== (t2_value = ctx[4].author + "")) set_data(t2, t2_value);
+			if (changed & 7 && t4_value !== (t4_value = ctx[1](ctx[4].time, ctx[2]) + "")) set_data(t4, t4_value);
+			if (changed & 1 && raw_value !== (raw_value = ctx[4].html + "")) html_tag.p(raw_value);
 		},
 		d(detaching) {
 			if (detaching) detach(div);
@@ -84,7 +84,7 @@ function create_fragment(ctx) {
 	let t0;
 	let p;
 	let t1;
-	let each_value = ctx.comments;
+	let each_value = ctx[0];
 	let each_blocks = [];
 
 	for (let i = 0; i < each_value.length; i += 1) {
@@ -99,7 +99,7 @@ function create_fragment(ctx) {
 
 			t0 = space();
 			p = element("p");
-			t1 = text(ctx.foo);
+			t1 = text(ctx[3]);
 		},
 		m(target, anchor) {
 			for (let i = 0; i < each_blocks.length; i += 1) {
@@ -110,16 +110,16 @@ function create_fragment(ctx) {
 			insert(target, p, anchor);
 			append(p, t1);
 		},
-		p(changed, ctx) {
-			if (changed.comments || changed.elapsed || changed.time) {
-				each_value = ctx.comments;
+		p(ctx, changed) {
+			if (changed & 7) {
+				each_value = ctx[0];
 				let i;
 
 				for (i = 0; i < each_value.length; i += 1) {
 					const child_ctx = get_each_context(ctx, each_value, i);
 
 					if (each_blocks[i]) {
-						each_blocks[i].p(changed, child_ctx);
+						each_blocks[i].p(child_ctx, changed);
 					} else {
 						each_blocks[i] = create_each_block(child_ctx);
 						each_blocks[i].c();
@@ -134,7 +134,7 @@ function create_fragment(ctx) {
 				each_blocks.length = each_value.length;
 			}
 
-			if (changed.foo) set_data(t1, ctx.foo);
+			if (changed & 8) set_data(t1, ctx[3]);
 		},
 		i: noop,
 		o: noop,
@@ -153,19 +153,19 @@ function instance($$self, $$props, $$invalidate) {
 	let { foo } = $$props;
 
 	$$self.$set = $$props => {
-		if ("comments" in $$props) $$invalidate("comments", comments = $$props.comments);
-		if ("elapsed" in $$props) $$invalidate("elapsed", elapsed = $$props.elapsed);
-		if ("time" in $$props) $$invalidate("time", time = $$props.time);
-		if ("foo" in $$props) $$invalidate("foo", foo = $$props.foo);
+		if ("comments" in $$props) $$invalidate(0, comments = $$props.comments);
+		if ("elapsed" in $$props) $$invalidate(1, elapsed = $$props.elapsed);
+		if ("time" in $$props) $$invalidate(2, time = $$props.time);
+		if ("foo" in $$props) $$invalidate(3, foo = $$props.foo);
 	};
 
-	return { comments, elapsed, time, foo };
+	return [comments, elapsed, time, foo, null, null, null];
 }
 
 class Component extends SvelteComponent {
 	constructor(options) {
 		super();
-		init(this, options, instance, create_fragment, safe_not_equal, { comments: 0, elapsed: 0, time: 0, foo: 0 });
+		init(this, options, instance, create_fragment, safe_not_equal, { comments: 0, elapsed: 1, time: 2, foo: 3 });
 	}
 }
 
diff --git a/test/js/samples/each-block-keyed-animated/expected.js b/test/js/samples/each-block-keyed-animated/expected.js
index e3661764b1..780f5c6db2 100644
--- a/test/js/samples/each-block-keyed-animated/expected.js
+++ b/test/js/samples/each-block-keyed-animated/expected.js
@@ -18,15 +18,15 @@ import {
 } from "svelte/internal";
 
 function get_each_context(ctx, list, i) {
-	const child_ctx = Object.create(ctx);
-	child_ctx.thing = list[i];
+	const child_ctx = ctx.slice();
+	child_ctx[1] = list[i];
 	return child_ctx;
 }
 
 // (19:0) {#each things as thing (thing.id)}
 function create_each_block(key_1, ctx) {
 	let div;
-	let t_value = ctx.thing.name + "";
+	let t_value = ctx[1].name + "";
 	let t;
 	let rect;
 	let stop_animation = noop;
@@ -43,8 +43,8 @@ function create_each_block(key_1, ctx) {
 			insert(target, div, anchor);
 			append(div, t);
 		},
-		p(changed, ctx) {
-			if (changed.things && t_value !== (t_value = ctx.thing.name + "")) set_data(t, t_value);
+		p(ctx, changed) {
+			if (changed & 1 && t_value !== (t_value = ctx[1].name + "")) set_data(t, t_value);
 		},
 		r() {
 			rect = div.getBoundingClientRect();
@@ -67,8 +67,8 @@ function create_fragment(ctx) {
 	let each_blocks = [];
 	let each_1_lookup = new Map();
 	let each_1_anchor;
-	let each_value = ctx.things;
-	const get_key = ctx => ctx.thing.id;
+	let each_value = ctx[0];
+	const get_key = ctx => ctx[1].id;
 
 	for (let i = 0; i < each_value.length; i += 1) {
 		let child_ctx = get_each_context(ctx, each_value, i);
@@ -91,8 +91,8 @@ function create_fragment(ctx) {
 
 			insert(target, each_1_anchor, anchor);
 		},
-		p(changed, ctx) {
-			const each_value = ctx.things;
+		p(ctx, changed) {
+			const each_value = ctx[0];
 			for (let i = 0; i < each_blocks.length; i += 1) each_blocks[i].r();
 			each_blocks = update_keyed_each(each_blocks, changed, get_key, 1, ctx, each_value, each_1_lookup, each_1_anchor.parentNode, fix_and_destroy_block, create_each_block, each_1_anchor, get_each_context);
 			for (let i = 0; i < each_blocks.length; i += 1) each_blocks[i].a();
@@ -127,10 +127,10 @@ function instance($$self, $$props, $$invalidate) {
 	let { things } = $$props;
 
 	$$self.$set = $$props => {
-		if ("things" in $$props) $$invalidate("things", things = $$props.things);
+		if ("things" in $$props) $$invalidate(0, things = $$props.things);
 	};
 
-	return { things };
+	return [things, null, null, null];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/each-block-keyed/expected.js b/test/js/samples/each-block-keyed/expected.js
index beb5a613bc..dd72e418c7 100644
--- a/test/js/samples/each-block-keyed/expected.js
+++ b/test/js/samples/each-block-keyed/expected.js
@@ -16,15 +16,15 @@ import {
 } from "svelte/internal";
 
 function get_each_context(ctx, list, i) {
-	const child_ctx = Object.create(ctx);
-	child_ctx.thing = list[i];
+	const child_ctx = ctx.slice();
+	child_ctx[1] = list[i];
 	return child_ctx;
 }
 
 // (5:0) {#each things as thing (thing.id)}
 function create_each_block(key_1, ctx) {
 	let div;
-	let t_value = ctx.thing.name + "";
+	let t_value = ctx[1].name + "";
 	let t;
 
 	return {
@@ -39,8 +39,8 @@ function create_each_block(key_1, ctx) {
 			insert(target, div, anchor);
 			append(div, t);
 		},
-		p(changed, ctx) {
-			if (changed.things && t_value !== (t_value = ctx.thing.name + "")) set_data(t, t_value);
+		p(ctx, changed) {
+			if (changed & 1 && t_value !== (t_value = ctx[1].name + "")) set_data(t, t_value);
 		},
 		d(detaching) {
 			if (detaching) detach(div);
@@ -52,8 +52,8 @@ function create_fragment(ctx) {
 	let each_blocks = [];
 	let each_1_lookup = new Map();
 	let each_1_anchor;
-	let each_value = ctx.things;
-	const get_key = ctx => ctx.thing.id;
+	let each_value = ctx[0];
+	const get_key = ctx => ctx[1].id;
 
 	for (let i = 0; i < each_value.length; i += 1) {
 		let child_ctx = get_each_context(ctx, each_value, i);
@@ -76,8 +76,8 @@ function create_fragment(ctx) {
 
 			insert(target, each_1_anchor, anchor);
 		},
-		p(changed, ctx) {
-			const each_value = ctx.things;
+		p(ctx, changed) {
+			const each_value = ctx[0];
 			each_blocks = update_keyed_each(each_blocks, changed, get_key, 1, ctx, each_value, each_1_lookup, each_1_anchor.parentNode, destroy_block, create_each_block, each_1_anchor, get_each_context);
 		},
 		i: noop,
@@ -96,10 +96,10 @@ function instance($$self, $$props, $$invalidate) {
 	let { things } = $$props;
 
 	$$self.$set = $$props => {
-		if ("things" in $$props) $$invalidate("things", things = $$props.things);
+		if ("things" in $$props) $$invalidate(0, things = $$props.things);
 	};
 
-	return { things };
+	return [things, null, null, null];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/empty-dom/expected.js b/test/js/samples/empty-dom/expected.js
index bd5a9fb7ef..d5c80be696 100644
--- a/test/js/samples/empty-dom/expected.js
+++ b/test/js/samples/empty-dom/expected.js
@@ -3,7 +3,7 @@ import { SvelteComponent, init, safe_not_equal } from "svelte/internal";
 
 function instance($$self) {
 	const a = 1 + 2;
-	return {};
+	return [];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/event-handler-dynamic/expected.js b/test/js/samples/event-handler-dynamic/expected.js
index 515d7e36a9..7778616247 100644
--- a/test/js/samples/event-handler-dynamic/expected.js
+++ b/test/js/samples/event-handler-dynamic/expected.js
@@ -37,16 +37,16 @@ function create_fragment(ctx) {
 			button1.textContent = "set handler 2";
 			t3 = space();
 			p1 = element("p");
-			t4 = text(ctx.number);
+			t4 = text(ctx[1]);
 			t5 = space();
 			button2 = element("button");
 			button2.textContent = "click";
 
 			dispose = [
-				listen(button0, "click", ctx.updateHandler1),
-				listen(button1, "click", ctx.updateHandler2),
+				listen(button0, "click", ctx[2]),
+				listen(button1, "click", ctx[3]),
 				listen(button2, "click", function () {
-					ctx.clickHandler.apply(this, arguments);
+					ctx[0].apply(this, arguments);
 				})
 			];
 		},
@@ -61,9 +61,9 @@ function create_fragment(ctx) {
 			insert(target, t5, anchor);
 			insert(target, button2, anchor);
 		},
-		p(changed, new_ctx) {
+		p(new_ctx, changed) {
 			ctx = new_ctx;
-			if (changed.number) set_data(t4, ctx.number);
+			if (changed & 2) set_data(t4, ctx[1]);
 		},
 		i: noop,
 		o: noop,
@@ -83,19 +83,14 @@ function instance($$self, $$props, $$invalidate) {
 	let number = 0;
 
 	function updateHandler1() {
-		$$invalidate("clickHandler", clickHandler = () => $$invalidate("number", number = 1));
+		$$invalidate(0, clickHandler = () => $$invalidate(1, number = 1));
 	}
 
 	function updateHandler2() {
-		$$invalidate("clickHandler", clickHandler = () => $$invalidate("number", number = 2));
+		$$invalidate(0, clickHandler = () => $$invalidate(1, number = 2));
 	}
 
-	return {
-		clickHandler,
-		number,
-		updateHandler1,
-		updateHandler2
-	};
+	return [clickHandler, number, updateHandler1, updateHandler2];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/if-block-complex/expected.js b/test/js/samples/if-block-complex/expected.js
index badae4a2c0..a40e0e8afb 100644
--- a/test/js/samples/if-block-complex/expected.js
+++ b/test/js/samples/if-block-complex/expected.js
@@ -29,7 +29,7 @@ function create_if_block(ctx) {
 }
 
 function create_fragment(ctx) {
-	let show_if = ctx.item.divider && ctx.item.divider.includes(1);
+	let show_if = ctx[0].divider && ctx[0].divider.includes(1);
 	let if_block_anchor;
 	let if_block = show_if && create_if_block(ctx);
 
@@ -54,7 +54,7 @@ function create_fragment(ctx) {
 
 function instance($$self) {
 	let item = { divider: [1] };
-	return { item };
+	return [item];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/if-block-no-update/expected.js b/test/js/samples/if-block-no-update/expected.js
index b057041e88..a7982a1f7d 100644
--- a/test/js/samples/if-block-no-update/expected.js
+++ b/test/js/samples/if-block-no-update/expected.js
@@ -48,12 +48,12 @@ function create_if_block(ctx) {
 function create_fragment(ctx) {
 	let if_block_anchor;
 
-	function select_block_type(changed, ctx) {
-		if (ctx.foo) return create_if_block;
+	function select_block_type(ctx, changed) {
+		if (ctx[0]) return create_if_block;
 		return create_else_block;
 	}
 
-	let current_block_type = select_block_type(null, ctx);
+	let current_block_type = select_block_type(ctx, -1);
 	let if_block = current_block_type(ctx);
 
 	return {
@@ -65,8 +65,8 @@ function create_fragment(ctx) {
 			if_block.m(target, anchor);
 			insert(target, if_block_anchor, anchor);
 		},
-		p(changed, ctx) {
-			if (current_block_type !== (current_block_type = select_block_type(changed, ctx))) {
+		p(ctx, changed) {
+			if (current_block_type !== (current_block_type = select_block_type(ctx, changed))) {
 				if_block.d(1);
 				if_block = current_block_type(ctx);
 
@@ -89,10 +89,10 @@ function instance($$self, $$props, $$invalidate) {
 	let { foo } = $$props;
 
 	$$self.$set = $$props => {
-		if ("foo" in $$props) $$invalidate("foo", foo = $$props.foo);
+		if ("foo" in $$props) $$invalidate(0, foo = $$props.foo);
 	};
 
-	return { foo };
+	return [foo];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/if-block-simple/expected.js b/test/js/samples/if-block-simple/expected.js
index fd2185b86d..af311c43fe 100644
--- a/test/js/samples/if-block-simple/expected.js
+++ b/test/js/samples/if-block-simple/expected.js
@@ -29,7 +29,7 @@ function create_if_block(ctx) {
 
 function create_fragment(ctx) {
 	let if_block_anchor;
-	let if_block = ctx.foo && create_if_block(ctx);
+	let if_block = ctx[0] && create_if_block(ctx);
 
 	return {
 		c() {
@@ -40,14 +40,14 @@ function create_fragment(ctx) {
 			if (if_block) if_block.m(target, anchor);
 			insert(target, if_block_anchor, anchor);
 		},
-		p(changed, ctx) {
-			if (ctx.foo) {
+		p(ctx, changed) {
+			if (ctx[0]) {
 				if (!if_block) {
 					if_block = create_if_block(ctx);
 					if_block.c();
 					if_block.m(if_block_anchor.parentNode, if_block_anchor);
 				} else {
-					
+
 				}
 			} else if (if_block) {
 				if_block.d(1);
@@ -67,10 +67,10 @@ function instance($$self, $$props, $$invalidate) {
 	let { foo } = $$props;
 
 	$$self.$set = $$props => {
-		if ("foo" in $$props) $$invalidate("foo", foo = $$props.foo);
+		if ("foo" in $$props) $$invalidate(0, foo = $$props.foo);
 	};
 
-	return { foo };
+	return [foo];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/inline-style-optimized-multiple/expected.js b/test/js/samples/inline-style-optimized-multiple/expected.js
index 636a4f19bb..efb3637297 100644
--- a/test/js/samples/inline-style-optimized-multiple/expected.js
+++ b/test/js/samples/inline-style-optimized-multiple/expected.js
@@ -16,19 +16,19 @@ function create_fragment(ctx) {
 	return {
 		c() {
 			div = element("div");
-			set_style(div, "color", ctx.color);
-			set_style(div, "transform", "translate(" + ctx.x + "px," + ctx.y + "px)");
+			set_style(div, "color", ctx[0]);
+			set_style(div, "transform", "translate(" + ctx[1] + "px," + ctx[2] + "px)");
 		},
 		m(target, anchor) {
 			insert(target, div, anchor);
 		},
-		p(changed, ctx) {
-			if (changed.color) {
-				set_style(div, "color", ctx.color);
+		p(ctx, changed) {
+			if (changed & 1) {
+				set_style(div, "color", ctx[0]);
 			}
 
-			if (changed.x || changed.y) {
-				set_style(div, "transform", "translate(" + ctx.x + "px," + ctx.y + "px)");
+			if (changed & 6) {
+				set_style(div, "transform", "translate(" + ctx[1] + "px," + ctx[2] + "px)");
 			}
 		},
 		i: noop,
@@ -45,18 +45,18 @@ function instance($$self, $$props, $$invalidate) {
 	let { y } = $$props;
 
 	$$self.$set = $$props => {
-		if ("color" in $$props) $$invalidate("color", color = $$props.color);
-		if ("x" in $$props) $$invalidate("x", x = $$props.x);
-		if ("y" in $$props) $$invalidate("y", y = $$props.y);
+		if ("color" in $$props) $$invalidate(0, color = $$props.color);
+		if ("x" in $$props) $$invalidate(1, x = $$props.x);
+		if ("y" in $$props) $$invalidate(2, y = $$props.y);
 	};
 
-	return { color, x, y };
+	return [color, x, y];
 }
 
 class Component extends SvelteComponent {
 	constructor(options) {
 		super();
-		init(this, options, instance, create_fragment, safe_not_equal, { color: 0, x: 0, y: 0 });
+		init(this, options, instance, create_fragment, safe_not_equal, { color: 0, x: 1, y: 2 });
 	}
 }
 
diff --git a/test/js/samples/inline-style-optimized-url/expected.js b/test/js/samples/inline-style-optimized-url/expected.js
index 53a9434369..9d11d96055 100644
--- a/test/js/samples/inline-style-optimized-url/expected.js
+++ b/test/js/samples/inline-style-optimized-url/expected.js
@@ -16,14 +16,14 @@ function create_fragment(ctx) {
 	return {
 		c() {
 			div = element("div");
-			set_style(div, "background", "url(data:image/png;base64," + ctx.data + ")");
+			set_style(div, "background", "url(data:image/png;base64," + ctx[0] + ")");
 		},
 		m(target, anchor) {
 			insert(target, div, anchor);
 		},
-		p(changed, ctx) {
-			if (changed.data) {
-				set_style(div, "background", "url(data:image/png;base64," + ctx.data + ")");
+		p(ctx, changed) {
+			if (changed & 1) {
+				set_style(div, "background", "url(data:image/png;base64," + ctx[0] + ")");
 			}
 		},
 		i: noop,
@@ -38,10 +38,10 @@ function instance($$self, $$props, $$invalidate) {
 	let { data } = $$props;
 
 	$$self.$set = $$props => {
-		if ("data" in $$props) $$invalidate("data", data = $$props.data);
+		if ("data" in $$props) $$invalidate(0, data = $$props.data);
 	};
 
-	return { data };
+	return [data];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/inline-style-optimized/expected.js b/test/js/samples/inline-style-optimized/expected.js
index 95079a63fe..f9def765d1 100644
--- a/test/js/samples/inline-style-optimized/expected.js
+++ b/test/js/samples/inline-style-optimized/expected.js
@@ -16,14 +16,14 @@ function create_fragment(ctx) {
 	return {
 		c() {
 			div = element("div");
-			set_style(div, "color", ctx.color);
+			set_style(div, "color", ctx[0]);
 		},
 		m(target, anchor) {
 			insert(target, div, anchor);
 		},
-		p(changed, ctx) {
-			if (changed.color) {
-				set_style(div, "color", ctx.color);
+		p(ctx, changed) {
+			if (changed & 1) {
+				set_style(div, "color", ctx[0]);
 			}
 		},
 		i: noop,
@@ -38,10 +38,10 @@ function instance($$self, $$props, $$invalidate) {
 	let { color } = $$props;
 
 	$$self.$set = $$props => {
-		if ("color" in $$props) $$invalidate("color", color = $$props.color);
+		if ("color" in $$props) $$invalidate(0, color = $$props.color);
 	};
 
-	return { color };
+	return [color];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/inline-style-unoptimized/expected.js b/test/js/samples/inline-style-unoptimized/expected.js
index 11eaddbdf7..a40e0e7e73 100644
--- a/test/js/samples/inline-style-unoptimized/expected.js
+++ b/test/js/samples/inline-style-unoptimized/expected.js
@@ -22,20 +22,20 @@ function create_fragment(ctx) {
 			div0 = element("div");
 			t = space();
 			div1 = element("div");
-			attr(div0, "style", ctx.style);
-			attr(div1, "style", div1_style_value = "" + (ctx.key + ": " + ctx.value));
+			attr(div0, "style", ctx[0]);
+			attr(div1, "style", div1_style_value = "" + (ctx[1] + ": " + ctx[2]));
 		},
 		m(target, anchor) {
 			insert(target, div0, anchor);
 			insert(target, t, anchor);
 			insert(target, div1, anchor);
 		},
-		p(changed, ctx) {
-			if (changed.style) {
-				attr(div0, "style", ctx.style);
+		p(ctx, changed) {
+			if (changed & 1) {
+				attr(div0, "style", ctx[0]);
 			}
 
-			if ((changed.key || changed.value) && div1_style_value !== (div1_style_value = "" + (ctx.key + ": " + ctx.value))) {
+			if (changed & 6 && div1_style_value !== (div1_style_value = "" + (ctx[1] + ": " + ctx[2]))) {
 				attr(div1, "style", div1_style_value);
 			}
 		},
@@ -55,18 +55,18 @@ function instance($$self, $$props, $$invalidate) {
 	let { value } = $$props;
 
 	$$self.$set = $$props => {
-		if ("style" in $$props) $$invalidate("style", style = $$props.style);
-		if ("key" in $$props) $$invalidate("key", key = $$props.key);
-		if ("value" in $$props) $$invalidate("value", value = $$props.value);
+		if ("style" in $$props) $$invalidate(0, style = $$props.style);
+		if ("key" in $$props) $$invalidate(1, key = $$props.key);
+		if ("value" in $$props) $$invalidate(2, value = $$props.value);
 	};
 
-	return { style, key, value };
+	return [style, key, value];
 }
 
 class Component extends SvelteComponent {
 	constructor(options) {
 		super();
-		init(this, options, instance, create_fragment, safe_not_equal, { style: 0, key: 0, value: 0 });
+		init(this, options, instance, create_fragment, safe_not_equal, { style: 0, key: 1, value: 2 });
 	}
 }
 
diff --git a/test/js/samples/input-files/expected.js b/test/js/samples/input-files/expected.js
index a190d6cf72..08745fa730 100644
--- a/test/js/samples/input-files/expected.js
+++ b/test/js/samples/input-files/expected.js
@@ -20,7 +20,7 @@ function create_fragment(ctx) {
 			input = element("input");
 			attr(input, "type", "file");
 			input.multiple = true;
-			dispose = listen(input, "change", ctx.input_change_handler);
+			dispose = listen(input, "change", ctx[1]);
 		},
 		m(target, anchor) {
 			insert(target, input, anchor);
@@ -40,14 +40,14 @@ function instance($$self, $$props, $$invalidate) {
 
 	function input_change_handler() {
 		files = this.files;
-		$$invalidate("files", files);
+		$$invalidate(0, files);
 	}
 
 	$$self.$set = $$props => {
-		if ("files" in $$props) $$invalidate("files", files = $$props.files);
+		if ("files" in $$props) $$invalidate(0, files = $$props.files);
 	};
 
-	return { files, input_change_handler };
+	return [files, input_change_handler];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/input-no-initial-value/expected.js b/test/js/samples/input-no-initial-value/expected.js
index 85bc9dfcef..15f87b1d81 100644
--- a/test/js/samples/input-no-initial-value/expected.js
+++ b/test/js/samples/input-no-initial-value/expected.js
@@ -31,22 +31,18 @@ function create_fragment(ctx) {
 			button.textContent = "Store";
 			attr(input, "type", "text");
 			input.required = true;
-
-			dispose = [
-				listen(input, "input", ctx.input_input_handler),
-				listen(form, "submit", ctx.handleSubmit)
-			];
+			dispose = [listen(input, "input", ctx[2]), listen(form, "submit", ctx[1])];
 		},
 		m(target, anchor) {
 			insert(target, form, anchor);
 			append(form, input);
-			set_input_value(input, ctx.test);
+			set_input_value(input, ctx[0]);
 			append(form, t0);
 			append(form, button);
 		},
-		p(changed, ctx) {
-			if (changed.test && input.value !== ctx.test) {
-				set_input_value(input, ctx.test);
+		p(ctx, changed) {
+			if (changed & 1 && input.value !== ctx[0]) {
+				set_input_value(input, ctx[0]);
 			}
 		},
 		i: noop,
@@ -68,10 +64,10 @@ function instance($$self, $$props, $$invalidate) {
 
 	function input_input_handler() {
 		test = this.value;
-		$$invalidate("test", test);
+		$$invalidate(0, test);
 	}
 
-	return { test, handleSubmit, input_input_handler };
+	return [test, handleSubmit, input_input_handler];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/input-range/expected.js b/test/js/samples/input-range/expected.js
index 2ea13df038..ecf36ab2f6 100644
--- a/test/js/samples/input-range/expected.js
+++ b/test/js/samples/input-range/expected.js
@@ -22,19 +22,15 @@ function create_fragment(ctx) {
 		c() {
 			input = element("input");
 			attr(input, "type", "range");
-
-			dispose = [
-				listen(input, "change", ctx.input_change_input_handler),
-				listen(input, "input", ctx.input_change_input_handler)
-			];
+			dispose = [listen(input, "change", ctx[1]), listen(input, "input", ctx[1])];
 		},
 		m(target, anchor) {
 			insert(target, input, anchor);
-			set_input_value(input, ctx.value);
+			set_input_value(input, ctx[0]);
 		},
-		p(changed, ctx) {
-			if (changed.value) {
-				set_input_value(input, ctx.value);
+		p(ctx, changed) {
+			if (changed & 1) {
+				set_input_value(input, ctx[0]);
 			}
 		},
 		i: noop,
@@ -51,14 +47,14 @@ function instance($$self, $$props, $$invalidate) {
 
 	function input_change_input_handler() {
 		value = to_number(this.value);
-		$$invalidate("value", value);
+		$$invalidate(0, value);
 	}
 
 	$$self.$set = $$props => {
-		if ("value" in $$props) $$invalidate("value", value = $$props.value);
+		if ("value" in $$props) $$invalidate(0, value = $$props.value);
 	};
 
-	return { value, input_change_input_handler };
+	return [value, input_change_input_handler];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/input-without-blowback-guard/expected.js b/test/js/samples/input-without-blowback-guard/expected.js
index eacdbece83..aa52f72040 100644
--- a/test/js/samples/input-without-blowback-guard/expected.js
+++ b/test/js/samples/input-without-blowback-guard/expected.js
@@ -19,15 +19,15 @@ function create_fragment(ctx) {
 		c() {
 			input = element("input");
 			attr(input, "type", "checkbox");
-			dispose = listen(input, "change", ctx.input_change_handler);
+			dispose = listen(input, "change", ctx[1]);
 		},
 		m(target, anchor) {
 			insert(target, input, anchor);
-			input.checked = ctx.foo;
+			input.checked = ctx[0];
 		},
-		p(changed, ctx) {
-			if (changed.foo) {
-				input.checked = ctx.foo;
+		p(ctx, changed) {
+			if (changed & 1) {
+				input.checked = ctx[0];
 			}
 		},
 		i: noop,
@@ -44,14 +44,14 @@ function instance($$self, $$props, $$invalidate) {
 
 	function input_change_handler() {
 		foo = this.checked;
-		$$invalidate("foo", foo);
+		$$invalidate(0, foo);
 	}
 
 	$$self.$set = $$props => {
-		if ("foo" in $$props) $$invalidate("foo", foo = $$props.foo);
+		if ("foo" in $$props) $$invalidate(0, foo = $$props.foo);
 	};
 
-	return { foo, input_change_handler };
+	return [foo, input_change_handler];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/instrumentation-script-if-no-block/expected.js b/test/js/samples/instrumentation-script-if-no-block/expected.js
index 4b0574b79d..70c5e25e8d 100644
--- a/test/js/samples/instrumentation-script-if-no-block/expected.js
+++ b/test/js/samples/instrumentation-script-if-no-block/expected.js
@@ -29,8 +29,8 @@ function create_fragment(ctx) {
 			t1 = space();
 			p = element("p");
 			t2 = text("x: ");
-			t3 = text(ctx.x);
-			dispose = listen(button, "click", ctx.foo);
+			t3 = text(ctx[0]);
+			dispose = listen(button, "click", ctx[1]);
 		},
 		m(target, anchor) {
 			insert(target, button, anchor);
@@ -39,8 +39,8 @@ function create_fragment(ctx) {
 			append(p, t2);
 			append(p, t3);
 		},
-		p(changed, ctx) {
-			if (changed.x) set_data(t3, ctx.x);
+		p(ctx, changed) {
+			if (changed & 1) set_data(t3, ctx[0]);
 		},
 		i: noop,
 		o: noop,
@@ -57,10 +57,10 @@ function instance($$self, $$props, $$invalidate) {
 	let x = 0;
 
 	function foo() {
-		if (true) $$invalidate("x", x += 1);
+		if (true) $$invalidate(0, x += 1);
 	}
 
-	return { x, foo };
+	return [x, foo];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/instrumentation-script-x-equals-x/expected.js b/test/js/samples/instrumentation-script-x-equals-x/expected.js
index 8a3fa9366a..9b25a9c444 100644
--- a/test/js/samples/instrumentation-script-x-equals-x/expected.js
+++ b/test/js/samples/instrumentation-script-x-equals-x/expected.js
@@ -19,7 +19,7 @@ function create_fragment(ctx) {
 	let t1;
 	let p;
 	let t2;
-	let t3_value = ctx.things.length + "";
+	let t3_value = ctx[0].length + "";
 	let t3;
 	let dispose;
 
@@ -31,7 +31,7 @@ function create_fragment(ctx) {
 			p = element("p");
 			t2 = text("number of things: ");
 			t3 = text(t3_value);
-			dispose = listen(button, "click", ctx.foo);
+			dispose = listen(button, "click", ctx[1]);
 		},
 		m(target, anchor) {
 			insert(target, button, anchor);
@@ -40,8 +40,8 @@ function create_fragment(ctx) {
 			append(p, t2);
 			append(p, t3);
 		},
-		p(changed, ctx) {
-			if (changed.things && t3_value !== (t3_value = ctx.things.length + "")) set_data(t3, t3_value);
+		p(ctx, changed) {
+			if (changed & 1 && t3_value !== (t3_value = ctx[0].length + "")) set_data(t3, t3_value);
 		},
 		i: noop,
 		o: noop,
@@ -59,10 +59,10 @@ function instance($$self, $$props, $$invalidate) {
 
 	function foo() {
 		things.push(1);
-		$$invalidate("things", things);
+		$$invalidate(0, things);
 	}
 
-	return { things, foo };
+	return [things, foo];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/instrumentation-template-if-no-block/expected.js b/test/js/samples/instrumentation-template-if-no-block/expected.js
index e2d8c4466f..18dc615adf 100644
--- a/test/js/samples/instrumentation-template-if-no-block/expected.js
+++ b/test/js/samples/instrumentation-template-if-no-block/expected.js
@@ -29,8 +29,8 @@ function create_fragment(ctx) {
 			t1 = space();
 			p = element("p");
 			t2 = text("x: ");
-			t3 = text(ctx.x);
-			dispose = listen(button, "click", ctx.click_handler);
+			t3 = text(ctx[0]);
+			dispose = listen(button, "click", ctx[1]);
 		},
 		m(target, anchor) {
 			insert(target, button, anchor);
@@ -39,8 +39,8 @@ function create_fragment(ctx) {
 			append(p, t2);
 			append(p, t3);
 		},
-		p(changed, ctx) {
-			if (changed.x) set_data(t3, ctx.x);
+		p(ctx, changed) {
+			if (changed & 1) set_data(t3, ctx[0]);
 		},
 		i: noop,
 		o: noop,
@@ -57,10 +57,10 @@ function instance($$self, $$props, $$invalidate) {
 	let x = 0;
 
 	const click_handler = () => {
-		if (true) $$invalidate("x", x += 1);
+		if (true) $$invalidate(0, x += 1);
 	};
 
-	return { x, click_handler };
+	return [x, click_handler];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/instrumentation-template-x-equals-x/expected.js b/test/js/samples/instrumentation-template-x-equals-x/expected.js
index eefda55f31..0b71f86a5b 100644
--- a/test/js/samples/instrumentation-template-x-equals-x/expected.js
+++ b/test/js/samples/instrumentation-template-x-equals-x/expected.js
@@ -19,7 +19,7 @@ function create_fragment(ctx) {
 	let t1;
 	let p;
 	let t2;
-	let t3_value = ctx.things.length + "";
+	let t3_value = ctx[0].length + "";
 	let t3;
 	let dispose;
 
@@ -31,7 +31,7 @@ function create_fragment(ctx) {
 			p = element("p");
 			t2 = text("number of things: ");
 			t3 = text(t3_value);
-			dispose = listen(button, "click", ctx.click_handler);
+			dispose = listen(button, "click", ctx[1]);
 		},
 		m(target, anchor) {
 			insert(target, button, anchor);
@@ -40,8 +40,8 @@ function create_fragment(ctx) {
 			append(p, t2);
 			append(p, t3);
 		},
-		p(changed, ctx) {
-			if (changed.things && t3_value !== (t3_value = ctx.things.length + "")) set_data(t3, t3_value);
+		p(ctx, changed) {
+			if (changed & 1 && t3_value !== (t3_value = ctx[0].length + "")) set_data(t3, t3_value);
 		},
 		i: noop,
 		o: noop,
@@ -59,10 +59,10 @@ function instance($$self, $$props, $$invalidate) {
 
 	const click_handler = () => {
 		things.push(1);
-		$$invalidate("things", things);
+		$$invalidate(0, things);
 	};
 
-	return { things, click_handler };
+	return [things, click_handler];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/loop-protect/expected.js b/test/js/samples/loop-protect/expected.js
index 59d9a7e43b..e2df5820e1 100644
--- a/test/js/samples/loop-protect/expected.js
+++ b/test/js/samples/loop-protect/expected.js
@@ -68,7 +68,7 @@ function instance($$self) {
 	};
 
 	$$self.$inject_state = $$props => {
-		
+
 	};
 
 	$: {
@@ -89,7 +89,7 @@ function instance($$self) {
 		} while (true);
 	}
 
-	return {};
+	return [];
 }
 
 class Component extends SvelteComponentDev {
diff --git a/test/js/samples/media-bindings/expected.js b/test/js/samples/media-bindings/expected.js
index 0538f07055..0ebd19b4da 100644
--- a/test/js/samples/media-bindings/expected.js
+++ b/test/js/samples/media-bindings/expected.js
@@ -29,59 +29,59 @@ function create_fragment(ctx) {
 			audio_updating = true;
 		}
 
-		ctx.audio_timeupdate_handler.call(audio);
+		ctx[10].call(audio);
 	}
 
 	return {
 		c() {
 			audio = element("audio");
-			if (ctx.played === void 0 || ctx.currentTime === void 0 || ctx.ended === void 0) add_render_callback(audio_timeupdate_handler);
-			if (ctx.duration === void 0) add_render_callback(() => ctx.audio_durationchange_handler.call(audio));
-			if (ctx.buffered === void 0) add_render_callback(() => ctx.audio_progress_handler.call(audio));
-			if (ctx.buffered === void 0 || ctx.seekable === void 0) add_render_callback(() => ctx.audio_loadedmetadata_handler.call(audio));
-			if (ctx.seeking === void 0) add_render_callback(() => ctx.audio_seeking_seeked_handler.call(audio));
-			if (ctx.ended === void 0) add_render_callback(() => ctx.audio_ended_handler.call(audio));
+			if (ctx[2] === void 0 || ctx[3] === void 0 || ctx[9] === void 0) add_render_callback(audio_timeupdate_handler);
+			if (ctx[4] === void 0) add_render_callback(() => ctx[11].call(audio));
+			if (ctx[0] === void 0) add_render_callback(() => ctx[13].call(audio));
+			if (ctx[0] === void 0 || ctx[1] === void 0) add_render_callback(() => ctx[14].call(audio));
+			if (ctx[8] === void 0) add_render_callback(() => ctx[17].call(audio));
+			if (ctx[9] === void 0) add_render_callback(() => ctx[18].call(audio));
 
 			dispose = [
 				listen(audio, "timeupdate", audio_timeupdate_handler),
-				listen(audio, "durationchange", ctx.audio_durationchange_handler),
-				listen(audio, "play", ctx.audio_play_pause_handler),
-				listen(audio, "pause", ctx.audio_play_pause_handler),
-				listen(audio, "progress", ctx.audio_progress_handler),
-				listen(audio, "loadedmetadata", ctx.audio_loadedmetadata_handler),
-				listen(audio, "volumechange", ctx.audio_volumechange_handler),
-				listen(audio, "ratechange", ctx.audio_ratechange_handler),
-				listen(audio, "seeking", ctx.audio_seeking_seeked_handler),
-				listen(audio, "seeked", ctx.audio_seeking_seeked_handler),
-				listen(audio, "ended", ctx.audio_ended_handler)
+				listen(audio, "durationchange", ctx[11]),
+				listen(audio, "play", ctx[12]),
+				listen(audio, "pause", ctx[12]),
+				listen(audio, "progress", ctx[13]),
+				listen(audio, "loadedmetadata", ctx[14]),
+				listen(audio, "volumechange", ctx[15]),
+				listen(audio, "ratechange", ctx[16]),
+				listen(audio, "seeking", ctx[17]),
+				listen(audio, "seeked", ctx[17]),
+				listen(audio, "ended", ctx[18])
 			];
 		},
 		m(target, anchor) {
 			insert(target, audio, anchor);
 
-			if (!isNaN(ctx.volume)) {
-				audio.volume = ctx.volume;
+			if (!isNaN(ctx[6])) {
+				audio.volume = ctx[6];
 			}
 
-			if (!isNaN(ctx.playbackRate)) {
-				audio.playbackRate = ctx.playbackRate;
+			if (!isNaN(ctx[7])) {
+				audio.playbackRate = ctx[7];
 			}
 		},
-		p(changed, ctx) {
-			if (!audio_updating && changed.currentTime && !isNaN(ctx.currentTime)) {
-				audio.currentTime = ctx.currentTime;
+		p(ctx, changed) {
+			if (!audio_updating && changed & 8 && !isNaN(ctx[3])) {
+				audio.currentTime = ctx[3];
 			}
 
-			if (changed.paused && audio_is_paused !== (audio_is_paused = ctx.paused)) {
+			if (changed & 32 && audio_is_paused !== (audio_is_paused = ctx[5])) {
 				audio[audio_is_paused ? "pause" : "play"]();
 			}
 
-			if (changed.volume && !isNaN(ctx.volume)) {
-				audio.volume = ctx.volume;
+			if (changed & 64 && !isNaN(ctx[6])) {
+				audio.volume = ctx[6];
 			}
 
-			if (changed.playbackRate && !isNaN(ctx.playbackRate)) {
-				audio.playbackRate = ctx.playbackRate;
+			if (changed & 128 && !isNaN(ctx[7])) {
+				audio.playbackRate = ctx[7];
 			}
 
 			audio_updating = false;
@@ -111,67 +111,67 @@ function instance($$self, $$props, $$invalidate) {
 		played = time_ranges_to_array(this.played);
 		currentTime = this.currentTime;
 		ended = this.ended;
-		$$invalidate("played", played);
-		$$invalidate("currentTime", currentTime);
-		$$invalidate("ended", ended);
+		$$invalidate(2, played);
+		$$invalidate(3, currentTime);
+		$$invalidate(9, ended);
 	}
 
 	function audio_durationchange_handler() {
 		duration = this.duration;
-		$$invalidate("duration", duration);
+		$$invalidate(4, duration);
 	}
 
 	function audio_play_pause_handler() {
 		paused = this.paused;
-		$$invalidate("paused", paused);
+		$$invalidate(5, paused);
 	}
 
 	function audio_progress_handler() {
 		buffered = time_ranges_to_array(this.buffered);
-		$$invalidate("buffered", buffered);
+		$$invalidate(0, buffered);
 	}
 
 	function audio_loadedmetadata_handler() {
 		buffered = time_ranges_to_array(this.buffered);
 		seekable = time_ranges_to_array(this.seekable);
-		$$invalidate("buffered", buffered);
-		$$invalidate("seekable", seekable);
+		$$invalidate(0, buffered);
+		$$invalidate(1, seekable);
 	}
 
 	function audio_volumechange_handler() {
 		volume = this.volume;
-		$$invalidate("volume", volume);
+		$$invalidate(6, volume);
 	}
 
 	function audio_ratechange_handler() {
 		playbackRate = this.playbackRate;
-		$$invalidate("playbackRate", playbackRate);
+		$$invalidate(7, playbackRate);
 	}
 
 	function audio_seeking_seeked_handler() {
 		seeking = this.seeking;
-		$$invalidate("seeking", seeking);
+		$$invalidate(8, seeking);
 	}
 
 	function audio_ended_handler() {
 		ended = this.ended;
-		$$invalidate("ended", ended);
+		$$invalidate(9, ended);
 	}
 
 	$$self.$set = $$props => {
-		if ("buffered" in $$props) $$invalidate("buffered", buffered = $$props.buffered);
-		if ("seekable" in $$props) $$invalidate("seekable", seekable = $$props.seekable);
-		if ("played" in $$props) $$invalidate("played", played = $$props.played);
-		if ("currentTime" in $$props) $$invalidate("currentTime", currentTime = $$props.currentTime);
-		if ("duration" in $$props) $$invalidate("duration", duration = $$props.duration);
-		if ("paused" in $$props) $$invalidate("paused", paused = $$props.paused);
-		if ("volume" in $$props) $$invalidate("volume", volume = $$props.volume);
-		if ("playbackRate" in $$props) $$invalidate("playbackRate", playbackRate = $$props.playbackRate);
-		if ("seeking" in $$props) $$invalidate("seeking", seeking = $$props.seeking);
-		if ("ended" in $$props) $$invalidate("ended", ended = $$props.ended);
+		if ("buffered" in $$props) $$invalidate(0, buffered = $$props.buffered);
+		if ("seekable" in $$props) $$invalidate(1, seekable = $$props.seekable);
+		if ("played" in $$props) $$invalidate(2, played = $$props.played);
+		if ("currentTime" in $$props) $$invalidate(3, currentTime = $$props.currentTime);
+		if ("duration" in $$props) $$invalidate(4, duration = $$props.duration);
+		if ("paused" in $$props) $$invalidate(5, paused = $$props.paused);
+		if ("volume" in $$props) $$invalidate(6, volume = $$props.volume);
+		if ("playbackRate" in $$props) $$invalidate(7, playbackRate = $$props.playbackRate);
+		if ("seeking" in $$props) $$invalidate(8, seeking = $$props.seeking);
+		if ("ended" in $$props) $$invalidate(9, ended = $$props.ended);
 	};
 
-	return {
+	return [
 		buffered,
 		seekable,
 		played,
@@ -191,7 +191,7 @@ function instance($$self, $$props, $$invalidate) {
 		audio_ratechange_handler,
 		audio_seeking_seeked_handler,
 		audio_ended_handler
-	};
+	];
 }
 
 class Component extends SvelteComponent {
@@ -200,15 +200,15 @@ class Component extends SvelteComponent {
 
 		init(this, options, instance, create_fragment, safe_not_equal, {
 			buffered: 0,
-			seekable: 0,
-			played: 0,
-			currentTime: 0,
-			duration: 0,
-			paused: 0,
-			volume: 0,
-			playbackRate: 0,
-			seeking: 0,
-			ended: 0
+			seekable: 1,
+			played: 2,
+			currentTime: 3,
+			duration: 4,
+			paused: 5,
+			volume: 6,
+			playbackRate: 7,
+			seeking: 8,
+			ended: 9
 		});
 	}
 }
diff --git a/test/js/samples/reactive-values-non-topologically-ordered/expected.js b/test/js/samples/reactive-values-non-topologically-ordered/expected.js
index 3d1b6aaae3..e4a4cc6605 100644
--- a/test/js/samples/reactive-values-non-topologically-ordered/expected.js
+++ b/test/js/samples/reactive-values-non-topologically-ordered/expected.js
@@ -7,20 +7,20 @@ function instance($$self, $$props, $$invalidate) {
 	let b;
 
 	$$self.$set = $$props => {
-		if ("x" in $$props) $$invalidate("x", x = $$props.x);
+		if ("x" in $$props) $$invalidate(0, x = $$props.x);
 	};
 
-	$$self.$$.update = (changed = { x: 1, b: 1 }) => {
-		if (changed.x) {
+	$$self.$$.update = () => {
+		if ($$self.$$.dirty & 1) {
 			$: $$invalidate("b", b = x);
 		}
 
-		if (changed.b) {
+		if ($$self.$$.dirty & 2) {
 			$: a = b;
 		}
 	};
 
-	return { x };
+	return [x];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/reactive-values-non-writable-dependencies/expected.js b/test/js/samples/reactive-values-non-writable-dependencies/expected.js
index 393af95df0..9c29f8510e 100644
--- a/test/js/samples/reactive-values-non-writable-dependencies/expected.js
+++ b/test/js/samples/reactive-values-non-writable-dependencies/expected.js
@@ -6,23 +6,23 @@ function instance($$self, $$props, $$invalidate) {
 	let { b = 2 } = $$props;
 
 	$$self.$set = $$props => {
-		if ("a" in $$props) $$invalidate("a", a = $$props.a);
-		if ("b" in $$props) $$invalidate("b", b = $$props.b);
+		if ("a" in $$props) $$invalidate(0, a = $$props.a);
+		if ("b" in $$props) $$invalidate(1, b = $$props.b);
 	};
 
-	$$self.$$.update = (changed = { a: 1, b: 1 }) => {
-		if (changed.a || changed.b) {
+	$$self.$$.update = () => {
+		if ($$self.$$.dirty & 3) {
 			$: console.log("max", Math.max(a, b));
 		}
 	};
 
-	return { a, b };
+	return [a, b];
 }
 
 class Component extends SvelteComponent {
 	constructor(options) {
 		super();
-		init(this, options, instance, null, safe_not_equal, { a: 0, b: 0 });
+		init(this, options, instance, null, safe_not_equal, { a: 0, b: 1 });
 	}
 }
 
diff --git a/test/js/samples/select-dynamic-value/expected.js b/test/js/samples/select-dynamic-value/expected.js
index da284d977a..efa4662297 100644
--- a/test/js/samples/select-dynamic-value/expected.js
+++ b/test/js/samples/select-dynamic-value/expected.js
@@ -32,7 +32,7 @@ function create_fragment(ctx) {
 			insert(target, select, anchor);
 			append(select, option0);
 			append(select, option1);
-			select_value_value = ctx.current;
+			select_value_value = ctx[0];
 
 			for (var i = 0; i < select.options.length; i += 1) {
 				var option = select.options[i];
@@ -43,8 +43,8 @@ function create_fragment(ctx) {
 				}
 			}
 		},
-		p(changed, ctx) {
-			if (changed.current && select_value_value !== (select_value_value = ctx.current)) {
+		p(ctx, changed) {
+			if (changed & 1 && select_value_value !== (select_value_value = ctx[0])) {
 				for (var i = 0; i < select.options.length; i += 1) {
 					var option = select.options[i];
 
@@ -67,10 +67,10 @@ function instance($$self, $$props, $$invalidate) {
 	let { current } = $$props;
 
 	$$self.$set = $$props => {
-		if ("current" in $$props) $$invalidate("current", current = $$props.current);
+		if ("current" in $$props) $$invalidate(0, current = $$props.current);
 	};
 
-	return { current };
+	return [current];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/src-attribute-check/expected.js b/test/js/samples/src-attribute-check/expected.js
index 8af33a962b..bf11b3821d 100644
--- a/test/js/samples/src-attribute-check/expected.js
+++ b/test/js/samples/src-attribute-check/expected.js
@@ -35,21 +35,21 @@ function create_fragment(ctx) {
 		},
 		h() {
 			attr(img0, "alt", "potato");
-			if (img0.src !== (img0_src_value = ctx.url)) attr(img0, "src", img0_src_value);
+			if (img0.src !== (img0_src_value = ctx[0])) attr(img0, "src", img0_src_value);
 			attr(img1, "alt", "potato");
-			if (img1.src !== (img1_src_value = "" + (ctx.slug + ".jpg"))) attr(img1, "src", img1_src_value);
+			if (img1.src !== (img1_src_value = "" + (ctx[1] + ".jpg"))) attr(img1, "src", img1_src_value);
 		},
 		m(target, anchor) {
 			insert(target, img0, anchor);
 			insert(target, t, anchor);
 			insert(target, img1, anchor);
 		},
-		p(changed, ctx) {
-			if (changed.url && img0.src !== (img0_src_value = ctx.url)) {
+		p(ctx, changed) {
+			if (changed & 1 && img0.src !== (img0_src_value = ctx[0])) {
 				attr(img0, "src", img0_src_value);
 			}
 
-			if (changed.slug && img1.src !== (img1_src_value = "" + (ctx.slug + ".jpg"))) {
+			if (changed & 2 && img1.src !== (img1_src_value = "" + (ctx[1] + ".jpg"))) {
 				attr(img1, "src", img1_src_value);
 			}
 		},
@@ -68,17 +68,17 @@ function instance($$self, $$props, $$invalidate) {
 	let { slug } = $$props;
 
 	$$self.$set = $$props => {
-		if ("url" in $$props) $$invalidate("url", url = $$props.url);
-		if ("slug" in $$props) $$invalidate("slug", slug = $$props.slug);
+		if ("url" in $$props) $$invalidate(0, url = $$props.url);
+		if ("slug" in $$props) $$invalidate(1, slug = $$props.slug);
 	};
 
-	return { url, slug };
+	return [url, slug];
 }
 
 class Component extends SvelteComponent {
 	constructor(options) {
 		super();
-		init(this, options, instance, create_fragment, safe_not_equal, { url: 0, slug: 0 });
+		init(this, options, instance, create_fragment, safe_not_equal, { url: 0, slug: 1 });
 	}
 }
 
diff --git a/test/js/samples/title/expected.js b/test/js/samples/title/expected.js
index 205f352950..b091b2a516 100644
--- a/test/js/samples/title/expected.js
+++ b/test/js/samples/title/expected.js
@@ -3,13 +3,13 @@ import { SvelteComponent, init, noop, safe_not_equal } from "svelte/internal";
 
 function create_fragment(ctx) {
 	let title_value;
-	document.title = title_value = "a " + ctx.custom + " title";
+	document.title = title_value = "a " + ctx[0] + " title";
 
 	return {
 		c: noop,
 		m: noop,
-		p(changed, ctx) {
-			if (changed.custom && title_value !== (title_value = "a " + ctx.custom + " title")) {
+		p(ctx, changed) {
+			if (changed & 1 && title_value !== (title_value = "a " + ctx[0] + " title")) {
 				document.title = title_value;
 			}
 		},
@@ -23,10 +23,10 @@ function instance($$self, $$props, $$invalidate) {
 	let { custom } = $$props;
 
 	$$self.$set = $$props => {
-		if ("custom" in $$props) $$invalidate("custom", custom = $$props.custom);
+		if ("custom" in $$props) $$invalidate(0, custom = $$props.custom);
 	};
 
-	return { custom };
+	return [custom];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/transition-local/expected.js b/test/js/samples/transition-local/expected.js
index 7fa88f4254..63f3ec4692 100644
--- a/test/js/samples/transition-local/expected.js
+++ b/test/js/samples/transition-local/expected.js
@@ -15,7 +15,7 @@ import {
 
 function create_if_block(ctx) {
 	let if_block_anchor;
-	let if_block = ctx.y && create_if_block_1(ctx);
+	let if_block = ctx[1] && create_if_block_1(ctx);
 
 	return {
 		c() {
@@ -26,8 +26,8 @@ function create_if_block(ctx) {
 			if (if_block) if_block.m(target, anchor);
 			insert(target, if_block_anchor, anchor);
 		},
-		p(changed, ctx) {
-			if (ctx.y) {
+		p(ctx, changed) {
+			if (ctx[1]) {
 				if (!if_block) {
 					if_block = create_if_block_1(ctx);
 					if_block.c();
@@ -80,7 +80,7 @@ function create_if_block_1(ctx) {
 
 function create_fragment(ctx) {
 	let if_block_anchor;
-	let if_block = ctx.x && create_if_block(ctx);
+	let if_block = ctx[0] && create_if_block(ctx);
 
 	return {
 		c() {
@@ -91,10 +91,10 @@ function create_fragment(ctx) {
 			if (if_block) if_block.m(target, anchor);
 			insert(target, if_block_anchor, anchor);
 		},
-		p(changed, ctx) {
-			if (ctx.x) {
+		p(ctx, changed) {
+			if (ctx[0]) {
 				if (if_block) {
-					if_block.p(changed, ctx);
+					if_block.p(ctx, changed);
 				} else {
 					if_block = create_if_block(ctx);
 					if_block.c();
@@ -115,7 +115,7 @@ function create_fragment(ctx) {
 }
 
 function foo() {
-	
+
 }
 
 function instance($$self, $$props, $$invalidate) {
@@ -123,17 +123,17 @@ function instance($$self, $$props, $$invalidate) {
 	let { y } = $$props;
 
 	$$self.$set = $$props => {
-		if ("x" in $$props) $$invalidate("x", x = $$props.x);
-		if ("y" in $$props) $$invalidate("y", y = $$props.y);
+		if ("x" in $$props) $$invalidate(0, x = $$props.x);
+		if ("y" in $$props) $$invalidate(1, y = $$props.y);
 	};
 
-	return { x, y };
+	return [x, y];
 }
 
 class Component extends SvelteComponent {
 	constructor(options) {
 		super();
-		init(this, options, instance, create_fragment, safe_not_equal, { x: 0, y: 0 });
+		init(this, options, instance, create_fragment, safe_not_equal, { x: 0, y: 1 });
 	}
 }
 
diff --git a/test/js/samples/transition-repeated-outro/expected.js b/test/js/samples/transition-repeated-outro/expected.js
index c40818dc4e..898bfb63a5 100644
--- a/test/js/samples/transition-repeated-outro/expected.js
+++ b/test/js/samples/transition-repeated-outro/expected.js
@@ -49,7 +49,7 @@ function create_if_block(ctx) {
 function create_fragment(ctx) {
 	let if_block_anchor;
 	let current;
-	let if_block = ctx.num < 5 && create_if_block(ctx);
+	let if_block = ctx[0] < 5 && create_if_block(ctx);
 
 	return {
 		c() {
@@ -61,8 +61,8 @@ function create_fragment(ctx) {
 			insert(target, if_block_anchor, anchor);
 			current = true;
 		},
-		p(changed, ctx) {
-			if (ctx.num < 5) {
+		p(ctx, changed) {
+			if (ctx[0] < 5) {
 				if (!if_block) {
 					if_block = create_if_block(ctx);
 					if_block.c();
@@ -101,10 +101,10 @@ function instance($$self, $$props, $$invalidate) {
 	let { num = 1 } = $$props;
 
 	$$self.$set = $$props => {
-		if ("num" in $$props) $$invalidate("num", num = $$props.num);
+		if ("num" in $$props) $$invalidate(0, num = $$props.num);
 	};
 
-	return { num };
+	return [num];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/unchanged-expression/expected.js b/test/js/samples/unchanged-expression/expected.js
index 231960bb49..f726af14a1 100644
--- a/test/js/samples/unchanged-expression/expected.js
+++ b/test/js/samples/unchanged-expression/expected.js
@@ -41,7 +41,7 @@ function create_fragment(ctx) {
 			div1 = element("div");
 			p3 = element("p");
 			t8 = text("Hello ");
-			t9 = text(ctx.world3);
+			t9 = text(ctx[0]);
 		},
 		m(target, anchor) {
 			insert(target, div0, anchor);
@@ -56,8 +56,8 @@ function create_fragment(ctx) {
 			append(p3, t8);
 			append(p3, t9);
 		},
-		p(changed, ctx) {
-			if (changed.world3) set_data(t9, ctx.world3);
+		p(ctx, changed) {
+			if (changed & 1) set_data(t9, ctx[0]);
 		},
 		i: noop,
 		o: noop,
@@ -76,10 +76,10 @@ function instance($$self, $$props, $$invalidate) {
 	const world3 = "world";
 
 	function foo() {
-		$$invalidate("world3", world3 = "svelte");
+		$$invalidate(0, world3 = "svelte");
 	}
 
-	return { world3 };
+	return [world3];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/unreferenced-state-not-invalidated/expected.js b/test/js/samples/unreferenced-state-not-invalidated/expected.js
index f0409c3cca..f85026bc9b 100644
--- a/test/js/samples/unreferenced-state-not-invalidated/expected.js
+++ b/test/js/samples/unreferenced-state-not-invalidated/expected.js
@@ -21,14 +21,14 @@ function create_fragment(ctx) {
 	return {
 		c() {
 			p = element("p");
-			t = text(ctx.y);
+			t = text(ctx[0]);
 		},
 		m(target, anchor) {
 			insert(target, p, anchor);
 			append(p, t);
 		},
-		p(changed, ctx) {
-			if (changed.y) set_data(t, ctx.y);
+		p(ctx, changed) {
+			if (changed & 1) set_data(t, ctx[0]);
 		},
 		i: noop,
 		o: noop,
@@ -44,7 +44,7 @@ function instance($$self, $$props, $$invalidate) {
 	onMount(() => {
 		const interval = setInterval(
 			() => {
-				$$invalidate("b", b += 1);
+				$$invalidate(1, b += 1);
 				c += 1;
 				console.log(b, c);
 			},
@@ -57,17 +57,17 @@ function instance($$self, $$props, $$invalidate) {
 	let x;
 	let y;
 
-	$$self.$$.update = (changed = { a: 1, b: 1 }) => {
-		if (changed.a) {
+	$$self.$$.update = () => {
+		if ($$self.$$.dirty === -1) {
 			$: x = a * 2;
 		}
 
-		if (changed.b) {
-			$: $$invalidate("y", y = b * 2);
+		if ($$self.$$.dirty & 2) {
+			$: $$invalidate(0, y = b * 2);
 		}
 	};
 
-	return { y };
+	return [y];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/use-elements-as-anchors/expected.js b/test/js/samples/use-elements-as-anchors/expected.js
index eeaba55ed0..fc77218bf8 100644
--- a/test/js/samples/use-elements-as-anchors/expected.js
+++ b/test/js/samples/use-elements-as-anchors/expected.js
@@ -112,11 +112,11 @@ function create_fragment(ctx) {
 	let t6;
 	let t7;
 	let if_block4_anchor;
-	let if_block0 = ctx.a && create_if_block_4(ctx);
-	let if_block1 = ctx.b && create_if_block_3(ctx);
-	let if_block2 = ctx.c && create_if_block_2(ctx);
-	let if_block3 = ctx.d && create_if_block_1(ctx);
-	let if_block4 = ctx.e && create_if_block(ctx);
+	let if_block0 = ctx[0] && create_if_block_4(ctx);
+	let if_block1 = ctx[1] && create_if_block_3(ctx);
+	let if_block2 = ctx[2] && create_if_block_2(ctx);
+	let if_block3 = ctx[3] && create_if_block_1(ctx);
+	let if_block4 = ctx[4] && create_if_block(ctx);
 
 	return {
 		c() {
@@ -155,66 +155,66 @@ function create_fragment(ctx) {
 			if (if_block4) if_block4.m(target, anchor);
 			insert(target, if_block4_anchor, anchor);
 		},
-		p(changed, ctx) {
-			if (ctx.a) {
+		p(ctx, changed) {
+			if (ctx[0]) {
 				if (!if_block0) {
 					if_block0 = create_if_block_4(ctx);
 					if_block0.c();
 					if_block0.m(div, t0);
 				} else {
-					
+
 				}
 			} else if (if_block0) {
 				if_block0.d(1);
 				if_block0 = null;
 			}
 
-			if (ctx.b) {
+			if (ctx[1]) {
 				if (!if_block1) {
 					if_block1 = create_if_block_3(ctx);
 					if_block1.c();
 					if_block1.m(div, t3);
 				} else {
-					
+
 				}
 			} else if (if_block1) {
 				if_block1.d(1);
 				if_block1 = null;
 			}
 
-			if (ctx.c) {
+			if (ctx[2]) {
 				if (!if_block2) {
 					if_block2 = create_if_block_2(ctx);
 					if_block2.c();
 					if_block2.m(div, t4);
 				} else {
-					
+
 				}
 			} else if (if_block2) {
 				if_block2.d(1);
 				if_block2 = null;
 			}
 
-			if (ctx.d) {
+			if (ctx[3]) {
 				if (!if_block3) {
 					if_block3 = create_if_block_1(ctx);
 					if_block3.c();
 					if_block3.m(div, null);
 				} else {
-					
+
 				}
 			} else if (if_block3) {
 				if_block3.d(1);
 				if_block3 = null;
 			}
 
-			if (ctx.e) {
+			if (ctx[4]) {
 				if (!if_block4) {
 					if_block4 = create_if_block(ctx);
 					if_block4.c();
 					if_block4.m(if_block4_anchor.parentNode, if_block4_anchor);
 				} else {
-					
+
 				}
 			} else if (if_block4) {
 				if_block4.d(1);
@@ -244,20 +244,20 @@ function instance($$self, $$props, $$invalidate) {
 	let { e } = $$props;
 
 	$$self.$set = $$props => {
-		if ("a" in $$props) $$invalidate("a", a = $$props.a);
-		if ("b" in $$props) $$invalidate("b", b = $$props.b);
-		if ("c" in $$props) $$invalidate("c", c = $$props.c);
-		if ("d" in $$props) $$invalidate("d", d = $$props.d);
-		if ("e" in $$props) $$invalidate("e", e = $$props.e);
+		if ("a" in $$props) $$invalidate(0, a = $$props.a);
+		if ("b" in $$props) $$invalidate(1, b = $$props.b);
+		if ("c" in $$props) $$invalidate(2, c = $$props.c);
+		if ("d" in $$props) $$invalidate(3, d = $$props.d);
+		if ("e" in $$props) $$invalidate(4, e = $$props.e);
 	};
 
-	return { a, b, c, d, e };
+	return [a, b, c, d, e];
 }
 
 class Component extends SvelteComponent {
 	constructor(options) {
 		super();
-		init(this, options, instance, create_fragment, safe_not_equal, { a: 0, b: 0, c: 0, d: 0, e: 0 });
+		init(this, options, instance, create_fragment, safe_not_equal, { a: 0, b: 1, c: 2, d: 3, e: 4 });
 	}
 }
 
diff --git a/test/js/samples/video-bindings/expected.js b/test/js/samples/video-bindings/expected.js
index e0e7707577..43241d51ff 100644
--- a/test/js/samples/video-bindings/expected.js
+++ b/test/js/samples/video-bindings/expected.js
@@ -29,27 +29,27 @@ function create_fragment(ctx) {
 			video_updating = true;
 		}
 
-		ctx.video_timeupdate_handler.call(video);
+		ctx[5].call(video);
 	}
 
 	return {
 		c() {
 			video = element("video");
-			add_render_callback(() => ctx.video_elementresize_handler.call(video));
-			if (ctx.videoHeight === void 0 || ctx.videoWidth === void 0) add_render_callback(() => ctx.video_resize_handler.call(video));
+			add_render_callback(() => ctx[4].call(video));
+			if (ctx[1] === void 0 || ctx[2] === void 0) add_render_callback(() => ctx[6].call(video));
 
 			dispose = [
 				listen(video, "timeupdate", video_timeupdate_handler),
-				listen(video, "resize", ctx.video_resize_handler)
+				listen(video, "resize", ctx[6])
 			];
 		},
 		m(target, anchor) {
 			insert(target, video, anchor);
-			video_resize_listener = add_resize_listener(video, ctx.video_elementresize_handler.bind(video));
+			video_resize_listener = add_resize_listener(video, ctx[4].bind(video));
 		},
-		p(changed, ctx) {
-			if (!video_updating && changed.currentTime && !isNaN(ctx.currentTime)) {
-				video.currentTime = ctx.currentTime;
+		p(ctx, changed) {
+			if (!video_updating && changed & 1 && !isNaN(ctx[0])) {
+				video.currentTime = ctx[0];
 			}
 
 			video_updating = false;
@@ -72,29 +72,29 @@ function instance($$self, $$props, $$invalidate) {
 
 	function video_elementresize_handler() {
 		offsetWidth = this.offsetWidth;
-		$$invalidate("offsetWidth", offsetWidth);
+		$$invalidate(3, offsetWidth);
 	}
 
 	function video_timeupdate_handler() {
 		currentTime = this.currentTime;
-		$$invalidate("currentTime", currentTime);
+		$$invalidate(0, currentTime);
 	}
 
 	function video_resize_handler() {
 		videoHeight = this.videoHeight;
 		videoWidth = this.videoWidth;
-		$$invalidate("videoHeight", videoHeight);
-		$$invalidate("videoWidth", videoWidth);
+		$$invalidate(1, videoHeight);
+		$$invalidate(2, videoWidth);
 	}
 
 	$$self.$set = $$props => {
-		if ("currentTime" in $$props) $$invalidate("currentTime", currentTime = $$props.currentTime);
-		if ("videoHeight" in $$props) $$invalidate("videoHeight", videoHeight = $$props.videoHeight);
-		if ("videoWidth" in $$props) $$invalidate("videoWidth", videoWidth = $$props.videoWidth);
-		if ("offsetWidth" in $$props) $$invalidate("offsetWidth", offsetWidth = $$props.offsetWidth);
+		if ("currentTime" in $$props) $$invalidate(0, currentTime = $$props.currentTime);
+		if ("videoHeight" in $$props) $$invalidate(1, videoHeight = $$props.videoHeight);
+		if ("videoWidth" in $$props) $$invalidate(2, videoWidth = $$props.videoWidth);
+		if ("offsetWidth" in $$props) $$invalidate(3, offsetWidth = $$props.offsetWidth);
 	};
 
-	return {
+	return [
 		currentTime,
 		videoHeight,
 		videoWidth,
@@ -102,7 +102,7 @@ function instance($$self, $$props, $$invalidate) {
 		video_elementresize_handler,
 		video_timeupdate_handler,
 		video_resize_handler
-	};
+	];
 }
 
 class Component extends SvelteComponent {
@@ -111,9 +111,9 @@ class Component extends SvelteComponent {
 
 		init(this, options, instance, create_fragment, safe_not_equal, {
 			currentTime: 0,
-			videoHeight: 0,
-			videoWidth: 0,
-			offsetWidth: 0
+			videoHeight: 1,
+			videoWidth: 2,
+			offsetWidth: 3
 		});
 	}
 }
diff --git a/test/js/samples/window-binding-online/expected.js b/test/js/samples/window-binding-online/expected.js
index d34e84330f..a2e0c0b89d 100644
--- a/test/js/samples/window-binding-online/expected.js
+++ b/test/js/samples/window-binding-online/expected.js
@@ -11,14 +11,11 @@ import {
 
 function create_fragment(ctx) {
 	let dispose;
-	add_render_callback(ctx.onlinestatuschanged);
+	add_render_callback(ctx[1]);
 
 	return {
 		c() {
-			dispose = [
-				listen(window, "online", ctx.onlinestatuschanged),
-				listen(window, "offline", ctx.onlinestatuschanged)
-			];
+			dispose = [listen(window, "online", ctx[1]), listen(window, "offline", ctx[1])];
 		},
 		m: noop,
 		p: noop,
@@ -34,10 +31,10 @@ function instance($$self, $$props, $$invalidate) {
 	let online;
 
 	function onlinestatuschanged() {
-		$$invalidate("online", online = navigator.onLine);
+		$$invalidate(0, online = navigator.onLine);
 	}
 
-	return { online, onlinestatuschanged };
+	return [online, onlinestatuschanged];
 }
 
 class Component extends SvelteComponent {
diff --git a/test/js/samples/window-binding-scroll/expected.js b/test/js/samples/window-binding-scroll/expected.js
index 85d894119b..254fb81966 100644
--- a/test/js/samples/window-binding-scroll/expected.js
+++ b/test/js/samples/window-binding-scroll/expected.js
@@ -26,19 +26,19 @@ function create_fragment(ctx) {
 	let t0;
 	let t1;
 	let dispose;
-	add_render_callback(ctx.onwindowscroll);
+	add_render_callback(ctx[1]);
 
 	return {
 		c() {
 			p = element("p");
 			t0 = text("scrolled to ");
-			t1 = text(ctx.y);
+			t1 = text(ctx[0]);
 
 			dispose = listen(window, "scroll", () => {
 				scrolling = true;
 				clearTimeout(scrolling_timeout);
 				scrolling_timeout = setTimeout(clear_scrolling, 100);
-				ctx.onwindowscroll();
+				ctx[1]();
 			});
 		},
 		m(target, anchor) {
@@ -46,15 +46,15 @@ function create_fragment(ctx) {
 			append(p, t0);
 			append(p, t1);
 		},
-		p(changed, ctx) {
-			if (changed.y && !scrolling) {
+		p(ctx, changed) {
+			if (changed & 1 && !scrolling) {
 				scrolling = true;
 				clearTimeout(scrolling_timeout);
-				scrollTo(window.pageXOffset, ctx.y);
+				scrollTo(window.pageXOffset, ctx[0]);
 				scrolling_timeout = setTimeout(clear_scrolling, 100);
 			}
 
-			if (changed.y) set_data(t1, ctx.y);
+			if (changed & 1) set_data(t1, ctx[0]);
 		},
 		i: noop,
 		o: noop,
@@ -69,14 +69,14 @@ function instance($$self, $$props, $$invalidate) {
 	let { y } = $$props;
 
 	function onwindowscroll() {
-		$$invalidate("y", y = window.pageYOffset)
+		$$invalidate(0, y = window.pageYOffset)
 	}
 
 	$$self.$set = $$props => {
-		if ("y" in $$props) $$invalidate("y", y = $$props.y);
+		if ("y" in $$props) $$invalidate(0, y = $$props.y);
 	};
 
-	return { y, onwindowscroll };
+	return [y, onwindowscroll];
 }
 
 class Component extends SvelteComponent {