From f244b80f7a80df54aa07f85c35720fa6ca880318 Mon Sep 17 00:00:00 2001
From: Conduitry <git@chor.date>
Date: Fri, 28 Feb 2020 23:07:34 -0500
Subject: [PATCH 01/23] docs: referenced_from_script var value (#4486)

---
 site/content/docs/04-compile-time.md | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/site/content/docs/04-compile-time.md b/site/content/docs/04-compile-time.md
index 0cb2ac3caf..f9bfa772fe 100644
--- a/site/content/docs/04-compile-time.md
+++ b/site/content/docs/04-compile-time.md
@@ -113,7 +113,8 @@ const {
 	* `module` is `true` if the value is declared in a `context="module"` script
 	* `mutated` is `true` if the value's properties are assigned to inside the component
 	* `reassigned` is `true` if the value is reassigned inside the component
-	* `referenced` is `true` if the value is used outside the declaration
+	* `referenced` is `true` if the value is used in the template
+	* `referenced_from_script` is `true` if the value is used in the `<script>` outside the declaration
 	* `writable` is `true` if the value was declared with `let` or `var` (but not `const`, `class` or `function`)
 * `stats` is an object used by the Svelte developer team for diagnosing the compiler. Avoid relying on it to stay the same!
 
@@ -144,6 +145,7 @@ compiled: {
 		mutated: boolean,
 		reassigned: boolean,
 		referenced: boolean,
+		referenced_from_script: boolean,
 		writable: boolean
 	}>,
 	stats: {

From cf660bdab1367aa9207df27338498a063223e959 Mon Sep 17 00:00:00 2001
From: Tan Li Hau <tanhauhau@users.noreply.github.com>
Date: Sat, 29 Feb 2020 22:17:06 +0800
Subject: [PATCH 02/23] mark module variables as mutated or reassigned (#4469)

---
 CHANGELOG.md                                |  1 +
 src/compiler/compile/Component.ts           |  9 ++-
 test/vars/samples/modules-vars/_config.js   | 72 +++++++++++++++++++++
 test/vars/samples/modules-vars/input.svelte | 18 ++++++
 4 files changed, 98 insertions(+), 2 deletions(-)
 create mode 100644 test/vars/samples/modules-vars/_config.js
 create mode 100644 test/vars/samples/modules-vars/input.svelte

diff --git a/CHANGELOG.md b/CHANGELOG.md
index ef5ba2307f..60553037e4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,7 @@
 
 ## Unreleased
 
+* In `vars` array, correctly indicate whether `module` variables are `mutated` or `reassigned` ([#3215](https://github.com/sveltejs/svelte/issues/3215))
 * Exclude global variables from `$capture_state` ([#4463](https://github.com/sveltejs/svelte/issues/4463))
 
 ## 3.19.1
diff --git a/src/compiler/compile/Component.ts b/src/compiler/compile/Component.ts
index 9822529ece..2569820464 100644
--- a/src/compiler/compile/Component.ts
+++ b/src/compiler/compile/Component.ts
@@ -780,7 +780,7 @@ export default class Component {
 
 		const component = this;
 		const { content } = script;
-		const { instance_scope, instance_scope_map: map } = this;
+		const { instance_scope, module_scope, instance_scope_map: map } = this;
 
 		let scope = instance_scope;
 
@@ -797,7 +797,12 @@ export default class Component {
 					const deep = assignee.type === 'MemberExpression';
 
 					names.forEach(name => {
-						if (scope.find_owner(name) === instance_scope) {
+						const scope_owner = scope.find_owner(name);
+						if (
+							scope_owner !== null
+								? scope_owner === instance_scope
+								: module_scope && module_scope.has(name)
+						) {
 							const variable = component.var_lookup.get(name);
 							variable[deep ? 'mutated' : 'reassigned'] = true;
 						}
diff --git a/test/vars/samples/modules-vars/_config.js b/test/vars/samples/modules-vars/_config.js
new file mode 100644
index 0000000000..e178941db6
--- /dev/null
+++ b/test/vars/samples/modules-vars/_config.js
@@ -0,0 +1,72 @@
+export default {
+	test(assert, vars) {
+		assert.deepEqual(vars, [
+			{
+				name: "a",
+				export_name: null,
+				injected: false,
+				module: true,
+				mutated: false,
+				reassigned: true,
+				referenced: false,
+				referenced_from_script: false,
+				writable: true
+			},
+			{
+				name: "b",
+				export_name: null,
+				injected: false,
+				module: true,
+				mutated: true,
+				reassigned: false,
+				referenced: false,
+				referenced_from_script: false,
+				writable: true
+			},
+			{
+				name: "c",
+				export_name: null,
+				injected: false,
+				module: true,
+				mutated: false,
+				reassigned: false,
+				referenced: false,
+				referenced_from_script: false,
+				writable: true
+			},
+			{
+				name: "d",
+				export_name: null,
+				injected: false,
+				module: true,
+				mutated: false,
+				reassigned: false,
+				referenced: false,
+				referenced_from_script: false,
+				writable: true
+			},
+			{
+				name: "c",
+				export_name: null,
+				injected: false,
+				module: false,
+				mutated: false,
+				reassigned: true,
+				referenced: false,
+				referenced_from_script: true,
+				writable: true
+			},
+			{
+				name: "foo",
+				export_name: null,
+				injected: false,
+				module: false,
+				mutated: false,
+				reassigned: false,
+				referenced: false,
+				referenced_from_script: false,
+				writable: false
+			}
+		]);
+	}
+};
diff --git a/test/vars/samples/modules-vars/input.svelte b/test/vars/samples/modules-vars/input.svelte
new file mode 100644
index 0000000000..8bbd5bdc5e
--- /dev/null
+++ b/test/vars/samples/modules-vars/input.svelte
@@ -0,0 +1,18 @@
+<script context='module'>
+	let a = {};
+	let b = {};
+	let c = {};
+	let d = {};
+</script>
+<script>
+	let c = {};
+
+	a = 1;
+	b.x = 1;
+
+	function foo() {
+		let d = {};
+		c = 1;
+		d.x = 1;
+	}
+</script>
\ No newline at end of file

From 8feb85a61fe32ec164ea0358e5966338c5c69e1d Mon Sep 17 00:00:00 2001
From: Tan Li Hau <tanhauhau@users.noreply.github.com>
Date: Sun, 1 Mar 2020 00:32:11 +0800
Subject: [PATCH 03/23] fix bitmask overflow for slot (#4485)

---
 CHANGELOG.md                                  |  1 +
 src/runtime/internal/utils.ts                 |  6 ++-
 .../bitmask-overflow-slot-3/Echo.svelte       |  9 ++++
 .../bitmask-overflow-slot-3/_config.js        | 30 ++++++++++++
 .../bitmask-overflow-slot-3/main.svelte       | 11 +++++
 .../bitmask-overflow-slot-4/Echo.svelte       | 11 +++++
 .../bitmask-overflow-slot-4/_config.js        | 41 ++++++++++++++++
 .../bitmask-overflow-slot-4/main.svelte       | 12 +++++
 .../bitmask-overflow-slot-5/Echo.svelte       | 13 +++++
 .../bitmask-overflow-slot-5/_config.js        | 49 +++++++++++++++++++
 .../bitmask-overflow-slot-5/main.svelte       | 13 +++++
 11 files changed, 195 insertions(+), 1 deletion(-)
 create mode 100644 test/runtime/samples/bitmask-overflow-slot-3/Echo.svelte
 create mode 100644 test/runtime/samples/bitmask-overflow-slot-3/_config.js
 create mode 100644 test/runtime/samples/bitmask-overflow-slot-3/main.svelte
 create mode 100644 test/runtime/samples/bitmask-overflow-slot-4/Echo.svelte
 create mode 100644 test/runtime/samples/bitmask-overflow-slot-4/_config.js
 create mode 100644 test/runtime/samples/bitmask-overflow-slot-4/main.svelte
 create mode 100644 test/runtime/samples/bitmask-overflow-slot-5/Echo.svelte
 create mode 100644 test/runtime/samples/bitmask-overflow-slot-5/_config.js
 create mode 100644 test/runtime/samples/bitmask-overflow-slot-5/main.svelte

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 60553037e4..8197888f57 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,7 @@
 
 * In `vars` array, correctly indicate whether `module` variables are `mutated` or `reassigned` ([#3215](https://github.com/sveltejs/svelte/issues/3215))
 * Exclude global variables from `$capture_state` ([#4463](https://github.com/sveltejs/svelte/issues/4463))
+* Fix bitmask overflow for slots ([#4481](https://github.com/sveltejs/svelte/issues/4481))
 
 ## 3.19.1
 
diff --git a/src/runtime/internal/utils.ts b/src/runtime/internal/utils.ts
index 4ba7e18c15..acb88c7669 100644
--- a/src/runtime/internal/utils.ts
+++ b/src/runtime/internal/utils.ts
@@ -83,7 +83,11 @@ export function get_slot_changes(definition, $$scope, dirty, fn) {
 	if (definition[2] && fn) {
 		const lets = definition[2](fn(dirty));
 
-		if (typeof $$scope.dirty === 'object') {
+		if ($$scope.dirty === undefined) {
+			return lets;
+		}
+
+		if (typeof lets === 'object') {
 			const merged = [];
 			const len = Math.max($$scope.dirty.length, lets.length);
 			for (let i = 0; i < len; i += 1) {
diff --git a/test/runtime/samples/bitmask-overflow-slot-3/Echo.svelte b/test/runtime/samples/bitmask-overflow-slot-3/Echo.svelte
new file mode 100644
index 0000000000..d3ecf142c9
--- /dev/null
+++ b/test/runtime/samples/bitmask-overflow-slot-3/Echo.svelte
@@ -0,0 +1,9 @@
+<script>
+	let dummy = 0;
+	function increment () {
+		dummy = 1;
+	}
+</script>
+
+<slot dummy={dummy}></slot>
+<button on:click={increment}></button>
\ No newline at end of file
diff --git a/test/runtime/samples/bitmask-overflow-slot-3/_config.js b/test/runtime/samples/bitmask-overflow-slot-3/_config.js
new file mode 100644
index 0000000000..93e548e5f7
--- /dev/null
+++ b/test/runtime/samples/bitmask-overflow-slot-3/_config.js
@@ -0,0 +1,30 @@
+export default {
+
+	html: `
+		<p>_0_1_2_3_4_5_6_7_8_9_10_11_12_13_14_15_16_17_18_19_20_21_22_23_24_25_26_27_28_29_30_31_32_33_34_35_36_37_38_39_40</p>
+		<p>0</p>
+		<button></button>
+	`,
+
+	async test({ assert, component, target, window }) {
+		// change from inside
+		const button = target.querySelector('button');
+		await button.dispatchEvent(new window.MouseEvent('click'));
+
+		assert.htmlEqual(target.innerHTML, `
+			<p>_0_1_2_3_4_5_6_7_8_9_10_11_12_13_14_15_16_17_18_19_20_21_22_23_24_25_26_27_28_29_30_31_32_33_34_35_36_37_38_39_40</p>
+			<p>1</p>
+			<button></button>
+		`);
+
+		// change from outside
+		component._0 = 'a';
+		component._40 = 'b';
+
+		assert.htmlEqual(target.innerHTML, `
+			<p>a_1_2_3_4_5_6_7_8_9_10_11_12_13_14_15_16_17_18_19_20_21_22_23_24_25_26_27_28_29_30_31_32_33_34_35_36_37_38_39b</p>
+			<p>1</p>
+			<button></button>
+		`);	
+	}
+};
\ No newline at end of file
diff --git a/test/runtime/samples/bitmask-overflow-slot-3/main.svelte b/test/runtime/samples/bitmask-overflow-slot-3/main.svelte
new file mode 100644
index 0000000000..ae798e4aee
--- /dev/null
+++ b/test/runtime/samples/bitmask-overflow-slot-3/main.svelte
@@ -0,0 +1,11 @@
+<script>
+	import Echo from './Echo.svelte';
+
+	export let _0 = '_0', _1 = '_1', _2 = '_2', _3 = '_3', _4 = '_4', _5 = '_5', _6 = '_6', _7 = '_7', _8 = '_8', _9 = '_9', _10 = '_10', _11 = '_11', _12 = '_12', _13 = '_13', _14 = '_14', _15 = '_15', _16 = '_16', _17 = '_17', _18 = '_18', _19 = '_19', _20 = '_20', _21 = '_21', _22 = '_22', _23 = '_23', _24 = '_24', _25 = '_25', _26 = '_26', _27 = '_27', _28 = '_28', _29 = '_29', _30 = '_30', _31 = '_31', _32 = '_32', _33 = '_33', _34 = '_34', _35 = '_35', _36 = '_36', _37 = '_37', _38 = '_38', _39 = '_39', _40 = '_40';
+</script>
+
+<Echo let:dummy>
+	<p>{_0}{_1}{_2}{_3}{_4}{_5}{_6}{_7}{_8}{_9}{_10}{_11}{_12}{_13}{_14}{_15}{_16}{_17}{_18}{_19}{_20}{_21}{_22}{_23}{_24}{_25}{_26}{_27}{_28}{_29}{_30}{_31}{_32}{_33}{_34}{_35}{_36}{_37}{_38}{_39}{_40}</p>
+	<p>{dummy}</p>
+</Echo>
+
diff --git a/test/runtime/samples/bitmask-overflow-slot-4/Echo.svelte b/test/runtime/samples/bitmask-overflow-slot-4/Echo.svelte
new file mode 100644
index 0000000000..2e1beda492
--- /dev/null
+++ b/test/runtime/samples/bitmask-overflow-slot-4/Echo.svelte
@@ -0,0 +1,11 @@
+<script>
+	export let _0 = '_0', _1 = '_1', _2 = '_2', _3 = '_3', _4 = '_4', _5 = '_5', _6 = '_6', _7 = '_7', _8 = '_8', _9 = '_9', _10 = '_10', _11 = '_11', _12 = '_12', _13 = '_13', _14 = '_14', _15 = '_15', _16 = '_16', _17 = '_17', _18 = '_18', _19 = '_19', _20 = '_20', _21 = '_21', _22 = '_22', _23 = '_23', _24 = '_24', _25 = '_25', _26 = '_26', _27 = '_27', _28 = '_28', _29 = '_29', _30 = '_30', _31 = '_31', _32 = '_32', _33 = '_33', _34 = '_34', _35 = '_35', _36 = '_36', _37 = '_37', _38 = '_38', _39 = '_39', _40 = '_40';	
+	let dummy = 0;
+	function increment () {
+		dummy = 1;
+	}
+</script>
+
+<p>{_0}{_1}{_2}{_3}{_4}{_5}{_6}{_7}{_8}{_9}{_10}{_11}{_12}{_13}{_14}{_15}{_16}{_17}{_18}{_19}{_20}{_21}{_22}{_23}{_24}{_25}{_26}{_27}{_28}{_29}{_30}{_31}{_32}{_33}{_34}{_35}{_36}{_37}{_38}{_39}{_40}</p>
+<slot dummy={dummy}></slot>
+<button on:click={increment}></button>
\ No newline at end of file
diff --git a/test/runtime/samples/bitmask-overflow-slot-4/_config.js b/test/runtime/samples/bitmask-overflow-slot-4/_config.js
new file mode 100644
index 0000000000..cdaa5de77f
--- /dev/null
+++ b/test/runtime/samples/bitmask-overflow-slot-4/_config.js
@@ -0,0 +1,41 @@
+export default {
+	html: `
+		<p>_0_1_2_3_4_5_6_7_8_9_10_11_12_13_14_15_16_17_18_19_20_21_22_23_24_25_26_27_28_29_30_31_32_33_34_35_36_37_38_39_40</p>
+		<p>0</p>
+		<p>0</p>
+		<button></button>
+	`,
+
+	async test({ assert, component, target, window }) {
+		// change from inside
+		const button = target.querySelector('button');
+		await button.dispatchEvent(new window.MouseEvent('click'));
+
+		assert.htmlEqual(target.innerHTML, `
+			<p>_0_1_2_3_4_5_6_7_8_9_10_11_12_13_14_15_16_17_18_19_20_21_22_23_24_25_26_27_28_29_30_31_32_33_34_35_36_37_38_39_40</p>
+			<p>0</p>
+			<p>1</p>
+			<button></button>
+		`);
+
+		// change from outside
+		component._0 = 'a';
+
+		assert.htmlEqual(target.innerHTML, `
+			<p>_0_1_2_3_4_5_6_7_8_9_10_11_12_13_14_15_16_17_18_19_20_21_22_23_24_25_26_27_28_29_30_31_32_33_34_35_36_37_38_39_40</p>
+			<p>a</p>
+			<p>1</p>
+			<button></button>
+		`);
+
+		// change from outside through props
+		component._40 = 'b';
+
+		assert.htmlEqual(target.innerHTML, `
+			<p>_0_1_2_3_4_5_6_7_8_9_10_11_12_13_14_15_16_17_18_19_20_21_22_23_24_25_26_27_28_29_30_31_32_33_34_35_36_37_38_39b</p>
+			<p>a</p>
+			<p>1</p>
+			<button></button>
+		`);
+	}
+};
\ No newline at end of file
diff --git a/test/runtime/samples/bitmask-overflow-slot-4/main.svelte b/test/runtime/samples/bitmask-overflow-slot-4/main.svelte
new file mode 100644
index 0000000000..7e02487a30
--- /dev/null
+++ b/test/runtime/samples/bitmask-overflow-slot-4/main.svelte
@@ -0,0 +1,12 @@
+<script>
+	import Echo from './Echo.svelte';
+
+	export let _0 = 0, _40;
+	
+</script>
+
+<Echo _40={_40} let:dummy>
+	<p>{_0}</p>
+	<p>{dummy}</p>
+</Echo>
+
diff --git a/test/runtime/samples/bitmask-overflow-slot-5/Echo.svelte b/test/runtime/samples/bitmask-overflow-slot-5/Echo.svelte
new file mode 100644
index 0000000000..dddb3f7642
--- /dev/null
+++ b/test/runtime/samples/bitmask-overflow-slot-5/Echo.svelte
@@ -0,0 +1,13 @@
+<script>
+	export let _0 = '_0', _1 = '_1', _2 = '_2', _3 = '_3', _4 = '_4', _5 = '_5', _6 = '_6', _7 = '_7', _8 = '_8', _9 = '_9', _10 = '_10', _11 = '_11', _12 = '_12', _13 = '_13', _14 = '_14', _15 = '_15', _16 = '_16', _17 = '_17', _18 = '_18', _19 = '_19', _20 = '_20', _21 = '_21', _22 = '_22', _23 = '_23', _24 = '_24', _25 = '_25', _26 = '_26', _27 = '_27', _28 = '_28', _29 = '_29', _30 = '_30', _31 = '_31', _32 = '_32', _33 = '_33', _34 = '_34', _35 = '_35', _36 = '_36', _37 = '_37', _38 = '_38', _39 = '_39', _40 = '_40';	
+	export let b = 'b';
+	let dummy = 0;
+	function increment () {
+		dummy = 1;
+	}
+</script>
+
+<p>{_0}{_1}{_2}{_3}{_4}{_5}{_6}{_7}{_8}{_9}{_10}{_11}{_12}{_13}{_14}{_15}{_16}{_17}{_18}{_19}{_20}{_21}{_22}{_23}{_24}{_25}{_26}{_27}{_28}{_29}{_30}{_31}{_32}{_33}{_34}{_35}{_36}{_37}{_38}{_39}{_40}</p>
+<p>{b}</p>
+<slot dummy={dummy}></slot>
+<button on:click={increment}></button>
\ No newline at end of file
diff --git a/test/runtime/samples/bitmask-overflow-slot-5/_config.js b/test/runtime/samples/bitmask-overflow-slot-5/_config.js
new file mode 100644
index 0000000000..7dedb8f7eb
--- /dev/null
+++ b/test/runtime/samples/bitmask-overflow-slot-5/_config.js
@@ -0,0 +1,49 @@
+export default {
+	html: `
+		<p>_0_1_2_3_4_5_6_7_8_9_10_11_12_13_14_15_16_17_18_19_20_21_22_23_24_25_26_27_28_29_30_31_32_33_34_35_36_37_38_39_40</p>
+		<p>b</p>
+		<p>-0-1-2-3-4-5-6-7-8-9-10-11-12-13-14-15-16-17-18-19-20-21-22-23-24-25-26-27-28-29-30-31-32-33-34-35-36-37-38-39-40</p>
+		<p>0</p>
+		<p>0</p>
+		<button></button>
+	`,
+
+	async test({ assert, component, target, window }) {
+		// change from inside
+		const button = target.querySelector('button');
+		await button.dispatchEvent(new window.MouseEvent('click'));
+
+		assert.htmlEqual(target.innerHTML, `
+			<p>_0_1_2_3_4_5_6_7_8_9_10_11_12_13_14_15_16_17_18_19_20_21_22_23_24_25_26_27_28_29_30_31_32_33_34_35_36_37_38_39_40</p>
+			<p>b</p>
+			<p>-0-1-2-3-4-5-6-7-8-9-10-11-12-13-14-15-16-17-18-19-20-21-22-23-24-25-26-27-28-29-30-31-32-33-34-35-36-37-38-39-40</p>
+			<p>0</p>
+			<p>1</p>
+			<button></button>
+		`);
+
+		// change from outside
+		component.a = 'AA';
+
+		assert.htmlEqual(target.innerHTML, `
+			<p>_0_1_2_3_4_5_6_7_8_9_10_11_12_13_14_15_16_17_18_19_20_21_22_23_24_25_26_27_28_29_30_31_32_33_34_35_36_37_38_39_40</p>
+			<p>b</p>
+			<p>-0-1-2-3-4-5-6-7-8-9-10-11-12-13-14-15-16-17-18-19-20-21-22-23-24-25-26-27-28-29-30-31-32-33-34-35-36-37-38-39-40</p>
+			<p>AA</p>
+			<p>1</p>
+			<button></button>
+		`);
+
+		// change from outside through props
+		component.b = 'BB';
+
+		assert.htmlEqual(target.innerHTML, `
+			<p>_0_1_2_3_4_5_6_7_8_9_10_11_12_13_14_15_16_17_18_19_20_21_22_23_24_25_26_27_28_29_30_31_32_33_34_35_36_37_38_39_40</p>
+			<p>BB</p>
+			<p>-0-1-2-3-4-5-6-7-8-9-10-11-12-13-14-15-16-17-18-19-20-21-22-23-24-25-26-27-28-29-30-31-32-33-34-35-36-37-38-39-40</p>
+			<p>AA</p>
+			<p>1</p>
+			<button></button>
+		`);
+	}
+};
\ No newline at end of file
diff --git a/test/runtime/samples/bitmask-overflow-slot-5/main.svelte b/test/runtime/samples/bitmask-overflow-slot-5/main.svelte
new file mode 100644
index 0000000000..b17d6f7bae
--- /dev/null
+++ b/test/runtime/samples/bitmask-overflow-slot-5/main.svelte
@@ -0,0 +1,13 @@
+<script>
+	import Echo from './Echo.svelte';
+	export let _0 = '-0', _1 = '-1', _2 = '-2', _3 = '-3', _4 = '-4', _5 = '-5', _6 = '-6', _7 = '-7', _8 = '-8', _9 = '-9', _10 = '-10', _11 = '-11', _12 = '-12', _13 = '-13', _14 = '-14', _15 = '-15', _16 = '-16', _17 = '-17', _18 = '-18', _19 = '-19', _20 = '-20', _21 = '-21', _22 = '-22', _23 = '-23', _24 = '-24', _25 = '-25', _26 = '-26', _27 = '-27', _28 = '-28', _29 = '-29', _30 = '-30', _31 = '-31', _32 = '-32', _33 = '-33', _34 = '-34', _35 = '-35', _36 = '-36', _37 = '-37', _38 = '-38', _39 = '-39', _40 = '-40';	
+	export let a = 0, b;
+	
+</script>
+
+<Echo b={b} let:dummy>
+	<p>{_0}{_1}{_2}{_3}{_4}{_5}{_6}{_7}{_8}{_9}{_10}{_11}{_12}{_13}{_14}{_15}{_16}{_17}{_18}{_19}{_20}{_21}{_22}{_23}{_24}{_25}{_26}{_27}{_28}{_29}{_30}{_31}{_32}{_33}{_34}{_35}{_36}{_37}{_38}{_39}{_40}</p>
+	<p>{a}</p>
+	<p>{dummy}</p>
+</Echo>
+

From 37a2d6c6eada0c4e893fb90f3d8faa6eb3036f6f Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Sat, 29 Feb 2020 11:34:18 -0500
Subject: [PATCH 04/23] Bump codecov from 3.5.0 to 3.6.5 (#4433)

Bumps [codecov](https://github.com/codecov/codecov-node) from 3.5.0 to 3.6.5.
- [Release notes](https://github.com/codecov/codecov-node/releases)
- [Commits](https://github.com/codecov/codecov-node/commits)

Signed-off-by: dependabot[bot] <support@github.com>
---
 package-lock.json | 111 +++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 96 insertions(+), 15 deletions(-)

diff --git a/package-lock.json b/package-lock.json
index 3b275078ec..f0f4e17422 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -137,6 +137,12 @@
         }
       }
     },
+    "@tootallnate/once": {
+      "version": "1.0.0",
+      "resolved": "https://registry.npmjs.org/@tootallnate/once/-/once-1.0.0.tgz",
+      "integrity": "sha512-KYyTT/T6ALPkIRd2Ge080X/BsXvy9O0hcWTtMWkPvwAwF99+vn6Dv4GzrFT/Nn1LePr+FFDbRXXlqmsy9lw2zA==",
+      "dev": true
+    },
     "@types/eslint-visitor-keys": {
       "version": "1.0.0",
       "resolved": "https://registry.npmjs.org/@types/eslint-visitor-keys/-/eslint-visitor-keys-1.0.0.tgz",
@@ -609,16 +615,16 @@
       }
     },
     "codecov": {
-      "version": "3.5.0",
-      "resolved": "https://registry.npmjs.org/codecov/-/codecov-3.5.0.tgz",
-      "integrity": "sha512-/OsWOfIHaQIr7aeZ4pY0UC1PZT6kimoKFOFYFNb6wxo3iw12nRrh+mNGH72rnXxNsq6SGfesVPizm/6Q3XqcFQ==",
+      "version": "3.6.5",
+      "resolved": "https://registry.npmjs.org/codecov/-/codecov-3.6.5.tgz",
+      "integrity": "sha512-v48WuDMUug6JXwmmfsMzhCHRnhUf8O3duqXvltaYJKrO1OekZWpB/eH6iIoaxMl8Qli0+u3OxptdsBOYiD7VAQ==",
       "dev": true,
       "requires": {
-        "argv": "^0.0.2",
-        "ignore-walk": "^3.0.1",
-        "js-yaml": "^3.13.1",
-        "teeny-request": "^3.11.3",
-        "urlgrey": "^0.4.4"
+        "argv": "0.0.2",
+        "ignore-walk": "3.0.3",
+        "js-yaml": "3.13.1",
+        "teeny-request": "6.0.1",
+        "urlgrey": "0.4.4"
       }
     },
     "color-convert": {
@@ -1670,6 +1676,37 @@
         "whatwg-encoding": "^1.0.1"
       }
     },
+    "http-proxy-agent": {
+      "version": "4.0.1",
+      "resolved": "https://registry.npmjs.org/http-proxy-agent/-/http-proxy-agent-4.0.1.tgz",
+      "integrity": "sha512-k0zdNgqWTGA6aeIRVpvfVob4fL52dTfaehylg0Y4UvSySvOq/Y+BOyPrgpUrA7HylqvU8vIZGsRuXmspskV0Tg==",
+      "dev": true,
+      "requires": {
+        "@tootallnate/once": "1",
+        "agent-base": "6",
+        "debug": "4"
+      },
+      "dependencies": {
+        "agent-base": {
+          "version": "6.0.0",
+          "resolved": "https://registry.npmjs.org/agent-base/-/agent-base-6.0.0.tgz",
+          "integrity": "sha512-j1Q7cSCqN+AwrmDd+pzgqc0/NpC655x2bUf5ZjRIO77DcNBFmh+OgRNzF6OKdCC9RSCb19fGd99+bhXFdkRNqw==",
+          "dev": true,
+          "requires": {
+            "debug": "4"
+          }
+        },
+        "debug": {
+          "version": "4.1.1",
+          "resolved": "https://registry.npmjs.org/debug/-/debug-4.1.1.tgz",
+          "integrity": "sha512-pYAIzeRo8J6KPEaJ0VWOh5Pzkbw/RetuzehGM7QRRX5he4fPHx2rdKMB256ehJCkX+XRQm16eZLqLNS8RSZXZw==",
+          "dev": true,
+          "requires": {
+            "ms": "^2.1.1"
+          }
+        }
+      }
+    },
     "http-signature": {
       "version": "1.2.0",
       "resolved": "https://registry.npmjs.org/http-signature/-/http-signature-1.2.0.tgz",
@@ -1707,9 +1744,9 @@
       "dev": true
     },
     "ignore-walk": {
-      "version": "3.0.1",
-      "resolved": "https://registry.npmjs.org/ignore-walk/-/ignore-walk-3.0.1.tgz",
-      "integrity": "sha512-DTVlMx3IYPe0/JJcYP7Gxg7ttZZu3IInhuEhbchuqneY9wWe5Ojy2mXLBaQFUQmo0AW2r3qG7m1mg86js+gnlQ==",
+      "version": "3.0.3",
+      "resolved": "https://registry.npmjs.org/ignore-walk/-/ignore-walk-3.0.3.tgz",
+      "integrity": "sha512-m7o6xuOaT1aqheYHKf8W6J5pYH85ZI9w077erOzLje3JsB1gkafkAhHHY19dqjulgIZHFm32Cp5uNZgcQqdJKw==",
       "dev": true,
       "requires": {
         "minimatch": "^3.0.4"
@@ -3362,6 +3399,15 @@
       "integrity": "sha1-NbCYdbT/SfJqd35QmzCQoyJr8ks=",
       "dev": true
     },
+    "stream-events": {
+      "version": "1.0.5",
+      "resolved": "https://registry.npmjs.org/stream-events/-/stream-events-1.0.5.tgz",
+      "integrity": "sha512-E1GUzBSgvct8Jsb3v2X15pjzN1tYebtbLaMg+eBOUOAxgbLoSbT2NS91ckc5lJD1KfLjId+jXJRgo0qnV5Nerg==",
+      "dev": true,
+      "requires": {
+        "stubs": "^3.0.0"
+      }
+    },
     "string-width": {
       "version": "3.1.0",
       "resolved": "https://registry.npmjs.org/string-width/-/string-width-3.1.0.tgz",
@@ -3409,6 +3455,12 @@
       "integrity": "sha512-VTyMAUfdm047mwKl+u79WIdrZxtFtn+nBxHeb844XBQ9uMNTuTHdx2hc5RiAJYqwTj3wc/xe5HLSdJSkJ+WfZw==",
       "dev": true
     },
+    "stubs": {
+      "version": "3.0.0",
+      "resolved": "https://registry.npmjs.org/stubs/-/stubs-3.0.0.tgz",
+      "integrity": "sha1-6NK6H6nJBXAwPAMLaQD31fiavls=",
+      "dev": true
+    },
     "sucrase": {
       "version": "3.10.1",
       "resolved": "https://registry.npmjs.org/sucrase/-/sucrase-3.10.1.tgz",
@@ -3449,14 +3501,43 @@
       }
     },
     "teeny-request": {
-      "version": "3.11.3",
-      "resolved": "https://registry.npmjs.org/teeny-request/-/teeny-request-3.11.3.tgz",
-      "integrity": "sha512-CKncqSF7sH6p4rzCgkb/z/Pcos5efl0DmolzvlqRQUNcpRIruOhY9+T1FsIlyEbfWd7MsFpodROOwHYh2BaXzw==",
+      "version": "6.0.1",
+      "resolved": "https://registry.npmjs.org/teeny-request/-/teeny-request-6.0.1.tgz",
+      "integrity": "sha512-TAK0c9a00ELOqLrZ49cFxvPVogMUFaWY8dUsQc/0CuQPGF+BOxOQzXfE413BAk2kLomwNplvdtMpeaeGWmoc2g==",
       "dev": true,
       "requires": {
-        "https-proxy-agent": "^2.2.1",
+        "http-proxy-agent": "^4.0.0",
+        "https-proxy-agent": "^4.0.0",
         "node-fetch": "^2.2.0",
+        "stream-events": "^1.0.5",
         "uuid": "^3.3.2"
+      },
+      "dependencies": {
+        "agent-base": {
+          "version": "5.1.1",
+          "resolved": "https://registry.npmjs.org/agent-base/-/agent-base-5.1.1.tgz",
+          "integrity": "sha512-TMeqbNl2fMW0nMjTEPOwe3J/PRFP4vqeoNuQMG0HlMrtm5QxKqdvAkZ1pRBQ/ulIyDD5Yq0nJ7YbdD8ey0TO3g==",
+          "dev": true
+        },
+        "debug": {
+          "version": "4.1.1",
+          "resolved": "https://registry.npmjs.org/debug/-/debug-4.1.1.tgz",
+          "integrity": "sha512-pYAIzeRo8J6KPEaJ0VWOh5Pzkbw/RetuzehGM7QRRX5he4fPHx2rdKMB256ehJCkX+XRQm16eZLqLNS8RSZXZw==",
+          "dev": true,
+          "requires": {
+            "ms": "^2.1.1"
+          }
+        },
+        "https-proxy-agent": {
+          "version": "4.0.0",
+          "resolved": "https://registry.npmjs.org/https-proxy-agent/-/https-proxy-agent-4.0.0.tgz",
+          "integrity": "sha512-zoDhWrkR3of1l9QAL8/scJZyLu8j/gBkcwcaQOZh7Gyh/+uJQzGVETdgT30akuwkpL8HTRfssqI3BZuV18teDg==",
+          "dev": true,
+          "requires": {
+            "agent-base": "5",
+            "debug": "4"
+          }
+        }
       }
     },
     "test-exclude": {

From b6aaa44880892a64712f629bff40f1433d92dfdb Mon Sep 17 00:00:00 2001
From: pushkin <mtrelis@outlook.com>
Date: Sat, 29 Feb 2020 18:43:53 +0100
Subject: [PATCH 05/23] check for unknown props even if component doesn't have
 writable props (#4454)

---
 src/compiler/compile/render_dom/index.ts             |  6 +++++-
 test/js/samples/debug-hoisted/expected.js            |  6 ++++++
 test/js/samples/debug-no-dependencies/expected.js    | 12 +++++++++++-
 test/js/samples/loop-protect/expected.js             |  8 ++++++++
 .../samples/dev-warning-unknown-props-2/Foo.svelte   |  1 +
 .../samples/dev-warning-unknown-props-2/_config.js   |  9 +++++++++
 .../samples/dev-warning-unknown-props-2/main.svelte  |  5 +++++
 7 files changed, 45 insertions(+), 2 deletions(-)
 create mode 100644 test/runtime/samples/dev-warning-unknown-props-2/Foo.svelte
 create mode 100644 test/runtime/samples/dev-warning-unknown-props-2/_config.js
 create mode 100644 test/runtime/samples/dev-warning-unknown-props-2/main.svelte

diff --git a/src/compiler/compile/render_dom/index.ts b/src/compiler/compile/render_dom/index.ts
index 71e8681646..3d1870ccaa 100644
--- a/src/compiler/compile/render_dom/index.ts
+++ b/src/compiler/compile/render_dom/index.ts
@@ -259,6 +259,9 @@ export default function dom(
 		inject_state;
 	if (has_invalidate) {
 		args.push(x`$$props`, x`$$invalidate`);
+	} else if (component.compile_options.dev) {
+		// $$props arg is still needed for unknown prop check
+		args.push(x`$$props`);
 	}
 
 	const has_create_fragment = block.has_content();
@@ -300,6 +303,7 @@ export default function dom(
 	const initial_context = renderer.context.slice(0, i + 1);
 
 	const has_definition = (
+		component.compile_options.dev ||
 		(instance_javascript && instance_javascript.length > 0) ||
 		filtered_props.length > 0 ||
 		uses_props ||
@@ -379,7 +383,7 @@ export default function dom(
 		});
 
 		let unknown_props_check;
-		if (component.compile_options.dev && !component.var_lookup.has('$$props') && writable_props.length) {
+		if (component.compile_options.dev && !component.var_lookup.has('$$props')) {
 			unknown_props_check = b`
 				const writable_props = [${writable_props.map(prop => x`'${prop.export_name}'`)}];
 				@_Object.keys($$props).forEach(key => {
diff --git a/test/js/samples/debug-hoisted/expected.js b/test/js/samples/debug-hoisted/expected.js
index c77168ef4f..190ff12c50 100644
--- a/test/js/samples/debug-hoisted/expected.js
+++ b/test/js/samples/debug-hoisted/expected.js
@@ -50,6 +50,12 @@ function create_fragment(ctx) {
 function instance($$self, $$props, $$invalidate) {
 	let obj = { x: 5 };
 	let kobzol = 5;
+	const writable_props = [];
+
+	Object.keys($$props).forEach(key => {
+		if (!~writable_props.indexOf(key) && key.slice(0, 2) !== "$$") console.warn(`<Component> was created with unknown prop '${key}'`);
+	});
+
 	$$self.$capture_state = () => ({ obj, kobzol });
 
 	$$self.$inject_state = $$props => {
diff --git a/test/js/samples/debug-no-dependencies/expected.js b/test/js/samples/debug-no-dependencies/expected.js
index 9985c814a2..a097869e74 100644
--- a/test/js/samples/debug-no-dependencies/expected.js
+++ b/test/js/samples/debug-no-dependencies/expected.js
@@ -134,10 +134,20 @@ function create_fragment(ctx) {
 	return block;
 }
 
+function instance($$self, $$props) {
+	const writable_props = [];
+
+	Object.keys($$props).forEach(key => {
+		if (!~writable_props.indexOf(key) && key.slice(0, 2) !== "$$") console.warn(`<Component> was created with unknown prop '${key}'`);
+	});
+
+	return [];
+}
+
 class Component extends SvelteComponentDev {
 	constructor(options) {
 		super(options);
-		init(this, options, null, create_fragment, safe_not_equal, {});
+		init(this, options, instance, create_fragment, safe_not_equal, {});
 
 		dispatch_dev("SvelteRegisterComponent", {
 			component: this,
diff --git a/test/js/samples/loop-protect/expected.js b/test/js/samples/loop-protect/expected.js
index 4eccaae7cb..f433bd61a9 100644
--- a/test/js/samples/loop-protect/expected.js
+++ b/test/js/samples/loop-protect/expected.js
@@ -6,6 +6,7 @@ import {
 	detach_dev,
 	dispatch_dev,
 	element,
+	globals,
 	init,
 	insert_dev,
 	loop_guard,
@@ -13,6 +14,7 @@ import {
 	safe_not_equal
 } from "svelte/internal";
 
+const { console: console_1 } = globals;
 const file = undefined;
 
 function create_fragment(ctx) {
@@ -102,6 +104,12 @@ function instance($$self, $$props, $$invalidate) {
 		} while (true);
 	}
 
+	const writable_props = [];
+
+	Object.keys($$props).forEach(key => {
+		if (!~writable_props.indexOf(key) && key.slice(0, 2) !== "$$") console_1.warn(`<Component> was created with unknown prop '${key}'`);
+	});
+
 	function div_binding($$value) {
 		binding_callbacks[$$value ? "unshift" : "push"](() => {
 			$$invalidate(0, node = $$value);
diff --git a/test/runtime/samples/dev-warning-unknown-props-2/Foo.svelte b/test/runtime/samples/dev-warning-unknown-props-2/Foo.svelte
new file mode 100644
index 0000000000..bc56c4d894
--- /dev/null
+++ b/test/runtime/samples/dev-warning-unknown-props-2/Foo.svelte
@@ -0,0 +1 @@
+Foo
diff --git a/test/runtime/samples/dev-warning-unknown-props-2/_config.js b/test/runtime/samples/dev-warning-unknown-props-2/_config.js
new file mode 100644
index 0000000000..9bff4a2a74
--- /dev/null
+++ b/test/runtime/samples/dev-warning-unknown-props-2/_config.js
@@ -0,0 +1,9 @@
+export default {
+	compileOptions: {
+		dev: true
+	},
+
+	warnings: [
+		`<Foo> was created with unknown prop 'fo'`
+	]
+};
diff --git a/test/runtime/samples/dev-warning-unknown-props-2/main.svelte b/test/runtime/samples/dev-warning-unknown-props-2/main.svelte
new file mode 100644
index 0000000000..1566cf3e41
--- /dev/null
+++ b/test/runtime/samples/dev-warning-unknown-props-2/main.svelte
@@ -0,0 +1,5 @@
+<script>
+	import Foo from './Foo.svelte';
+</script>
+
+<Foo fo="sho"/>

From 3f647a84f6c295334ac8309caa9724a3fa137ace Mon Sep 17 00:00:00 2001
From: Conduitry <git@chor.date>
Date: Sat, 29 Feb 2020 12:44:54 -0500
Subject: [PATCH 06/23] update changelog

---
 CHANGELOG.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8197888f57..3dd0aadf8b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,7 @@
 ## Unreleased
 
 * In `vars` array, correctly indicate whether `module` variables are `mutated` or `reassigned` ([#3215](https://github.com/sveltejs/svelte/issues/3215))
+* In `dev` mode, check for unknown props even if the component has no writable props ([#4323](https://github.com/sveltejs/svelte/issues/4323))
 * Exclude global variables from `$capture_state` ([#4463](https://github.com/sveltejs/svelte/issues/4463))
 * Fix bitmask overflow for slots ([#4481](https://github.com/sveltejs/svelte/issues/4481))
 

From 3a37de364bfbe75202d8e9fcef9e76b9ce6faaa2 Mon Sep 17 00:00:00 2001
From: Brian Takita <brian.takita@gmail.com>
Date: Sat, 29 Feb 2020 12:50:54 -0500
Subject: [PATCH 07/23] chore: more specific typings, and add README note about
 Yarn (#4483)

---
 README.md                                     |  2 ++
 src/compiler/compile/Component.ts             | 26 +++++++++----------
 src/compiler/compile/nodes/Let.ts             | 12 ++++-----
 .../compile/nodes/shared/Expression.ts        |  4 +--
 src/compiler/compile/render_dom/index.ts      |  4 +--
 5 files changed, 25 insertions(+), 23 deletions(-)

diff --git a/README.md b/README.md
index 3a43725637..fa725804a9 100644
--- a/README.md
+++ b/README.md
@@ -32,6 +32,8 @@ cd svelte
 npm install
 ```
 
+> Do not use Yarn to install the dependencies, as the specific package versions in `package-lock.json` are used to build and test Svelte.
+
 > Many tests depend on newlines being preserved as `<LF>`. On Windows, you can ensure this by cloning with:
 > ```bash
 > git -c core.autocrlf=false clone https://github.com/sveltejs/svelte.git
diff --git a/src/compiler/compile/Component.ts b/src/compiler/compile/Component.ts
index 2569820464..a7fe2992d1 100644
--- a/src/compiler/compile/Component.ts
+++ b/src/compiler/compile/Component.ts
@@ -239,7 +239,7 @@ export default class Component {
 			const program: any = { type: 'Program', body: result.js };
 
 			walk(program, {
-				enter: (node, parent, key) => {
+				enter: (node: Node, parent: Node, key) => {
 					if (node.type === 'Identifier') {
 						if (node.name[0] === '@') {
 							if (node.name[1] === '_') {
@@ -526,7 +526,7 @@ export default class Component {
 		if (!script) return;
 
 		walk(script.content, {
-			enter(node) {
+			enter(node: Node) {
 				if (node.type === 'LabeledStatement' && node.label.name === '$') {
 					component.warn(node as any, {
 						code: 'module-script-reactive-declaration',
@@ -715,7 +715,7 @@ export default class Component {
 		let scope_updated = false;
 
 		walk(content, {
-			enter(node, parent, prop, index) {
+			enter(node: Node, parent, prop, index) {
 				if (map.has(node)) {
 					scope = map.get(node);
 				}
@@ -741,7 +741,7 @@ export default class Component {
 				component.warn_on_undefined_store_value_references(node, parent, scope);
 			},
 
-			leave(node) {
+			leave(node: Node) {
 				// do it on leave, to prevent infinite loop
 				if (component.compile_options.dev && component.compile_options.loopGuardTimeout > 0) {
 					const to_replace_for_loop_protect = component.loop_protect(node, scope, component.compile_options.loopGuardTimeout);
@@ -785,7 +785,7 @@ export default class Component {
 		let scope = instance_scope;
 
 		walk(content, {
-			enter(node, parent) {
+			enter(node: Node, parent: Node) {
 				if (map.has(node)) {
 					scope = map.get(node);
 				}
@@ -818,7 +818,7 @@ export default class Component {
 				}
 			},
 
-			leave(node) {
+			leave(node: Node) {
 				if (map.has(node)) {
 					scope = scope.parent;
 				}
@@ -886,7 +886,7 @@ export default class Component {
 		let scope = instance_scope;
 
 		walk(this.ast.instance.content, {
-			enter(node, parent, key, index) {
+			enter(node: Node, parent, key, index) {
 				if (/Function/.test(node.type)) {
 					return this.skip();
 				}
@@ -963,7 +963,7 @@ export default class Component {
 				}
 			},
 
-			leave(node, parent, _key, index) {
+			leave(node: Node, parent, _key, index) {
 				if (map.has(node)) {
 					scope = scope.parent;
 				}
@@ -1064,7 +1064,7 @@ export default class Component {
 			walking.add(fn_declaration);
 
 			walk(fn_declaration, {
-				enter(node, parent) {
+				enter(node: Node, parent) {
 					if (!hoistable) return this.skip();
 
 					if (map.has(node)) {
@@ -1112,7 +1112,7 @@ export default class Component {
 					}
 				},
 
-				leave(node) {
+				leave(node: Node) {
 					if (map.has(node)) {
 						scope = scope.parent;
 					}
@@ -1155,7 +1155,7 @@ export default class Component {
 				const map = this.instance_scope_map;
 
 				walk(node.body, {
-					enter(node, parent) {
+					enter(node: Node, parent) {
 						if (map.has(node)) {
 							scope = map.get(node);
 						}
@@ -1195,7 +1195,7 @@ export default class Component {
 						}
 					},
 
-					leave(node) {
+					leave(node: Node) {
 						if (map.has(node)) {
 							scope = scope.parent;
 						}
@@ -1455,4 +1455,4 @@ function get_relative_path(from: string, to: string) {
 	}
 
 	return from_parts.concat(to_parts).join('/');
-}
\ No newline at end of file
+}
diff --git a/src/compiler/compile/nodes/Let.ts b/src/compiler/compile/nodes/Let.ts
index 7b92c5ce70..ef38cd36a8 100644
--- a/src/compiler/compile/nodes/Let.ts
+++ b/src/compiler/compile/nodes/Let.ts
@@ -1,7 +1,7 @@
 import Node from './shared/Node';
 import Component from '../Component';
 import { walk } from 'estree-walker';
-import { Identifier } from 'estree';
+import { BasePattern, Identifier } from 'estree';
 
 const applicable = new Set(['Identifier', 'ObjectExpression', 'ArrayExpression', 'Property']);
 
@@ -22,7 +22,7 @@ export default class Let extends Node {
 			this.value = info.expression;
 
 			walk(info.expression, {
-				enter(node) {
+				enter(node: Identifier|BasePattern) {
 					if (!applicable.has(node.type)) {
 						component.error(node as any, {
 							code: 'invalid-let',
@@ -31,16 +31,16 @@ export default class Let extends Node {
 					}
 
 					if (node.type === 'Identifier') {
-						names.push(node.name);
+						names.push((node as Identifier).name);
 					}
 
 					// slightly unfortunate hack
 					if (node.type === 'ArrayExpression') {
-						(node as any).type = 'ArrayPattern';
+						node.type = 'ArrayPattern';
 					}
 
 					if (node.type === 'ObjectExpression') {
-						(node as any).type = 'ObjectPattern';
+						node.type = 'ObjectPattern';
 					}
 				}
 			});
@@ -48,4 +48,4 @@ export default class Let extends Node {
 			names.push(this.name.name);
 		}
 	}
-}
\ No newline at end of file
+}
diff --git a/src/compiler/compile/nodes/shared/Expression.ts b/src/compiler/compile/nodes/shared/Expression.ts
index 1882c19267..db0908c3f4 100644
--- a/src/compiler/compile/nodes/shared/Expression.ts
+++ b/src/compiler/compile/nodes/shared/Expression.ts
@@ -143,7 +143,7 @@ export default class Expression {
 				}
 			},
 
-			leave(node) {
+			leave(node: Node) {
 				if (map.has(node)) {
 					scope = scope.parent;
 				}
@@ -338,7 +338,7 @@ export default class Expression {
 			});
 		}
 
-		return (this.manipulated = node);
+		return (this.manipulated = node as Node);
 	}
 }
 
diff --git a/src/compiler/compile/render_dom/index.ts b/src/compiler/compile/render_dom/index.ts
index 3d1870ccaa..d6da614276 100644
--- a/src/compiler/compile/render_dom/index.ts
+++ b/src/compiler/compile/render_dom/index.ts
@@ -200,7 +200,7 @@ export default function dom(
 		let execution_context: Node | null = null;
 
 		walk(component.ast.instance.content, {
-			enter(node) {
+			enter(node: Node) {
 				if (map.has(node)) {
 					scope = map.get(node) as Scope;
 
@@ -212,7 +212,7 @@ export default function dom(
 				}
 			},
 
-			leave(node) {
+			leave(node: Node) {
 				if (map.has(node)) {
 					scope = scope.parent;
 				}

From d802c3b266be31a509cb69f3a81666b20842f3ef Mon Sep 17 00:00:00 2001
From: Tan Li Hau <tanhauhau@users.noreply.github.com>
Date: Sun, 1 Mar 2020 11:47:50 +0800
Subject: [PATCH 08/23] in spread, distinguish never-updating and
 always-updating props (#4487)

---
 CHANGELOG.md                                  |  1 +
 .../wrappers/InlineComponent/index.ts         | 15 +++-
 .../samples/spread-component-2/Widget.svelte  | 13 ++++
 .../samples/spread-component-2/_config.js     | 76 +++++++++++++++++++
 .../samples/spread-component-2/main.svelte    | 12 +++
 5 files changed, 114 insertions(+), 3 deletions(-)
 create mode 100644 test/runtime/samples/spread-component-2/Widget.svelte
 create mode 100644 test/runtime/samples/spread-component-2/_config.js
 create mode 100644 test/runtime/samples/spread-component-2/main.svelte

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3dd0aadf8b..8cdc334868 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,7 @@
 ## Unreleased
 
 * In `vars` array, correctly indicate whether `module` variables are `mutated` or `reassigned` ([#3215](https://github.com/sveltejs/svelte/issues/3215))
+* Fix spread props not updating in certain situations ([#3521](https://github.com/sveltejs/svelte/issues/3521), [#4480](https://github.com/sveltejs/svelte/issues/4480))
 * In `dev` mode, check for unknown props even if the component has no writable props ([#4323](https://github.com/sveltejs/svelte/issues/4323))
 * Exclude global variables from `$capture_state` ([#4463](https://github.com/sveltejs/svelte/issues/4463))
 * Fix bitmask overflow for slots ([#4481](https://github.com/sveltejs/svelte/issues/4481))
diff --git a/src/compiler/compile/render_dom/wrappers/InlineComponent/index.ts b/src/compiler/compile/render_dom/wrappers/InlineComponent/index.ts
index 28b3c938f9..8088bbac91 100644
--- a/src/compiler/compile/render_dom/wrappers/InlineComponent/index.ts
+++ b/src/compiler/compile/render_dom/wrappers/InlineComponent/index.ts
@@ -224,7 +224,9 @@ export default class InlineComponentWrapper extends Wrapper {
 					const condition = dependencies.size > 0 && (dependencies.size !== all_dependencies.size)
 						? renderer.dirty(Array.from(dependencies))
 						: null;
+					const unchanged = dependencies.size === 0;
 
+					let change_object;
 					if (attr.is_spread) {
 						const value = attr.expression.manipulate(block);
 						initial_props.push(value);
@@ -233,13 +235,20 @@ export default class InlineComponentWrapper extends Wrapper {
 						if (attr.expression.node.type !== 'ObjectExpression') {
 							value_object = x`@get_spread_object(${value})`;
 						}
-						changes.push(condition ? x`${condition} && ${value_object}` : value_object);
+						change_object = value_object;
 					} else {
 						const obj = x`{ ${name}: ${attr.get_value(block)} }`;
 						initial_props.push(obj);
-
-						changes.push(condition ? x`${condition} && ${obj}` : x`${levels}[${i}]`);
+						change_object = obj;
 					}
+
+					changes.push(
+						unchanged
+							? x`${levels}[${i}]`
+							: condition
+							? x`${condition} && ${change_object}`
+							: change_object
+					);
 				});
 
 				block.chunks.init.push(b`
diff --git a/test/runtime/samples/spread-component-2/Widget.svelte b/test/runtime/samples/spread-component-2/Widget.svelte
new file mode 100644
index 0000000000..ae27aeb5e5
--- /dev/null
+++ b/test/runtime/samples/spread-component-2/Widget.svelte
@@ -0,0 +1,13 @@
+<script>
+	export let foo;
+	export let baz;
+	export let qux;
+	export let quux;
+	export let selected;
+</script>
+
+<p>foo: {foo}</p>
+<p>baz: {baz} ({typeof baz})</p>
+<p>qux: {qux}</p>
+<p>quux: {quux}</p>
+<p>selected: {selected}</p>
diff --git a/test/runtime/samples/spread-component-2/_config.js b/test/runtime/samples/spread-component-2/_config.js
new file mode 100644
index 0000000000..6d36e8e60d
--- /dev/null
+++ b/test/runtime/samples/spread-component-2/_config.js
@@ -0,0 +1,76 @@
+export default {
+	props: {
+		list: [{
+			foo: 'lol',
+			baz: 40 + 2,
+			qux: 5,
+			quux: 'core'
+		}, {
+			foo: 'lolzz',
+			baz: 50 + 2,
+			qux: 1,
+			quux: 'quuxx'
+		}],
+	},
+
+	html: `
+		<div>
+			<p>foo: lol</p>
+			<p>baz: 42 (number)</p>
+			<p>qux: 0</p>
+			<p>quux: core</p>
+			<p>selected: true</p>
+			<p>foo: lolzz</p>
+			<p>baz: 52 (number)</p>
+			<p>qux: 0</p>
+			<p>quux: quuxx</p>
+			<p>selected: false</p>
+		</div>
+	`,
+
+	test({ assert, component, target }) {
+		component.list = [{
+			foo: 'lol',
+			baz: 40 + 3,
+			qux: 8,
+			quux: 'heart'
+		}, {
+			foo: 'lolzz',
+			baz: 50 + 3,
+			qux: 8,
+			quux: 'heartxx'
+		}];
+
+		assert.htmlEqual(target.innerHTML, `
+			<div>
+				<p>foo: lol</p>
+				<p>baz: 43 (number)</p>
+				<p>qux: 0</p>
+				<p>quux: heart</p>
+				<p>selected: true</p>
+				<p>foo: lolzz</p>
+				<p>baz: 53 (number)</p>
+				<p>qux: 0</p>
+				<p>quux: heartxx</p>
+				<p>selected: false</p>
+			</div>
+		`);
+
+		component.qux = 1;
+
+		assert.htmlEqual(target.innerHTML, `
+			<div>
+				<p>foo: lol</p>
+				<p>baz: 43 (number)</p>
+				<p>qux: 1</p>
+				<p>quux: heart</p>
+				<p>selected: false</p>
+				<p>foo: lolzz</p>
+				<p>baz: 53 (number)</p>
+				<p>qux: 1</p>
+				<p>quux: heartxx</p>
+				<p>selected: true</p>
+			</div>
+		`);
+	}
+};
diff --git a/test/runtime/samples/spread-component-2/main.svelte b/test/runtime/samples/spread-component-2/main.svelte
new file mode 100644
index 0000000000..436e11f9c5
--- /dev/null
+++ b/test/runtime/samples/spread-component-2/main.svelte
@@ -0,0 +1,12 @@
+<script>
+	import Widget from './Widget.svelte';
+
+	export let list;
+	export let qux = 0;
+</script>
+
+<div>
+	{#each list as item, index (item.foo)}
+		<Widget {...item} qux={qux} selected={qux === index} />
+	{/each}
+</div>

From addea43e4f6c16e19083a78163210d7903543583 Mon Sep 17 00:00:00 2001
From: Conduitry <git@chor.date>
Date: Mon, 2 Mar 2020 09:01:00 -0500
Subject: [PATCH 09/23] docs: describe falsy and nullish attribute behavior
 (#4498)

---
 site/content/docs/02-template-syntax.md | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/site/content/docs/02-template-syntax.md b/site/content/docs/02-template-syntax.md
index 55b913ca94..d25b348254 100644
--- a/site/content/docs/02-template-syntax.md
+++ b/site/content/docs/02-template-syntax.md
@@ -58,6 +58,17 @@ Or they can *be* JavaScript expressions.
 
 ---
 
+Boolean attributes are included on the element if their value is [truthy](https://developer.mozilla.org/en-US/docs/Glossary/Truthy) and excluded if it's [falsy](https://developer.mozilla.org/en-US/docs/Glossary/Falsy).
+
+All other attributes are included unless their value is [nullish](https://developer.mozilla.org/en-US/docs/Glossary/Nullish) (`null` or `undefined`).
+
+```html
+<input required={false} placeholder="This input field is not required">
+<div title={null}>This div has no title attribute</div>
+```
+
+---
+
 An expression might include characters that would cause syntax highlighting to fail in regular HTML, so quoting the value is permitted. The quotes do not affect how the value is parsed:
 
 ```html

From 926a2aebd8915c53cf81b0b1e4038c2b1952e297 Mon Sep 17 00:00:00 2001
From: Tan Li Hau <tanhauhau@users.noreply.github.com>
Date: Wed, 4 Mar 2020 18:37:48 +0800
Subject: [PATCH 10/23] fix render fallback slot content due to whitespace
 (#4500)

---
 CHANGELOG.md                                  |  1 +
 src/compiler/compile/nodes/Text.ts            | 29 ++++++++
 .../compile/render_dom/wrappers/Fragment.ts   |  6 +-
 .../wrappers/InlineComponent/index.ts         | 25 ++++---
 .../compile/render_dom/wrappers/Text.ts       | 32 +-------
 .../compile/render_ssr/handlers/Element.ts    | 11 ++-
 .../render_ssr/handlers/InlineComponent.ts    | 23 ++++--
 .../utils/remove_whitespace_children.ts       | 73 +++++++++++++++++++
 src/compiler/utils/link.ts                    |  4 +
 .../Nested.svelte                             |  4 +
 .../component-slot-fallback-empty/_config.js  | 13 ++++
 .../component-slot-fallback-empty/main.svelte | 10 +++
 12 files changed, 178 insertions(+), 53 deletions(-)
 create mode 100644 src/compiler/compile/render_ssr/handlers/utils/remove_whitespace_children.ts
 create mode 100644 src/compiler/utils/link.ts
 create mode 100644 test/runtime/samples/component-slot-fallback-empty/Nested.svelte
 create mode 100644 test/runtime/samples/component-slot-fallback-empty/_config.js
 create mode 100644 test/runtime/samples/component-slot-fallback-empty/main.svelte

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8cdc334868..b0672d790e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,7 @@
 
 * In `vars` array, correctly indicate whether `module` variables are `mutated` or `reassigned` ([#3215](https://github.com/sveltejs/svelte/issues/3215))
 * Fix spread props not updating in certain situations ([#3521](https://github.com/sveltejs/svelte/issues/3521), [#4480](https://github.com/sveltejs/svelte/issues/4480))
+* Use the fallback content for slots if they are passed only whitespace ([#4092](https://github.com/sveltejs/svelte/issues/4092))
 * In `dev` mode, check for unknown props even if the component has no writable props ([#4323](https://github.com/sveltejs/svelte/issues/4323))
 * Exclude global variables from `$capture_state` ([#4463](https://github.com/sveltejs/svelte/issues/4463))
 * Fix bitmask overflow for slots ([#4481](https://github.com/sveltejs/svelte/issues/4481))
diff --git a/src/compiler/compile/nodes/Text.ts b/src/compiler/compile/nodes/Text.ts
index bfd28a5073..6b7432c22f 100644
--- a/src/compiler/compile/nodes/Text.ts
+++ b/src/compiler/compile/nodes/Text.ts
@@ -3,6 +3,18 @@ import Component from '../Component';
 import TemplateScope from './shared/TemplateScope';
 import { INode } from './interfaces';
 
+// Whitespace inside one of these elements will not result in
+// a whitespace node being created in any circumstances. (This
+// list is almost certainly very incomplete)
+const elements_without_text = new Set([
+	'audio',
+	'datalist',
+	'dl',
+	'optgroup',
+	'select',
+	'video',
+]);
+
 export default class Text extends Node {
 	type: 'Text';
 	data: string;
@@ -13,4 +25,21 @@ export default class Text extends Node {
 		this.data = info.data;
 		this.synthetic = info.synthetic || false;
 	}
+
+	should_skip() {
+		if (/\S/.test(this.data)) return false;
+
+		const parent_element = this.find_nearest(/(?:Element|InlineComponent|Head)/);
+		if (!parent_element) return false;
+
+		if (parent_element.type === 'Head') return true;
+		if (parent_element.type === 'InlineComponent') return parent_element.children.length === 1 && this === parent_element.children[0];
+
+		// svg namespace exclusions
+		if (/svg$/.test(parent_element.namespace)) {
+			if (this.prev && this.prev.type === "Element" && this.prev.name === "tspan") return false;
+		}
+
+		return parent_element.namespace || elements_without_text.has(parent_element.name);
+	}
 }
diff --git a/src/compiler/compile/render_dom/wrappers/Fragment.ts b/src/compiler/compile/render_dom/wrappers/Fragment.ts
index 224b17d43f..a0984b69b9 100644
--- a/src/compiler/compile/render_dom/wrappers/Fragment.ts
+++ b/src/compiler/compile/render_dom/wrappers/Fragment.ts
@@ -17,6 +17,7 @@ import { INode } from '../../nodes/interfaces';
 import Renderer from '../Renderer';
 import Block from '../Block';
 import { trim_start, trim_end } from '../../../utils/trim';
+import { link } from '../../../utils/link';
 import { Identifier } from 'estree';
 
 const wrappers = {
@@ -38,11 +39,6 @@ const wrappers = {
 	Window
 };
 
-function link(next: Wrapper, prev: Wrapper) {
-	prev.next = next;
-	if (next) next.prev = prev;
-}
-
 function trimmable_at(child: INode, next_sibling: Wrapper): boolean {
 	// Whitespace is trimmable if one of the following is true:
 	// The child and its sibling share a common nearest each block (not at an each block boundary)
diff --git a/src/compiler/compile/render_dom/wrappers/InlineComponent/index.ts b/src/compiler/compile/render_dom/wrappers/InlineComponent/index.ts
index 8088bbac91..8c8bd70696 100644
--- a/src/compiler/compile/render_dom/wrappers/InlineComponent/index.ts
+++ b/src/compiler/compile/render_dom/wrappers/InlineComponent/index.ts
@@ -138,11 +138,27 @@ export default class InlineComponentWrapper extends Wrapper {
 		const statements: Array<Node | Node[]> = [];
 		const updates: Array<Node | Node[]> = [];
 
+		if (this.fragment) {
+			this.renderer.add_to_context('$$scope', true);
+			const default_slot = this.slots.get('default');
+
+			this.fragment.nodes.forEach((child) => {
+				child.render(default_slot.block, null, x`#nodes` as unknown as Identifier);
+			});
+		}
+
 		let props;
 		const name_changes = block.get_unique_name(`${name.name}_changes`);
 
 		const uses_spread = !!this.node.attributes.find(a => a.is_spread);
 
+		// removing empty slot
+		for (const slot of this.slots.keys()) {
+			if (!this.slots.get(slot).block.has_content()) {
+				this.slots.delete(slot);
+			}
+		}
+
 		const initial_props = this.slots.size > 0
 			? [
 				p`$$slots: {
@@ -172,15 +188,6 @@ export default class InlineComponentWrapper extends Wrapper {
 			}
 		}
 
-		if (this.fragment) {
-			this.renderer.add_to_context('$$scope', true);
-			const default_slot = this.slots.get('default');
-
-			this.fragment.nodes.forEach((child) => {
-				child.render(default_slot.block, null, x`#nodes` as unknown as Identifier);
-			});
-		}
-
 		if (component.compile_options.dev) {
 			// TODO this is a terrible hack, but without it the component
 			// will complain that options.target is missing. This would
diff --git a/src/compiler/compile/render_dom/wrappers/Text.ts b/src/compiler/compile/render_dom/wrappers/Text.ts
index 1978cba0d7..7ef8aebd70 100644
--- a/src/compiler/compile/render_dom/wrappers/Text.ts
+++ b/src/compiler/compile/render_dom/wrappers/Text.ts
@@ -5,36 +5,6 @@ import Wrapper from './shared/Wrapper';
 import { x } from 'code-red';
 import { Identifier } from 'estree';
 
-// Whitespace inside one of these elements will not result in
-// a whitespace node being created in any circumstances. (This
-// list is almost certainly very incomplete)
-const elements_without_text = new Set([
-	'audio',
-	'datalist',
-	'dl',
-	'optgroup',
-	'select',
-	'video',
-]);
-
-// TODO this should probably be in Fragment
-function should_skip(node: Text) {
-	if (/\S/.test(node.data)) return false;
-
-	const parent_element = node.find_nearest(/(?:Element|InlineComponent|Head)/);
-	if (!parent_element) return false;
-
-	if (parent_element.type === 'Head') return true;
-	if (parent_element.type === 'InlineComponent') return parent_element.children.length === 1 && node === parent_element.children[0];
-
-	// svg namespace exclusions
-	if (/svg$/.test(parent_element.namespace)) {
-		if (node.prev && node.prev.type === "Element" && node.prev.name === "tspan") return false;
-	}
-
-	return parent_element.namespace || elements_without_text.has(parent_element.name);
-}
-
 export default class TextWrapper extends Wrapper {
 	node: Text;
 	data: string;
@@ -50,7 +20,7 @@ export default class TextWrapper extends Wrapper {
 	) {
 		super(renderer, block, parent, node);
 
-		this.skip = should_skip(this.node);
+		this.skip = this.node.should_skip();
 		this.data = data;
 		this.var = (this.skip ? null : x`t`) as unknown as Identifier;
 	}
diff --git a/src/compiler/compile/render_ssr/handlers/Element.ts b/src/compiler/compile/render_ssr/handlers/Element.ts
index 6e6a61974a..ad5c421bc4 100644
--- a/src/compiler/compile/render_ssr/handlers/Element.ts
+++ b/src/compiler/compile/render_ssr/handlers/Element.ts
@@ -6,10 +6,14 @@ import Renderer, { RenderOptions } from '../Renderer';
 import Element from '../../nodes/Element';
 import { x } from 'code-red';
 import Expression from '../../nodes/shared/Expression';
+import remove_whitespace_children from './utils/remove_whitespace_children';
 
 export default function(node: Element, renderer: Renderer, options: RenderOptions & {
 	slot_scopes: Map<any, any>;
 }) {
+
+	const children = remove_whitespace_children(node.children, node.next);
+
 	// awkward special case
 	let node_contents;
 
@@ -133,7 +137,7 @@ export default function(node: Element, renderer: Renderer, options: RenderOption
 	if (node_contents !== undefined) {
 		if (contenteditable) {
 			renderer.push();
-			renderer.render(node.children, options);
+			renderer.render(children, options);
 			const result = renderer.pop();
 
 			renderer.add_expression(x`($$value => $$value === void 0 ? ${result} : $$value)(${node_contents})`);
@@ -145,7 +149,7 @@ export default function(node: Element, renderer: Renderer, options: RenderOption
 			renderer.add_string(`</${node.name}>`);
 		}
 	} else if (slot && nearest_inline_component) {
-		renderer.render(node.children, options);
+		renderer.render(children, options);
 
 		if (!is_void(node.name)) {
 			renderer.add_string(`</${node.name}>`);
@@ -163,10 +167,11 @@ export default function(node: Element, renderer: Renderer, options: RenderOption
 			output: renderer.pop()
 		});
 	} else {
-		renderer.render(node.children, options);
+		renderer.render(children, options);
 
 		if (!is_void(node.name)) {
 			renderer.add_string(`</${node.name}>`);
 		}
 	}
 }
+
diff --git a/src/compiler/compile/render_ssr/handlers/InlineComponent.ts b/src/compiler/compile/render_ssr/handlers/InlineComponent.ts
index 5c4d9c73b8..37f05a941c 100644
--- a/src/compiler/compile/render_ssr/handlers/InlineComponent.ts
+++ b/src/compiler/compile/render_ssr/handlers/InlineComponent.ts
@@ -2,6 +2,7 @@ import { string_literal } from '../../utils/stringify';
 import Renderer, { RenderOptions } from '../Renderer';
 import { get_slot_scope } from './shared/get_slot_scope';
 import InlineComponent from '../../nodes/InlineComponent';
+import remove_whitespace_children from './utils/remove_whitespace_children';
 import { p, x } from 'code-red';
 
 function get_prop_value(attribute) {
@@ -67,12 +68,14 @@ export default function(node: InlineComponent, renderer: Renderer, options: Rend
 
 	const slot_fns = [];
 
-	if (node.children.length) {
+	const children = remove_whitespace_children(node.children, node.next);
+
+	if (children.length) {
 		const slot_scopes = new Map();
 
 		renderer.push();
 
-		renderer.render(node.children, Object.assign({}, options, {
+		renderer.render(children, Object.assign({}, options, {
 			slot_scopes
 		}));
 
@@ -82,9 +85,11 @@ export default function(node: InlineComponent, renderer: Renderer, options: Rend
 		});
 
 		slot_scopes.forEach(({ input, output }, name) => {
-			slot_fns.push(
-				p`${name}: (${input}) => ${output}`
-			);
+			if (!is_empty_template_literal(output)) {
+				slot_fns.push(
+					p`${name}: (${input}) => ${output}`
+				);
+			}
 		});
 	}
 
@@ -94,3 +99,11 @@ export default function(node: InlineComponent, renderer: Renderer, options: Rend
 
 	renderer.add_expression(x`@validate_component(${expression}, "${node.name}").$$render($$result, ${props}, ${bindings}, ${slots})`);
 }
+
+function is_empty_template_literal(template_literal) {
+	return (
+		template_literal.expressions.length === 0 &&
+		template_literal.quasis.length === 1 &&
+		template_literal.quasis[0].value.raw === ""
+	);
+}
\ No newline at end of file
diff --git a/src/compiler/compile/render_ssr/handlers/utils/remove_whitespace_children.ts b/src/compiler/compile/render_ssr/handlers/utils/remove_whitespace_children.ts
new file mode 100644
index 0000000000..b6c1bf493a
--- /dev/null
+++ b/src/compiler/compile/render_ssr/handlers/utils/remove_whitespace_children.ts
@@ -0,0 +1,73 @@
+import { INode } from '../../../nodes/interfaces';
+import { trim_end, trim_start } from '../../../../utils/trim';
+import { link } from '../../../../utils/link';
+
+// similar logic from `compile/render_dom/wrappers/Fragment`
+// We want to remove trailing whitespace inside an element/component/block,
+// *unless* there is no whitespace between this node and its next sibling
+export default function remove_whitespace_children(children: INode[], next?: INode): INode[] {
+	const nodes: INode[] = [];
+	let last_child: INode;
+	let i = children.length;
+	while (i--) {
+		const child = children[i];
+
+		if (child.type === 'Text') {
+			if (child.should_skip()) {
+				continue;
+			}
+
+			let { data } = child;
+
+			if (nodes.length === 0) {
+				const should_trim = next
+					? next.type === 'Text' &&
+					  /^\s/.test(next.data) &&
+					  trimmable_at(child, next)
+					: !child.has_ancestor('EachBlock');
+
+				if (should_trim) {
+					data = trim_end(data);
+					if (!data) continue;
+				}
+			}
+
+			// glue text nodes (which could e.g. be separated by comments) together
+			if (last_child && last_child.type === 'Text') {
+				last_child.data = data + last_child.data;
+				continue;
+			}
+
+			nodes.unshift(child);
+			link(last_child, last_child = child);
+		} else {
+			nodes.unshift(child);
+			link(last_child, last_child = child);
+		}
+	}
+
+	const first = nodes[0];
+	if (first && first.type === 'Text') {
+		first.data = trim_start(first.data);
+		if (!first.data) {
+			first.var = null;
+			nodes.shift();
+
+			if (nodes[0]) {
+				nodes[0].prev = null;
+			}
+		}
+	}
+
+	return nodes;
+}
+
+function trimmable_at(child: INode, next_sibling: INode): boolean {
+	// Whitespace is trimmable if one of the following is true:
+	// The child and its sibling share a common nearest each block (not at an each block boundary)
+	// The next sibling's previous node is an each block
+	return (
+		next_sibling.find_nearest(/EachBlock/) ===
+			child.find_nearest(/EachBlock/) || next_sibling.prev.type === 'EachBlock'
+	);
+}
diff --git a/src/compiler/utils/link.ts b/src/compiler/utils/link.ts
new file mode 100644
index 0000000000..7cdef75d94
--- /dev/null
+++ b/src/compiler/utils/link.ts
@@ -0,0 +1,4 @@
+export function link<T extends { next?: T; prev?: T }>(next: T, prev: T) {
+	prev.next = next;
+	if (next) next.prev = prev;
+}
diff --git a/test/runtime/samples/component-slot-fallback-empty/Nested.svelte b/test/runtime/samples/component-slot-fallback-empty/Nested.svelte
new file mode 100644
index 0000000000..9e6683feb7
--- /dev/null
+++ b/test/runtime/samples/component-slot-fallback-empty/Nested.svelte
@@ -0,0 +1,4 @@
+<div>
+	<slot><p class='default'>default fallback content</p></slot>
+	<slot name='bar'>bar fallback</slot>
+</div>
\ No newline at end of file
diff --git a/test/runtime/samples/component-slot-fallback-empty/_config.js b/test/runtime/samples/component-slot-fallback-empty/_config.js
new file mode 100644
index 0000000000..2e153d24db
--- /dev/null
+++ b/test/runtime/samples/component-slot-fallback-empty/_config.js
@@ -0,0 +1,13 @@
+export default {
+	html: `
+	<div>
+		<p class="default">default fallback content</p>
+		<input slot="bar">
+	</div>
+	
+	<div>
+		<p class="default">default fallback content</p>
+		bar fallback
+	</div>
+	`
+};
diff --git a/test/runtime/samples/component-slot-fallback-empty/main.svelte b/test/runtime/samples/component-slot-fallback-empty/main.svelte
new file mode 100644
index 0000000000..7ae5f4c5d7
--- /dev/null
+++ b/test/runtime/samples/component-slot-fallback-empty/main.svelte
@@ -0,0 +1,10 @@
+<script>
+	import Nested from "./Nested.svelte";
+</script>
+
+<Nested>
+	<input slot="bar">
+</Nested>
+
+<Nested>
+</Nested>

From f2ee7efb942d68e22881fb042ff6870473c2d82e Mon Sep 17 00:00:00 2001
From: Conduitry <git@chor.date>
Date: Wed, 4 Mar 2020 19:56:13 -0500
Subject: [PATCH 11/23] add dev runtime warning for unknown slot names (#4501)

---
 CHANGELOG.md                                             | 1 +
 src/compiler/compile/render_dom/Block.ts                 | 3 +--
 src/compiler/compile/render_dom/index.ts                 | 5 +++--
 src/runtime/internal/dev.ts                              | 7 +++++++
 test/js/samples/capture-inject-state/expected.js         | 4 ++++
 test/js/samples/debug-empty/expected.js                  | 6 +++++-
 test/js/samples/debug-foo-bar-baz-things/expected.js     | 6 +++++-
 test/js/samples/debug-foo/expected.js                    | 6 +++++-
 test/js/samples/debug-hoisted/expected.js                | 5 ++++-
 test/js/samples/debug-no-dependencies/expected.js        | 5 ++++-
 .../dev-warning-missing-data-computed/expected.js        | 6 +++++-
 test/js/samples/loop-protect/expected.js                 | 8 ++++++--
 .../runtime/samples/component-slot-warning/Nested.svelte | 1 +
 test/runtime/samples/component-slot-warning/_config.js   | 9 +++++++++
 test/runtime/samples/component-slot-warning/main.svelte  | 7 +++++++
 15 files changed, 67 insertions(+), 12 deletions(-)
 create mode 100644 test/runtime/samples/component-slot-warning/Nested.svelte
 create mode 100644 test/runtime/samples/component-slot-warning/_config.js
 create mode 100644 test/runtime/samples/component-slot-warning/main.svelte

diff --git a/CHANGELOG.md b/CHANGELOG.md
index b0672d790e..f39308e5ff 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,7 @@
 
 ## Unreleased
 
+* In `dev` mode, display a runtime warning when a component is passed an unexpected slot ([#1020](https://github.com/sveltejs/svelte/issues/1020), [#1447](https://github.com/sveltejs/svelte/issues/1447))
 * In `vars` array, correctly indicate whether `module` variables are `mutated` or `reassigned` ([#3215](https://github.com/sveltejs/svelte/issues/3215))
 * Fix spread props not updating in certain situations ([#3521](https://github.com/sveltejs/svelte/issues/3521), [#4480](https://github.com/sveltejs/svelte/issues/4480))
 * Use the fallback content for slots if they are passed only whitespace ([#4092](https://github.com/sveltejs/svelte/issues/4092))
diff --git a/src/compiler/compile/render_dom/Block.ts b/src/compiler/compile/render_dom/Block.ts
index 62bdc5bdd9..2da77d3fbf 100644
--- a/src/compiler/compile/render_dom/Block.ts
+++ b/src/compiler/compile/render_dom/Block.ts
@@ -412,8 +412,7 @@ export default class Block {
 	}
 
 	has_content() {
-		return this.renderer.options.dev ||
-			this.first ||
+		return this.first ||
 			this.event_listeners.length > 0 ||
 			this.chunks.intro.length > 0 ||
 			this.chunks.outro.length > 0  ||
diff --git a/src/compiler/compile/render_dom/index.ts b/src/compiler/compile/render_dom/index.ts
index d6da614276..fc3c94a2be 100644
--- a/src/compiler/compile/render_dom/index.ts
+++ b/src/compiler/compile/render_dom/index.ts
@@ -264,7 +264,7 @@ export default function dom(
 		args.push(x`$$props`);
 	}
 
-	const has_create_fragment = block.has_content();
+	const has_create_fragment = component.compile_options.dev || block.has_content();
 	if (has_create_fragment) {
 		body.push(b`
 			function create_fragment(#ctx) {
@@ -412,7 +412,8 @@ export default function dom(
 
 				${unknown_props_check}
 
-				${component.slots.size ? b`let { $$slots = {}, $$scope } = $$props;` : null}
+				${component.slots.size || component.compile_options.dev ? b`let { $$slots = {}, $$scope } = $$props;` : null}
+				${component.compile_options.dev && b`@validate_slots('${component.tag}', $$slots, [${[...component.slots.keys()].map(key => `'${key}'`).join(',')}]);`}
 
 				${renderer.binding_groups.length > 0 && b`const $$binding_groups = [${renderer.binding_groups.map(_ => x`[]`)}];`}
 
diff --git a/src/runtime/internal/dev.ts b/src/runtime/internal/dev.ts
index 8aefc88ba7..751f1f802b 100644
--- a/src/runtime/internal/dev.ts
+++ b/src/runtime/internal/dev.ts
@@ -89,6 +89,13 @@ export function validate_each_argument(arg) {
 	}
 }
 
+export function validate_slots(name, slot, keys) {
+	for (const slot_key of Object.keys(slot)) {
+		if (!~keys.indexOf(slot_key)) {
+			console.warn(`<${name}> received an unexpected slot "${slot_key}".`);
+		}
+	}
+}
 
 type Props = Record<string, any>;
 export interface SvelteComponentDev {
diff --git a/test/js/samples/capture-inject-state/expected.js b/test/js/samples/capture-inject-state/expected.js
index 8593145565..cd719ac5d2 100644
--- a/test/js/samples/capture-inject-state/expected.js
+++ b/test/js/samples/capture-inject-state/expected.js
@@ -14,6 +14,7 @@ import {
 	space,
 	subscribe,
 	text,
+	validate_slots,
 	validate_store
 } from "svelte/internal";
 
@@ -114,6 +115,9 @@ function instance($$self, $$props, $$invalidate) {
 		if (!~writable_props.indexOf(key) && key.slice(0, 2) !== "$$") console.warn(`<Component> was created with unknown prop '${key}'`);
 	});
 
+	let { $$slots = {}, $$scope } = $$props;
+	validate_slots("Component", $$slots, []);
+
 	$$self.$set = $$props => {
 		if ("prop" in $$props) $$subscribe_prop($$invalidate(0, prop = $$props.prop));
 		if ("alias" in $$props) $$invalidate(1, realName = $$props.alias);
diff --git a/test/js/samples/debug-empty/expected.js b/test/js/samples/debug-empty/expected.js
index 87d78bd698..dd142adb26 100644
--- a/test/js/samples/debug-empty/expected.js
+++ b/test/js/samples/debug-empty/expected.js
@@ -12,7 +12,8 @@ import {
 	safe_not_equal,
 	set_data_dev,
 	space,
-	text
+	text,
+	validate_slots
 } from "svelte/internal";
 
 const file = undefined;
@@ -75,6 +76,9 @@ function instance($$self, $$props, $$invalidate) {
 		if (!~writable_props.indexOf(key) && key.slice(0, 2) !== "$$") console.warn(`<Component> was created with unknown prop '${key}'`);
 	});
 
+	let { $$slots = {}, $$scope } = $$props;
+	validate_slots("Component", $$slots, []);
+
 	$$self.$set = $$props => {
 		if ("name" in $$props) $$invalidate(0, name = $$props.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 589c4a7832..977702b99f 100644
--- a/test/js/samples/debug-foo-bar-baz-things/expected.js
+++ b/test/js/samples/debug-foo-bar-baz-things/expected.js
@@ -14,7 +14,8 @@ import {
 	set_data_dev,
 	space,
 	text,
-	validate_each_argument
+	validate_each_argument,
+	validate_slots
 } from "svelte/internal";
 
 const file = undefined;
@@ -179,6 +180,9 @@ function instance($$self, $$props, $$invalidate) {
 		if (!~writable_props.indexOf(key) && key.slice(0, 2) !== "$$") console.warn(`<Component> was created with unknown prop '${key}'`);
 	});
 
+	let { $$slots = {}, $$scope } = $$props;
+	validate_slots("Component", $$slots, []);
+
 	$$self.$set = $$props => {
 		if ("things" in $$props) $$invalidate(0, things = $$props.things);
 		if ("foo" in $$props) $$invalidate(1, foo = $$props.foo);
diff --git a/test/js/samples/debug-foo/expected.js b/test/js/samples/debug-foo/expected.js
index 10129e1b28..fe62ff77bf 100644
--- a/test/js/samples/debug-foo/expected.js
+++ b/test/js/samples/debug-foo/expected.js
@@ -14,7 +14,8 @@ import {
 	set_data_dev,
 	space,
 	text,
-	validate_each_argument
+	validate_each_argument,
+	validate_slots
 } from "svelte/internal";
 
 const file = undefined;
@@ -171,6 +172,9 @@ function instance($$self, $$props, $$invalidate) {
 		if (!~writable_props.indexOf(key) && key.slice(0, 2) !== "$$") console.warn(`<Component> was created with unknown prop '${key}'`);
 	});
 
+	let { $$slots = {}, $$scope } = $$props;
+	validate_slots("Component", $$slots, []);
+
 	$$self.$set = $$props => {
 		if ("things" in $$props) $$invalidate(0, things = $$props.things);
 		if ("foo" in $$props) $$invalidate(1, foo = $$props.foo);
diff --git a/test/js/samples/debug-hoisted/expected.js b/test/js/samples/debug-hoisted/expected.js
index 190ff12c50..0e634297f0 100644
--- a/test/js/samples/debug-hoisted/expected.js
+++ b/test/js/samples/debug-hoisted/expected.js
@@ -4,7 +4,8 @@ import {
 	dispatch_dev,
 	init,
 	noop,
-	safe_not_equal
+	safe_not_equal,
+	validate_slots
 } from "svelte/internal";
 
 const file = undefined;
@@ -56,6 +57,8 @@ function instance($$self, $$props, $$invalidate) {
 		if (!~writable_props.indexOf(key) && key.slice(0, 2) !== "$$") console.warn(`<Component> was created with unknown prop '${key}'`);
 	});
 
+	let { $$slots = {}, $$scope } = $$props;
+	validate_slots("Component", $$slots, []);
 	$$self.$capture_state = () => ({ obj, kobzol });
 
 	$$self.$inject_state = $$props => {
diff --git a/test/js/samples/debug-no-dependencies/expected.js b/test/js/samples/debug-no-dependencies/expected.js
index a097869e74..76068e8cf4 100644
--- a/test/js/samples/debug-no-dependencies/expected.js
+++ b/test/js/samples/debug-no-dependencies/expected.js
@@ -11,7 +11,8 @@ import {
 	safe_not_equal,
 	space,
 	text,
-	validate_each_argument
+	validate_each_argument,
+	validate_slots
 } from "svelte/internal";
 
 const file = undefined;
@@ -141,6 +142,8 @@ function instance($$self, $$props) {
 		if (!~writable_props.indexOf(key) && key.slice(0, 2) !== "$$") console.warn(`<Component> was created with unknown prop '${key}'`);
 	});
 
+	let { $$slots = {}, $$scope } = $$props;
+	validate_slots("Component", $$slots, []);
 	return [];
 }
 
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 9c28e04064..0a50e2cd97 100644
--- a/test/js/samples/dev-warning-missing-data-computed/expected.js
+++ b/test/js/samples/dev-warning-missing-data-computed/expected.js
@@ -12,7 +12,8 @@ import {
 	safe_not_equal,
 	set_data_dev,
 	space,
-	text
+	text,
+	validate_slots
 } from "svelte/internal";
 
 const file = undefined;
@@ -72,6 +73,9 @@ function instance($$self, $$props, $$invalidate) {
 		if (!~writable_props.indexOf(key) && key.slice(0, 2) !== "$$") console.warn(`<Component> was created with unknown prop '${key}'`);
 	});
 
+	let { $$slots = {}, $$scope } = $$props;
+	validate_slots("Component", $$slots, []);
+
 	$$self.$set = $$props => {
 		if ("foo" in $$props) $$invalidate(0, foo = $$props.foo);
 	};
diff --git a/test/js/samples/loop-protect/expected.js b/test/js/samples/loop-protect/expected.js
index f433bd61a9..c52d9df437 100644
--- a/test/js/samples/loop-protect/expected.js
+++ b/test/js/samples/loop-protect/expected.js
@@ -11,7 +11,8 @@ import {
 	insert_dev,
 	loop_guard,
 	noop,
-	safe_not_equal
+	safe_not_equal,
+	validate_slots
 } from "svelte/internal";
 
 const { console: console_1 } = globals;
@@ -110,6 +111,9 @@ function instance($$self, $$props, $$invalidate) {
 		if (!~writable_props.indexOf(key) && key.slice(0, 2) !== "$$") console_1.warn(`<Component> was created with unknown prop '${key}'`);
 	});
 
+	let { $$slots = {}, $$scope } = $$props;
+	validate_slots("Component", $$slots, []);
+
 	function div_binding($$value) {
 		binding_callbacks[$$value ? "unshift" : "push"](() => {
 			$$invalidate(0, node = $$value);
@@ -161,4 +165,4 @@ class Component extends SvelteComponentDev {
 	}
 }
 
-export default Component;
+export default Component;
\ No newline at end of file
diff --git a/test/runtime/samples/component-slot-warning/Nested.svelte b/test/runtime/samples/component-slot-warning/Nested.svelte
new file mode 100644
index 0000000000..c6f086d96c
--- /dev/null
+++ b/test/runtime/samples/component-slot-warning/Nested.svelte
@@ -0,0 +1 @@
+<slot name="slot2"></slot>
\ No newline at end of file
diff --git a/test/runtime/samples/component-slot-warning/_config.js b/test/runtime/samples/component-slot-warning/_config.js
new file mode 100644
index 0000000000..6ffe624782
--- /dev/null
+++ b/test/runtime/samples/component-slot-warning/_config.js
@@ -0,0 +1,9 @@
+export default {
+	compileOptions: {
+		dev: true
+	},
+	warnings: [
+		'<Nested> received an unexpected slot "default".',
+		'<Nested> received an unexpected slot "slot1".'
+	]
+};
diff --git a/test/runtime/samples/component-slot-warning/main.svelte b/test/runtime/samples/component-slot-warning/main.svelte
new file mode 100644
index 0000000000..c29ef3e85b
--- /dev/null
+++ b/test/runtime/samples/component-slot-warning/main.svelte
@@ -0,0 +1,7 @@
+<script>
+	import Nested from "./Nested.svelte";
+</script>
+<Nested>
+	<input slot="slot1">
+	<input slot="slot2">
+</Nested>

From a8291227ce6ebf959749ae5d6f86b017a140d4af Mon Sep 17 00:00:00 2001
From: Conduitry <git@chor.date>
Date: Wed, 4 Mar 2020 20:28:19 -0500
Subject: [PATCH 12/23] fit bitmask overflow initial dirty value in 'if' blocks
 (#4507)

---
 CHANGELOG.md                                  |  1 +
 src/compiler/compile/render_dom/Renderer.ts   |  1 +
 .../compile/render_dom/wrappers/IfBlock.ts    | 20 +++++-
 .../wrappers/shared/get_slot_definition.ts    |  2 +-
 .../samples/bitmask-overflow-if/_config.js    | 24 +++++++
 .../samples/bitmask-overflow-if/main.svelte   | 62 +++++++++++++++++++
 6 files changed, 106 insertions(+), 4 deletions(-)
 create mode 100644 test/runtime/samples/bitmask-overflow-if/_config.js
 create mode 100644 test/runtime/samples/bitmask-overflow-if/main.svelte

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f39308e5ff..e58b9b6e06 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,7 @@
 * In `vars` array, correctly indicate whether `module` variables are `mutated` or `reassigned` ([#3215](https://github.com/sveltejs/svelte/issues/3215))
 * Fix spread props not updating in certain situations ([#3521](https://github.com/sveltejs/svelte/issues/3521), [#4480](https://github.com/sveltejs/svelte/issues/4480))
 * Use the fallback content for slots if they are passed only whitespace ([#4092](https://github.com/sveltejs/svelte/issues/4092))
+* Fix bitmask overflow for `{#if}` blocks ([#4263](https://github.com/sveltejs/svelte/issues/4263))
 * In `dev` mode, check for unknown props even if the component has no writable props ([#4323](https://github.com/sveltejs/svelte/issues/4323))
 * Exclude global variables from `$capture_state` ([#4463](https://github.com/sveltejs/svelte/issues/4463))
 * Fix bitmask overflow for slots ([#4481](https://github.com/sveltejs/svelte/issues/4481))
diff --git a/src/compiler/compile/render_dom/Renderer.ts b/src/compiler/compile/render_dom/Renderer.ts
index fbb0c76d7d..2501279214 100644
--- a/src/compiler/compile/render_dom/Renderer.ts
+++ b/src/compiler/compile/render_dom/Renderer.ts
@@ -230,6 +230,7 @@ export default class Renderer {
 			return bitmask;
 		};
 
+		// TODO: context-overflow make it less gross
 		return {
 			// Using a ParenthesizedExpression allows us to create
 			// the expression lazily. TODO would be better if
diff --git a/src/compiler/compile/render_dom/wrappers/IfBlock.ts b/src/compiler/compile/render_dom/wrappers/IfBlock.ts
index dfc2228bc5..0506c943f9 100644
--- a/src/compiler/compile/render_dom/wrappers/IfBlock.ts
+++ b/src/compiler/compile/render_dom/wrappers/IfBlock.ts
@@ -288,7 +288,7 @@ export default class IfBlockWrapper extends Wrapper {
 		}
 
 		block.chunks.init.push(b`
-			let ${current_block_type} = ${select_block_type}(#ctx, -1);
+			let ${current_block_type} = ${select_block_type}(#ctx, ${this.get_initial_dirty_bit()});
 			let ${name} = ${get_block};
 		`);
 
@@ -407,12 +407,12 @@ export default class IfBlockWrapper extends Wrapper {
 
 		if (has_else) {
 			block.chunks.init.push(b`
-				${current_block_type_index} = ${select_block_type}(#ctx, -1);
+				${current_block_type_index} = ${select_block_type}(#ctx, ${this.get_initial_dirty_bit()});
 				${name} = ${if_blocks}[${current_block_type_index}] = ${if_block_creators}[${current_block_type_index}](#ctx);
 			`);
 		} else {
 			block.chunks.init.push(b`
-				if (~(${current_block_type_index} = ${select_block_type}(#ctx, -1))) {
+				if (~(${current_block_type_index} = ${select_block_type}(#ctx, ${this.get_initial_dirty_bit()}))) {
 					${name} = ${if_blocks}[${current_block_type_index}] = ${if_block_creators}[${current_block_type_index}](#ctx);
 				}
 			`);
@@ -587,4 +587,18 @@ export default class IfBlockWrapper extends Wrapper {
 			`);
 		}
 	}
+
+	get_initial_dirty_bit() {
+		const _this = this;
+		// TODO: context-overflow make it less gross
+
+		const val = x`-1`;
+		return {
+			...val,
+			elements: [val],
+			get type() {
+				return _this.renderer.context_overflow ? 'ArrayExpression' : 'UnaryExpression';
+			},
+		};
+	}
 }
diff --git a/src/compiler/compile/render_dom/wrappers/shared/get_slot_definition.ts b/src/compiler/compile/render_dom/wrappers/shared/get_slot_definition.ts
index 9ab48dd035..0f28689df3 100644
--- a/src/compiler/compile/render_dom/wrappers/shared/get_slot_definition.ts
+++ b/src/compiler/compile/render_dom/wrappers/shared/get_slot_definition.ts
@@ -63,7 +63,7 @@ export function get_slot_definition(block: Block, scope: TemplateScope, lets: Le
 	const { context_lookup } = block.renderer;
 
 	// i am well aware that this code is gross
-	// TODO make it less gross
+	// TODO: context-overflow make it less gross
 	const changes = {
 		type: 'ParenthesizedExpression',
 		get expression() {
diff --git a/test/runtime/samples/bitmask-overflow-if/_config.js b/test/runtime/samples/bitmask-overflow-if/_config.js
new file mode 100644
index 0000000000..74bc70d414
--- /dev/null
+++ b/test/runtime/samples/bitmask-overflow-if/_config.js
@@ -0,0 +1,24 @@
+export default {
+	html: `
+		012345678910111213141516171819202122232425262728293031323334353637383940
+		expected: true
+		if: true
+		<button></button>
+	`,
+
+	async test({ assert, component, target, window }) {
+		const button = target.querySelector("button");
+		await button.dispatchEvent(new window.MouseEvent("click"));
+
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			112345678910111213141516171819202122232425262728293031323334353637383940
+			expected: false
+			if: false
+			<div></div>
+			<button></button>
+		`
+		);
+	}
+};
diff --git a/test/runtime/samples/bitmask-overflow-if/main.svelte b/test/runtime/samples/bitmask-overflow-if/main.svelte
new file mode 100644
index 0000000000..2c1c453091
--- /dev/null
+++ b/test/runtime/samples/bitmask-overflow-if/main.svelte
@@ -0,0 +1,62 @@
+<script>
+	import { fade } from 'svelte/transition';
+	export let _a = [];
+	export let _0 = '0';
+	export let _1 = '1';
+	export let _2 = '2';
+	export let _3 = '3';
+	export let _4 = '4';
+	export let _5 = '5';
+	export let _6 = '6';
+	export let _7 = '7';
+	export let _8 = '8';
+	export let _9 = '9';
+	export let _10 = '10';
+	export let _11 = '11';
+	export let _12 = '12';
+	export let _13 = '13';
+	export let _14 = '14';
+	export let _15 = '15';
+	export let _16 = '16';
+	export let _17 = '17';
+	export let _18 = '18';
+	export let _19 = '19';
+	export let _20 = '20';
+	export let _21 = '21';
+	export let _22 = '22';
+	export let _23 = '23';
+	export let _24 = '24';
+	export let _25 = '25';
+	export let _26 = '26';
+	export let _27 = '27';
+	export let _28 = '28';
+	export let _29 = '29';
+	export let _30 = '30';
+	export let _31 = '31';
+	export let _32 = '32';
+	export let _33 = '33';
+	export let _34 = '34';
+	export let _35 = '35';
+	export let _36 = '36';
+	export let _37 = '37';
+	export let _38 = '38';
+	export let _39 = '39';
+	export let _40 = '40';
+
+	function update() {
+		_0 = '1';
+	}
+</script>
+
+
+{_0}{_1}{_2}{_3}{_4}{_5}{_6}{_7}{_8}{_9}{_10}{_11}{_12}{_13}{_14}{_15}{_16}{_17}{_18}{_19}{_20}{_21}{_22}{_23}{_24}{_25}{_26}{_27}{_28}{_29}{_30}{_31}{_32}{_33}{_34}{_35}{_36}{_37}{_38}{_39}{_40}
+
+expected: {_a.indexOf(_0) && _0 === '0' && _1 === '1'}
+{#if _a.indexOf(_0) && _0 === '0' && _1 === '1'}
+if: true
+{:else}
+if: false
+<div out:fade></div>
+{/if}
+
+<button on:click={update}></button>
\ No newline at end of file

From 345d5f27ee2ed5fdd3f0bf2bea84c9f0f57b038e Mon Sep 17 00:00:00 2001
From: Tan Li Hau <lhtan93@gmail.com>
Date: Thu, 5 Mar 2020 10:12:30 +0800
Subject: [PATCH 13/23] fix lazy code breaks in build

---
 src/compiler/compile/render_dom/wrappers/IfBlock.ts | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/src/compiler/compile/render_dom/wrappers/IfBlock.ts b/src/compiler/compile/render_dom/wrappers/IfBlock.ts
index 0506c943f9..207e1e349e 100644
--- a/src/compiler/compile/render_dom/wrappers/IfBlock.ts
+++ b/src/compiler/compile/render_dom/wrappers/IfBlock.ts
@@ -9,7 +9,7 @@ import FragmentWrapper from './Fragment';
 import { b, x } from 'code-red';
 import { walk } from 'estree-walker';
 import { is_head } from './shared/is_head';
-import { Identifier, Node } from 'estree';
+import { Identifier, Node, UnaryExpression } from 'estree';
 
 function is_else_if(node: ElseBlock) {
 	return (
@@ -591,14 +591,17 @@ export default class IfBlockWrapper extends Wrapper {
 	get_initial_dirty_bit() {
 		const _this = this;
 		// TODO: context-overflow make it less gross
-
-		const val = x`-1`;
+		const val: UnaryExpression = x`-1` as UnaryExpression;
 		return {
-			...val,
-			elements: [val],
 			get type() {
 				return _this.renderer.context_overflow ? 'ArrayExpression' : 'UnaryExpression';
 			},
+			// as [-1]
+			elements: [val],
+			// as -1
+			operator: val.operator,
+			prefix: val.prefix,
+			argument: val.argument,
 		};
 	}
 }

From fd378f2d37463a1b9f3aba03a08c6693dea98d78 Mon Sep 17 00:00:00 2001
From: Conduitry <git@chor.date>
Date: Wed, 4 Mar 2020 21:31:38 -0500
Subject: [PATCH 14/23] -> v3.19.2

---
 CHANGELOG.md      | 2 +-
 package-lock.json | 2 +-
 package.json      | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index e58b9b6e06..f1564848b5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,6 @@
 # Svelte changelog
 
-## Unreleased
+## 3.19.2
 
 * In `dev` mode, display a runtime warning when a component is passed an unexpected slot ([#1020](https://github.com/sveltejs/svelte/issues/1020), [#1447](https://github.com/sveltejs/svelte/issues/1447))
 * In `vars` array, correctly indicate whether `module` variables are `mutated` or `reassigned` ([#3215](https://github.com/sveltejs/svelte/issues/3215))
diff --git a/package-lock.json b/package-lock.json
index f0f4e17422..014348f37e 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,6 +1,6 @@
 {
   "name": "svelte",
-  "version": "3.19.1",
+  "version": "3.19.2",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {
diff --git a/package.json b/package.json
index 7a02f1da10..009e5143a9 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "svelte",
-  "version": "3.19.1",
+  "version": "3.19.2",
   "description": "Cybernetically enhanced web apps",
   "module": "index.mjs",
   "main": "index",

From 48721520bdb9fa28f19e6940c67fd6e1f6396813 Mon Sep 17 00:00:00 2001
From: keke <zhoukekestar@163.com>
Date: Sun, 8 Mar 2020 21:36:11 +0800
Subject: [PATCH 15/23] docs: fix self-closing <svelte:options> tag (#4524)

---
 site/content/docs/03-run-time.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/site/content/docs/03-run-time.md b/site/content/docs/03-run-time.md
index c75ec694d9..0bbae24185 100644
--- a/site/content/docs/03-run-time.md
+++ b/site/content/docs/03-run-time.md
@@ -974,7 +974,7 @@ app.count += 1;
 Svelte components can also be compiled to custom elements (aka web components) using the `customElement: true` compiler option. You should specify a tag name for the component using the `<svelte:options>` [element](docs#svelte_options).
 
 ```html
-<svelte:options tag="my-element">
+<svelte:options tag="my-element" />
 
 <script>
 	export let name = 'world';

From 91d758e35b2b2154512ddd11e6b6d9d65708a99e Mon Sep 17 00:00:00 2001
From: Tan Li Hau <tanhauhau@users.noreply.github.com>
Date: Tue, 10 Mar 2020 10:22:39 +0800
Subject: [PATCH 16/23] introduce $$restProps (#4489)

---
 CHANGELOG.md                                  |  4 ++
 site/content/docs/02-template-syntax.md       |  9 +++
 src/compiler/compile/Component.ts             |  9 +--
 .../compile/nodes/shared/Expression.ts        |  5 +-
 src/compiler/compile/render_dom/Renderer.ts   |  9 ++-
 src/compiler/compile/render_dom/index.ts      | 26 +++++---
 src/compiler/compile/render_ssr/index.ts      |  5 ++
 .../compile/utils/reserved_keywords.ts        |  5 ++
 src/runtime/internal/utils.ts                 |  7 +++
 .../samples/$$rest-without-props/App.svelte   | 12 ++++
 .../samples/$$rest-without-props/_config.js   | 54 +++++++++++++++++
 .../samples/$$rest-without-props/main.svelte  | 25 ++++++++
 test/runtime/samples/$$rest/App.svelte        | 13 ++++
 test/runtime/samples/$$rest/_config.js        | 60 +++++++++++++++++++
 test/runtime/samples/$$rest/main.svelte       | 25 ++++++++
 .../Foo.svelte                                |  2 +-
 .../Foo.svelte                                |  7 +++
 .../_config.js                                |  7 +++
 .../main.svelte                               |  5 ++
 19 files changed, 272 insertions(+), 17 deletions(-)
 create mode 100644 src/compiler/compile/utils/reserved_keywords.ts
 create mode 100644 test/runtime/samples/$$rest-without-props/App.svelte
 create mode 100644 test/runtime/samples/$$rest-without-props/_config.js
 create mode 100644 test/runtime/samples/$$rest-without-props/main.svelte
 create mode 100644 test/runtime/samples/$$rest/App.svelte
 create mode 100644 test/runtime/samples/$$rest/_config.js
 create mode 100644 test/runtime/samples/$$rest/main.svelte
 create mode 100644 test/runtime/samples/dev-warning-unknown-props-with-$$rest/Foo.svelte
 create mode 100644 test/runtime/samples/dev-warning-unknown-props-with-$$rest/_config.js
 create mode 100644 test/runtime/samples/dev-warning-unknown-props-with-$$rest/main.svelte

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f1564848b5..7848af35be 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Svelte changelog
 
+## Unreleased
+
+* Expose object of unknown props in `$$restProps` ([#2930](https://github.com/sveltejs/svelte/issues/2930))
+
 ## 3.19.2
 
 * In `dev` mode, display a runtime warning when a component is passed an unexpected slot ([#1020](https://github.com/sveltejs/svelte/issues/1020), [#1447](https://github.com/sveltejs/svelte/issues/1447))
diff --git a/site/content/docs/02-template-syntax.md b/site/content/docs/02-template-syntax.md
index d25b348254..ea36474bed 100644
--- a/site/content/docs/02-template-syntax.md
+++ b/site/content/docs/02-template-syntax.md
@@ -113,6 +113,15 @@ An element or component can have multiple spread attributes, interspersed with r
 <Widget {...$$props}/>
 ```
 
+---
+
+*`$$restProps`* contains only the props which are *not* declared with `export`. It can be used to pass down other unknown attributes to an element in a component.
+
+```html
+<input {...$$restProps}>
+```
+
+---
 
 ### Text expressions
 
diff --git a/src/compiler/compile/Component.ts b/src/compiler/compile/Component.ts
index a7fe2992d1..ae2c4b704a 100644
--- a/src/compiler/compile/Component.ts
+++ b/src/compiler/compile/Component.ts
@@ -28,6 +28,7 @@ import { Node, ImportDeclaration, Identifier, Program, ExpressionStatement, Assi
 import add_to_set from './utils/add_to_set';
 import check_graph_for_cycles from './utils/check_graph_for_cycles';
 import { print, x, b } from 'code-red';
+import { is_reserved_keyword } from './utils/reserved_keywords';
 
 interface ComponentOptions {
 	namespace?: string;
@@ -185,7 +186,7 @@ export default class Component {
 
 		if (variable) {
 			variable.referenced = true;
-		} else if (name === '$$props') {
+		} else if (is_reserved_keyword(name)) {
 			this.add_var({
 				name,
 				injected: true,
@@ -649,7 +650,7 @@ export default class Component {
 					reassigned: true,
 					initialised: true,
 				});
-			} else if (name === '$$props') {
+			} else if (is_reserved_keyword(name)) {
 				this.add_var({
 					name,
 					injected: true,
@@ -1276,7 +1277,7 @@ export default class Component {
 
 	warn_if_undefined(name: string, node, template_scope: TemplateScope) {
 		if (name[0] === '$') {
-			if (name === '$' || name[1] === '$' && name !== '$$props') {
+			if (name === '$' || name[1] === '$' && !is_reserved_keyword(name)) {
 				this.error(node, {
 					code: 'illegal-global',
 					message: `${name} is an illegal variable name`
@@ -1285,7 +1286,7 @@ export default class Component {
 
 			this.has_reactive_assignments = true; // TODO does this belong here?
 
-			if (name === '$$props') return;
+			if (is_reserved_keyword(name)) return;
 
 			name = name.slice(1);
 		}
diff --git a/src/compiler/compile/nodes/shared/Expression.ts b/src/compiler/compile/nodes/shared/Expression.ts
index db0908c3f4..2f2541c720 100644
--- a/src/compiler/compile/nodes/shared/Expression.ts
+++ b/src/compiler/compile/nodes/shared/Expression.ts
@@ -13,6 +13,7 @@ import { b } from 'code-red';
 import { invalidate } from '../../render_dom/invalidate';
 import { Node, FunctionExpression, Identifier } from 'estree';
 import { TemplateNode } from '../../../interfaces';
+import { is_reserved_keyword } from '../../utils/reserved_keywords';
 
 type Owner = Wrapper | TemplateNode;
 
@@ -158,7 +159,7 @@ export default class Expression {
 	dynamic_dependencies() {
 		return Array.from(this.dependencies).filter(name => {
 			if (this.template_scope.is_let(name)) return true;
-			if (name === '$$props') return true;
+			if (is_reserved_keyword(name)) return true;
 
 			const variable = this.component.var_lookup.get(name);
 			return is_dynamic(variable);
@@ -355,7 +356,7 @@ function get_function_name(_node, parent) {
 }
 
 function is_contextual(component: Component, scope: TemplateScope, name: string) {
-	if (name === '$$props') return true;
+	if (is_reserved_keyword(name)) return true;
 
 	// if it's a name below root scope, it's contextual
 	if (!scope.is_top_level(name)) return true;
diff --git a/src/compiler/compile/render_dom/Renderer.ts b/src/compiler/compile/render_dom/Renderer.ts
index 2501279214..e933faf97a 100644
--- a/src/compiler/compile/render_dom/Renderer.ts
+++ b/src/compiler/compile/render_dom/Renderer.ts
@@ -5,6 +5,7 @@ import FragmentWrapper from './wrappers/Fragment';
 import { x } from 'code-red';
 import { Node, Identifier, MemberExpression, Literal, Expression, BinaryExpression } from 'estree';
 import flatten_reference from '../utils/flatten_reference';
+import { reserved_keywords } from '../utils/reserved_keywords';
 
 interface ContextMember {
 	name: string;
@@ -50,9 +51,11 @@ export default class Renderer {
 		// ensure store values are included in context
 		component.vars.filter(v => v.subscribable).forEach(v => this.add_to_context(`$${v.name}`));
 
-		if (component.var_lookup.has('$$props')) {
-			this.add_to_context('$$props');
-		}
+		reserved_keywords.forEach(keyword => {
+			if (component.var_lookup.has(keyword)) {
+				this.add_to_context(keyword);
+			}
+		});
 
 		if (component.slots.size > 0) {
 			this.add_to_context('$$scope');
diff --git a/src/compiler/compile/render_dom/index.ts b/src/compiler/compile/render_dom/index.ts
index fc3c94a2be..4009c6bddf 100644
--- a/src/compiler/compile/render_dom/index.ts
+++ b/src/compiler/compile/render_dom/index.ts
@@ -71,14 +71,24 @@ export default function dom(
 	}
 
 	const uses_props = component.var_lookup.has('$$props');
-	const $$props = uses_props ? `$$new_props` : `$$props`;
+	const uses_rest = component.var_lookup.has('$$restProps');
+	const $$props = uses_props || uses_rest ? `$$new_props` : `$$props`;
 	const props = component.vars.filter(variable => !variable.module && variable.export_name);
 	const writable_props = props.filter(variable => variable.writable);
 
-	const set = (uses_props || writable_props.length > 0 || component.slots.size > 0)
+	const omit_props_names = component.get_unique_name('omit_props_names');
+	const compute_rest = x`@compute_rest_props($$props, ${omit_props_names.name})`;
+	const rest = uses_rest ? b`
+		const ${omit_props_names.name} = [${props.map(prop => `"${prop.export_name}"`).join(',')}];
+		let $$restProps = ${compute_rest};
+	` : null;
+
+	const set = (uses_props || uses_rest || writable_props.length > 0 || component.slots.size > 0)
 		? x`
 			${$$props} => {
 				${uses_props && renderer.invalidate('$$props', x`$$props = @assign(@assign({}, $$props), @exclude_internal_props($$new_props))`)}
+				${uses_rest && !uses_props && x`$$props = @assign(@assign({}, $$props), @exclude_internal_props($$new_props))`}
+				${uses_rest && renderer.invalidate('$$restProps', x`$$restProps = ${compute_rest}`)}
 				${writable_props.map(prop =>
 					b`if ('${prop.export_name}' in ${$$props}) ${renderer.invalidate(prop.name, x`${prop.name} = ${$$props}.${prop.export_name}`)};`
 				)}
@@ -341,20 +351,20 @@ export default function dom(
 
 		component.reactive_declarations.forEach(d => {
 			const dependencies = Array.from(d.dependencies);
-			const uses_props = !!dependencies.find(n => n === '$$props');
+			const uses_rest_or_props = !!dependencies.find(n => n === '$$props' || n === '$$restProps');
 
 			const writable = dependencies.filter(n => {
 				const variable = component.var_lookup.get(n);
 				return variable && (variable.export_name || variable.mutated || variable.reassigned);
 			});
 
-			const condition = !uses_props && writable.length > 0 && renderer.dirty(writable, true);
+			const condition = !uses_rest_or_props && writable.length > 0 && renderer.dirty(writable, true);
 
 			let statement = d.node; // TODO remove label (use d.node.body) if it's not referenced
 
 			if (condition) statement = b`if (${condition}) { ${statement} }`[0] as Statement;
 
-			if (condition || uses_props) {
+			if (condition || uses_rest_or_props) {
 				reactive_declarations.push(statement);
 			} else {
 				fixed_reactive_declarations.push(statement);
@@ -383,7 +393,7 @@ export default function dom(
 		});
 
 		let unknown_props_check;
-		if (component.compile_options.dev && !component.var_lookup.has('$$props')) {
+		if (component.compile_options.dev && !(uses_props || uses_rest)) {
 			unknown_props_check = b`
 				const writable_props = [${writable_props.map(prop => x`'${prop.export_name}'`)}];
 				@_Object.keys($$props).forEach(key => {
@@ -402,6 +412,8 @@ export default function dom(
 
 		body.push(b`
 			function ${definition}(${args}) {
+				${rest}
+
 				${reactive_store_declarations}
 
 				${reactive_store_subscriptions}
@@ -473,7 +485,7 @@ export default function dom(
 							@insert(options.target, this, options.anchor);
 						}
 
-						${(props.length > 0 || uses_props) && b`
+						${(props.length > 0 || uses_props || uses_rest) && b`
 						if (options.props) {
 							this.$set(options.props);
 							@flush();
diff --git a/src/compiler/compile/render_ssr/index.ts b/src/compiler/compile/render_ssr/index.ts
index ad22869d32..c87fe3bdd9 100644
--- a/src/compiler/compile/render_ssr/index.ts
+++ b/src/compiler/compile/render_ssr/index.ts
@@ -31,6 +31,10 @@ export default function ssr(
 		{ code: null, map: null } :
 		component.stylesheet.render(options.filename, true);
 
+	const uses_rest = component.var_lookup.has('$$restProps');
+	const props = component.vars.filter(variable => !variable.module && variable.export_name);
+	const rest = uses_rest ? b`let $$restProps = @compute_rest_props($$props, [${props.map(prop => `"${prop.export_name}"`).join(',')}]);` : null;
+
 	const reactive_stores = component.vars.filter(variable => variable.name[0] === '$' && variable.name[1] !== '$');
 	const reactive_store_values = reactive_stores
 		.map(({ name }) => {
@@ -130,6 +134,7 @@ export default function ssr(
 			return ${literal};`;
 
 	const blocks = [
+		rest,
 		...reactive_stores.map(({ name }) => {
 			const store_name = name.slice(1);
 			const store = component.var_lookup.get(store_name);
diff --git a/src/compiler/compile/utils/reserved_keywords.ts b/src/compiler/compile/utils/reserved_keywords.ts
new file mode 100644
index 0000000000..75825c1719
--- /dev/null
+++ b/src/compiler/compile/utils/reserved_keywords.ts
@@ -0,0 +1,5 @@
+export const reserved_keywords = new Set(["$$props", "$$restProps"]);
+
+export function is_reserved_keyword(name) {
+	return reserved_keywords.has(name);
+}
\ No newline at end of file
diff --git a/src/runtime/internal/utils.ts b/src/runtime/internal/utils.ts
index acb88c7669..487116b655 100644
--- a/src/runtime/internal/utils.ts
+++ b/src/runtime/internal/utils.ts
@@ -109,6 +109,13 @@ export function exclude_internal_props(props) {
 	return result;
 }
 
+export function compute_rest_props(props, keys) {
+	const rest = {};
+	keys = new Set(keys);
+	for (const k in props) if (!keys.has(k) && k[0] !== '$') rest[k] = props[k];
+	return rest;
+}
+
 export function once(fn) {
 	let ran = false;
 	return function(this: any, ...args) {
diff --git a/test/runtime/samples/$$rest-without-props/App.svelte b/test/runtime/samples/$$rest-without-props/App.svelte
new file mode 100644
index 0000000000..e98fec30d4
--- /dev/null
+++ b/test/runtime/samples/$$rest-without-props/App.svelte
@@ -0,0 +1,12 @@
+<script>
+	export let a;
+	export function b() {}
+	export let c = 1;
+
+	$: length = Object.keys($$restProps).length;
+	$: values = Object.values($$restProps);
+</script>
+<div>Length: {length}</div>
+<div>Values: {values.join(',')}</div>
+
+<div {...$$restProps} />
\ No newline at end of file
diff --git a/test/runtime/samples/$$rest-without-props/_config.js b/test/runtime/samples/$$rest-without-props/_config.js
new file mode 100644
index 0000000000..017f9df561
--- /dev/null
+++ b/test/runtime/samples/$$rest-without-props/_config.js
@@ -0,0 +1,54 @@
+export default {
+	props: {
+		a: 3,
+		b: 4,
+		c: 5,
+		d: 6
+	},
+	html: `
+		<div>Length: 3</div>
+		<div>Values: 4,5,1</div>
+		<div d="4" e="5" foo="1"></div>
+		<button></button><button></button><button></button><button></button>
+	`,
+	async test({ assert, target, window, }) {
+		const [btn1, btn2, btn3, btn4] = target.querySelectorAll('button');
+		const clickEvent = new window.MouseEvent('click');
+
+		await btn1.dispatchEvent(clickEvent);
+		
+		assert.htmlEqual(target.innerHTML, `
+			<div>Length: 3</div>
+			<div>Values: 4,5,1</div>
+			<div d="4" e="5" foo="1"></div>
+			<button></button><button></button><button></button><button></button>
+		`);
+
+		await btn2.dispatchEvent(clickEvent);
+		
+		assert.htmlEqual(target.innerHTML, `
+			<div>Length: 3</div>
+			<div>Values: 34,5,1</div>
+			<div d="34" e="5" foo="1"></div>
+			<button></button><button></button><button></button><button></button>
+		`);
+
+		await btn3.dispatchEvent(clickEvent);
+		
+		assert.htmlEqual(target.innerHTML, `
+			<div>Length: 3</div>
+			<div>Values: 34,5,31</div>
+			<div d="34" e="5" foo="31"></div>
+			<button></button><button></button><button></button><button></button>
+		`);
+
+		await btn4.dispatchEvent(clickEvent);
+		
+		assert.htmlEqual(target.innerHTML, `
+			<div>Length: 4</div>
+			<div>Values: 34,5,31,2</div>
+			<div d="34" e="5" foo="31" bar="2"></div>
+			<button></button><button></button><button></button><button></button>
+		`);
+	}
+};
diff --git a/test/runtime/samples/$$rest-without-props/main.svelte b/test/runtime/samples/$$rest-without-props/main.svelte
new file mode 100644
index 0000000000..21b2690584
--- /dev/null
+++ b/test/runtime/samples/$$rest-without-props/main.svelte
@@ -0,0 +1,25 @@
+<script>
+	import App from './App.svelte';
+	let a = 1, b = 2, c = 3, d = 4, e = 5;
+	let f = { foo: 1 };
+
+	function updateProps() {
+		a = 31;
+		b = 32;
+	}
+	function updateRest() {
+		d = 34;
+	}
+	function updateSpread() {
+		f.foo = 31;
+	}
+	function updateSpread2() {
+		f.bar = 2;
+	}
+</script>
+
+<App {a} {b} {c} {d} {e} {...f} />
+<button on:click={updateProps}></button>
+<button on:click={updateRest}></button>
+<button on:click={updateSpread}></button>
+<button on:click={updateSpread2}></button>
\ No newline at end of file
diff --git a/test/runtime/samples/$$rest/App.svelte b/test/runtime/samples/$$rest/App.svelte
new file mode 100644
index 0000000000..875372f670
--- /dev/null
+++ b/test/runtime/samples/$$rest/App.svelte
@@ -0,0 +1,13 @@
+<script>
+	export let a;
+	export function b() {}
+	export let c = 1;
+
+	$: length = Object.keys($$restProps).length;
+	$: values = Object.values($$restProps);
+</script>
+<div>Length: {length}</div>
+<div>Values: {values.join(',')}</div>
+
+<div {...$$restProps} />
+<div {...$$props} />
\ No newline at end of file
diff --git a/test/runtime/samples/$$rest/_config.js b/test/runtime/samples/$$rest/_config.js
new file mode 100644
index 0000000000..255927f354
--- /dev/null
+++ b/test/runtime/samples/$$rest/_config.js
@@ -0,0 +1,60 @@
+export default {
+	props: {
+		a: 3,
+		b: 4,
+		c: 5,
+		d: 6
+	},
+	html: `
+		<div>Length: 3</div>
+		<div>Values: 4,5,1</div>
+		<div d="4" e="5" foo="1"></div>
+		<div a="1" b="2" c="3" d="4" e="5" foo="1"></div>
+		<button></button><button></button><button></button><button></button>
+	`,
+
+	async test({ assert, target, window, }) {
+		const [btn1, btn2, btn3, btn4] = target.querySelectorAll('button');
+		const clickEvent = new window.MouseEvent('click');
+
+		await btn1.dispatchEvent(clickEvent);
+		
+		assert.htmlEqual(target.innerHTML, `
+			<div>Length: 3</div>
+			<div>Values: 4,5,1</div>
+			<div d="4" e="5" foo="1"></div>
+			<div a="31" b="32" c="3" d="4" e="5" foo="1"></div>
+			<button></button><button></button><button></button><button></button>
+		`);
+
+		await btn2.dispatchEvent(clickEvent);
+		
+		assert.htmlEqual(target.innerHTML, `
+			<div>Length: 3</div>
+			<div>Values: 34,5,1</div>
+			<div d="34" e="5" foo="1"></div>
+			<div a="31" b="32" c="3" d="34" e="5" foo="1"></div>
+			<button></button><button></button><button></button><button></button>
+		`);
+
+		await btn3.dispatchEvent(clickEvent);
+		
+		assert.htmlEqual(target.innerHTML, `
+			<div>Length: 3</div>
+			<div>Values: 34,5,31</div>
+			<div d="34" e="5" foo="31"></div>
+			<div a="31" b="32" c="3" d="34" e="5" foo="31"></div>
+			<button></button><button></button><button></button><button></button>
+		`);
+
+		await btn4.dispatchEvent(clickEvent);
+		
+		assert.htmlEqual(target.innerHTML, `
+			<div>Length: 4</div>
+			<div>Values: 34,5,31,2</div>
+			<div d="34" e="5" foo="31" bar="2"></div>
+			<div a="31" b="32" c="3" d="34" e="5" foo="31" bar="2"></div>
+			<button></button><button></button><button></button><button></button>
+		`);
+	}
+};
diff --git a/test/runtime/samples/$$rest/main.svelte b/test/runtime/samples/$$rest/main.svelte
new file mode 100644
index 0000000000..21b2690584
--- /dev/null
+++ b/test/runtime/samples/$$rest/main.svelte
@@ -0,0 +1,25 @@
+<script>
+	import App from './App.svelte';
+	let a = 1, b = 2, c = 3, d = 4, e = 5;
+	let f = { foo: 1 };
+
+	function updateProps() {
+		a = 31;
+		b = 32;
+	}
+	function updateRest() {
+		d = 34;
+	}
+	function updateSpread() {
+		f.foo = 31;
+	}
+	function updateSpread2() {
+		f.bar = 2;
+	}
+</script>
+
+<App {a} {b} {c} {d} {e} {...f} />
+<button on:click={updateProps}></button>
+<button on:click={updateRest}></button>
+<button on:click={updateSpread}></button>
+<button on:click={updateSpread2}></button>
\ No newline at end of file
diff --git a/test/runtime/samples/dev-warning-unknown-props-with-$$props/Foo.svelte b/test/runtime/samples/dev-warning-unknown-props-with-$$props/Foo.svelte
index 9e5c62339d..375b1a6a0a 100644
--- a/test/runtime/samples/dev-warning-unknown-props-with-$$props/Foo.svelte
+++ b/test/runtime/samples/dev-warning-unknown-props-with-$$props/Foo.svelte
@@ -4,4 +4,4 @@
 </script>
 
 <div>{foo}</div>
-<div>{JSON.stringify($$props)}</div>
+<div>{JSON.stringify($$restProps)}</div>
diff --git a/test/runtime/samples/dev-warning-unknown-props-with-$$rest/Foo.svelte b/test/runtime/samples/dev-warning-unknown-props-with-$$rest/Foo.svelte
new file mode 100644
index 0000000000..9e5c62339d
--- /dev/null
+++ b/test/runtime/samples/dev-warning-unknown-props-with-$$rest/Foo.svelte
@@ -0,0 +1,7 @@
+<script>
+	export let foo = undefined;
+
+</script>
+
+<div>{foo}</div>
+<div>{JSON.stringify($$props)}</div>
diff --git a/test/runtime/samples/dev-warning-unknown-props-with-$$rest/_config.js b/test/runtime/samples/dev-warning-unknown-props-with-$$rest/_config.js
new file mode 100644
index 0000000000..62ad08624d
--- /dev/null
+++ b/test/runtime/samples/dev-warning-unknown-props-with-$$rest/_config.js
@@ -0,0 +1,7 @@
+export default {
+	compileOptions: {
+		dev: true
+	},
+
+	warnings: []
+};
diff --git a/test/runtime/samples/dev-warning-unknown-props-with-$$rest/main.svelte b/test/runtime/samples/dev-warning-unknown-props-with-$$rest/main.svelte
new file mode 100644
index 0000000000..1566cf3e41
--- /dev/null
+++ b/test/runtime/samples/dev-warning-unknown-props-with-$$rest/main.svelte
@@ -0,0 +1,5 @@
+<script>
+	import Foo from './Foo.svelte';
+</script>
+
+<Foo fo="sho"/>

From a66437b3c15e735139f9afb2ec25e3e1c612cd82 Mon Sep 17 00:00:00 2001
From: Tan Li Hau <tanhauhau@users.noreply.github.com>
Date: Thu, 12 Mar 2020 19:51:59 +0800
Subject: [PATCH 17/23] allow <svelte:self> to be part of a slot (#4532)

---
 CHANGELOG.md                                           |  1 +
 src/compiler/parse/state/tag.ts                        |  4 ++--
 test/parser/samples/error-self-reference/error.json    |  2 +-
 .../samples/self-reference-component/Countdown.svelte  |  7 +++++++
 .../samples/self-reference-component/_config.js        |  3 +++
 .../samples/self-reference-component/main.svelte       | 10 ++++++++++
 6 files changed, 24 insertions(+), 3 deletions(-)
 create mode 100644 test/runtime/samples/self-reference-component/Countdown.svelte
 create mode 100644 test/runtime/samples/self-reference-component/_config.js
 create mode 100644 test/runtime/samples/self-reference-component/main.svelte

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7848af35be..451fc58ca6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,7 @@
 
 ## Unreleased
 
+* Allow `<svelte:self>` to be used in a slot ([#2798](https://github.com/sveltejs/svelte/issues/2798))
 * Expose object of unknown props in `$$restProps` ([#2930](https://github.com/sveltejs/svelte/issues/2930))
 
 ## 3.19.2
diff --git a/src/compiler/parse/state/tag.ts b/src/compiler/parse/state/tag.ts
index 40bb01de9b..ce8a0a9aa7 100644
--- a/src/compiler/parse/state/tag.ts
+++ b/src/compiler/parse/state/tag.ts
@@ -241,7 +241,7 @@ function read_tag_name(parser: Parser) {
 
 		while (i--) {
 			const fragment = parser.stack[i];
-			if (fragment.type === 'IfBlock' || fragment.type === 'EachBlock') {
+			if (fragment.type === 'IfBlock' || fragment.type === 'EachBlock' || fragment.type === 'InlineComponent') {
 				legal = true;
 				break;
 			}
@@ -250,7 +250,7 @@ function read_tag_name(parser: Parser) {
 		if (!legal) {
 			parser.error({
 				code: `invalid-self-placement`,
-				message: `<svelte:self> components can only exist inside if-blocks or each-blocks`
+				message: `<svelte:self> components can only exist inside {#if} blocks, {#each} blocks, or slots passed to components`
 			}, start);
 		}
 
diff --git a/test/parser/samples/error-self-reference/error.json b/test/parser/samples/error-self-reference/error.json
index 798b5cb300..31ecab2b12 100644
--- a/test/parser/samples/error-self-reference/error.json
+++ b/test/parser/samples/error-self-reference/error.json
@@ -1,6 +1,6 @@
 {
 	"code": "invalid-self-placement",
-	"message": "<svelte:self> components can only exist inside if-blocks or each-blocks",
+	"message": "<svelte:self> components can only exist inside {#if} blocks, {#each} blocks, or slots passed to components",
 	"start": {
 		"line": 1,
 		"column": 1,
diff --git a/test/runtime/samples/self-reference-component/Countdown.svelte b/test/runtime/samples/self-reference-component/Countdown.svelte
new file mode 100644
index 0000000000..21178f2567
--- /dev/null
+++ b/test/runtime/samples/self-reference-component/Countdown.svelte
@@ -0,0 +1,7 @@
+<script>
+	export let count;
+</script>
+
+{#if count > 0}
+	<slot count={count-1}></slot>
+{/if}
\ No newline at end of file
diff --git a/test/runtime/samples/self-reference-component/_config.js b/test/runtime/samples/self-reference-component/_config.js
new file mode 100644
index 0000000000..e3e0ad3a4f
--- /dev/null
+++ b/test/runtime/samples/self-reference-component/_config.js
@@ -0,0 +1,3 @@
+export default {
+	html: '5 4 3 2 1 0',
+};
\ No newline at end of file
diff --git a/test/runtime/samples/self-reference-component/main.svelte b/test/runtime/samples/self-reference-component/main.svelte
new file mode 100644
index 0000000000..fd28ec4e40
--- /dev/null
+++ b/test/runtime/samples/self-reference-component/main.svelte
@@ -0,0 +1,10 @@
+<script>
+	import Countdown from './Countdown.svelte';
+	export let count = 5;
+</script>
+
+{count}
+
+<Countdown {count} let:count={i}>
+	<svelte:self count={i} />
+</Countdown>
\ No newline at end of file

From ec3589e31425c54cda3c5f6a80b89eb3aaa7bd52 Mon Sep 17 00:00:00 2001
From: Tan Li Hau <tanhauhau@users.noreply.github.com>
Date: Sun, 15 Mar 2020 02:15:24 +0800
Subject: [PATCH 18/23] fix hydration of top-level content (#4550)

---
 CHANGELOG.md                                            | 1 +
 src/runtime/internal/Component.ts                       | 6 ++++--
 test/hydration/samples/top-level-cleanup-2/_after.html  | 1 +
 test/hydration/samples/top-level-cleanup-2/_before.html | 2 ++
 test/hydration/samples/top-level-cleanup-2/_config.js   | 1 +
 test/hydration/samples/top-level-cleanup-2/main.svelte  | 1 +
 test/hydration/samples/top-level-cleanup/_after.html    | 1 +
 test/hydration/samples/top-level-cleanup/_before.html   | 1 +
 test/hydration/samples/top-level-cleanup/_config.js     | 1 +
 test/hydration/samples/top-level-cleanup/main.svelte    | 1 +
 10 files changed, 14 insertions(+), 2 deletions(-)
 create mode 100644 test/hydration/samples/top-level-cleanup-2/_after.html
 create mode 100644 test/hydration/samples/top-level-cleanup-2/_before.html
 create mode 100644 test/hydration/samples/top-level-cleanup-2/_config.js
 create mode 100644 test/hydration/samples/top-level-cleanup-2/main.svelte
 create mode 100644 test/hydration/samples/top-level-cleanup/_after.html
 create mode 100644 test/hydration/samples/top-level-cleanup/_before.html
 create mode 100644 test/hydration/samples/top-level-cleanup/_config.js
 create mode 100644 test/hydration/samples/top-level-cleanup/main.svelte

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 451fc58ca6..084a900295 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,7 @@
 
 * Allow `<svelte:self>` to be used in a slot ([#2798](https://github.com/sveltejs/svelte/issues/2798))
 * Expose object of unknown props in `$$restProps` ([#2930](https://github.com/sveltejs/svelte/issues/2930))
+* Fix hydration of top-level content ([#4542](https://github.com/sveltejs/svelte/issues/4542))
 
 ## 3.19.2
 
diff --git a/src/runtime/internal/Component.ts b/src/runtime/internal/Component.ts
index 10588a0804..7d2a92fa1b 100644
--- a/src/runtime/internal/Component.ts
+++ b/src/runtime/internal/Component.ts
@@ -1,7 +1,7 @@
 import { add_render_callback, flush, schedule_update, dirty_components } from './scheduler';
 import { current_component, set_current_component } from './lifecycle';
 import { blank_object, is_function, run, run_all, noop } from './utils';
-import { children } from './dom';
+import { children, detach } from './dom';
 import { transition_in } from './transitions';
 
 interface Fragment {
@@ -146,8 +146,10 @@ export function init(component, options, instance, create_fragment, not_equal, p
 
 	if (options.target) {
 		if (options.hydrate) {
+			const nodes = children(options.target);
 			// eslint-disable-next-line @typescript-eslint/no-non-null-assertion
-			$$.fragment && $$.fragment!.l(children(options.target));
+			$$.fragment && $$.fragment!.l(nodes);
+			nodes.forEach(detach);
 		} else {
 			// eslint-disable-next-line @typescript-eslint/no-non-null-assertion
 			$$.fragment && $$.fragment!.c();
diff --git a/test/hydration/samples/top-level-cleanup-2/_after.html b/test/hydration/samples/top-level-cleanup-2/_after.html
new file mode 100644
index 0000000000..8dca56dd88
--- /dev/null
+++ b/test/hydration/samples/top-level-cleanup-2/_after.html
@@ -0,0 +1 @@
+<div>Hello world</div>
\ No newline at end of file
diff --git a/test/hydration/samples/top-level-cleanup-2/_before.html b/test/hydration/samples/top-level-cleanup-2/_before.html
new file mode 100644
index 0000000000..fdc2379f63
--- /dev/null
+++ b/test/hydration/samples/top-level-cleanup-2/_before.html
@@ -0,0 +1,2 @@
+<main>This should be thrown away</main>
+<div>hello</div>
\ No newline at end of file
diff --git a/test/hydration/samples/top-level-cleanup-2/_config.js b/test/hydration/samples/top-level-cleanup-2/_config.js
new file mode 100644
index 0000000000..ff8b4c5632
--- /dev/null
+++ b/test/hydration/samples/top-level-cleanup-2/_config.js
@@ -0,0 +1 @@
+export default {};
diff --git a/test/hydration/samples/top-level-cleanup-2/main.svelte b/test/hydration/samples/top-level-cleanup-2/main.svelte
new file mode 100644
index 0000000000..8dca56dd88
--- /dev/null
+++ b/test/hydration/samples/top-level-cleanup-2/main.svelte
@@ -0,0 +1 @@
+<div>Hello world</div>
\ No newline at end of file
diff --git a/test/hydration/samples/top-level-cleanup/_after.html b/test/hydration/samples/top-level-cleanup/_after.html
new file mode 100644
index 0000000000..8dca56dd88
--- /dev/null
+++ b/test/hydration/samples/top-level-cleanup/_after.html
@@ -0,0 +1 @@
+<div>Hello world</div>
\ No newline at end of file
diff --git a/test/hydration/samples/top-level-cleanup/_before.html b/test/hydration/samples/top-level-cleanup/_before.html
new file mode 100644
index 0000000000..c7e4bba233
--- /dev/null
+++ b/test/hydration/samples/top-level-cleanup/_before.html
@@ -0,0 +1 @@
+<main>This should be thrown away</main>
\ No newline at end of file
diff --git a/test/hydration/samples/top-level-cleanup/_config.js b/test/hydration/samples/top-level-cleanup/_config.js
new file mode 100644
index 0000000000..ff8b4c5632
--- /dev/null
+++ b/test/hydration/samples/top-level-cleanup/_config.js
@@ -0,0 +1 @@
+export default {};
diff --git a/test/hydration/samples/top-level-cleanup/main.svelte b/test/hydration/samples/top-level-cleanup/main.svelte
new file mode 100644
index 0000000000..8dca56dd88
--- /dev/null
+++ b/test/hydration/samples/top-level-cleanup/main.svelte
@@ -0,0 +1 @@
+<div>Hello world</div>
\ No newline at end of file

From 404ed3dbfe84e2d16c2a3658257536e194c33463 Mon Sep 17 00:00:00 2001
From: Tan Li Hau <tanhauhau@users.noreply.github.com>
Date: Sun, 15 Mar 2020 02:27:39 +0800
Subject: [PATCH 19/23] fix else-block update in keyed each-block (#4558)

Co-authored-by: Benjamin W. Broersma <bw@broersma.com>
---
 CHANGELOG.md                                  |  1 +
 .../compile/render_dom/wrappers/EachBlock.ts  | 60 +++++++++----------
 .../samples/each-block-keyed-else/_config.js  | 37 ++++++++++++
 .../samples/each-block-keyed-else/main.svelte | 12 ++++
 .../each-block-unkeyed-else-2/_config.js      | 37 ++++++++++++
 .../each-block-unkeyed-else-2/main.svelte     | 12 ++++
 6 files changed, 129 insertions(+), 30 deletions(-)
 create mode 100644 test/runtime/samples/each-block-keyed-else/_config.js
 create mode 100644 test/runtime/samples/each-block-keyed-else/main.svelte
 create mode 100644 test/runtime/samples/each-block-unkeyed-else-2/_config.js
 create mode 100644 test/runtime/samples/each-block-unkeyed-else-2/main.svelte

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 084a900295..1e9024c318 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,7 @@
 
 * Allow `<svelte:self>` to be used in a slot ([#2798](https://github.com/sveltejs/svelte/issues/2798))
 * Expose object of unknown props in `$$restProps` ([#2930](https://github.com/sveltejs/svelte/issues/2930))
+* Fix updating keyed `{#each}` blocks with `{:else}` ([#4536](https://github.com/sveltejs/svelte/issues/4536), [#4549](https://github.com/sveltejs/svelte/issues/4549))
 * Fix hydration of top-level content ([#4542](https://github.com/sveltejs/svelte/issues/4542))
 
 ## 3.19.2
diff --git a/src/compiler/compile/render_dom/wrappers/EachBlock.ts b/src/compiler/compile/render_dom/wrappers/EachBlock.ts
index f0dfa5fbcc..43a0f754f9 100644
--- a/src/compiler/compile/render_dom/wrappers/EachBlock.ts
+++ b/src/compiler/compile/render_dom/wrappers/EachBlock.ts
@@ -62,6 +62,8 @@ export default class EachBlockWrapper extends Wrapper {
 
 	context_props: Array<Node | Node[]>;
 	index_name: Identifier;
+	updates: Array<Node | Node[]> = [];
+	dependencies: Set<string>;
 
 	var: Identifier = { type: 'Identifier', name: 'each' };
 
@@ -235,6 +237,12 @@ export default class EachBlockWrapper extends Wrapper {
 			update_mount_node
 		};
 
+		const all_dependencies = new Set(this.block.dependencies); // TODO should be dynamic deps only
+		this.node.expression.dynamic_dependencies().forEach((dependency: string) => {
+			all_dependencies.add(dependency);
+		});
+		this.dependencies = all_dependencies;
+
 		if (this.node.key) {
 			this.render_keyed(args);
 		} else {
@@ -291,7 +299,7 @@ export default class EachBlockWrapper extends Wrapper {
 			`);
 
 			if (this.else.block.has_update_method) {
-				block.chunks.update.push(b`
+				this.updates.push(b`
 					if (!${this.vars.data_length} && ${each_block_else}) {
 						${each_block_else}.p(#ctx, #dirty);
 					} else if (!${this.vars.data_length}) {
@@ -304,7 +312,7 @@ export default class EachBlockWrapper extends Wrapper {
 					}
 				`);
 			} else {
-				block.chunks.update.push(b`
+				this.updates.push(b`
 					if (${this.vars.data_length}) {
 						if (${each_block_else}) {
 							${each_block_else}.d(1);
@@ -323,6 +331,14 @@ export default class EachBlockWrapper extends Wrapper {
 			`);
 		}
 
+		if (this.updates.length) {
+			block.chunks.update.push(b`
+				if (${block.renderer.dirty(Array.from(all_dependencies))}) {
+					${this.updates}
+				}
+			`);
+		}
+
 		this.fragment.render(this.block, null, x`#nodes` as Identifier);
 
 		if (this.else) {
@@ -415,24 +431,17 @@ export default class EachBlockWrapper extends Wrapper {
 				? `@outro_and_destroy_block`
 				: `@destroy_block`;
 
-		const all_dependencies = new Set(this.block.dependencies); // TODO should be dynamic deps only
-		this.node.expression.dynamic_dependencies().forEach((dependency: string) => {
-			all_dependencies.add(dependency);
-		});
+		if (this.dependencies.size) {
+			this.updates.push(b`
+				const ${this.vars.each_block_value} = ${snippet};
+				${this.renderer.options.dev && b`@validate_each_argument(${this.vars.each_block_value});`}
 
-		if (all_dependencies.size) {
-			block.chunks.update.push(b`
-				if (${block.renderer.dirty(Array.from(all_dependencies))}) {
-					const ${this.vars.each_block_value} = ${snippet};
-					${this.renderer.options.dev && b`@validate_each_argument(${this.vars.each_block_value});`}
-
-					${this.block.has_outros && b`@group_outros();`}
-					${this.node.has_animation && b`for (let #i = 0; #i < ${view_length}; #i += 1) ${iterations}[#i].r();`}
-					${this.renderer.options.dev && b`@validate_each_keys(#ctx, ${this.vars.each_block_value}, ${this.vars.get_each_context}, ${get_key});`}
-					${iterations} = @update_keyed_each(${iterations}, #dirty, ${get_key}, ${dynamic ? 1 : 0}, #ctx, ${this.vars.each_block_value}, ${lookup}, ${update_mount_node}, ${destroy}, ${create_each_block}, ${update_anchor_node}, ${this.vars.get_each_context});
-					${this.node.has_animation && b`for (let #i = 0; #i < ${view_length}; #i += 1) ${iterations}[#i].a();`}
-					${this.block.has_outros && b`@check_outros();`}
-				}
+				${this.block.has_outros && b`@group_outros();`}
+				${this.node.has_animation && b`for (let #i = 0; #i < ${view_length}; #i += 1) ${iterations}[#i].r();`}
+				${this.renderer.options.dev && b`@validate_each_keys(#ctx, ${this.vars.each_block_value}, ${this.vars.get_each_context}, ${get_key});`}
+				${iterations} = @update_keyed_each(${iterations}, #dirty, ${get_key}, ${dynamic ? 1 : 0}, #ctx, ${this.vars.each_block_value}, ${lookup}, ${update_mount_node}, ${destroy}, ${create_each_block}, ${update_anchor_node}, ${this.vars.get_each_context});
+				${this.node.has_animation && b`for (let #i = 0; #i < ${view_length}; #i += 1) ${iterations}[#i].a();`}
+				${this.block.has_outros && b`@check_outros();`}
 			`);
 		}
 
@@ -504,12 +513,7 @@ export default class EachBlockWrapper extends Wrapper {
 			}
 		`);
 
-		const all_dependencies = new Set(this.block.dependencies); // TODO should be dynamic deps only
-		this.node.expression.dynamic_dependencies().forEach((dependency: string) => {
-			all_dependencies.add(dependency);
-		});
-
-		if (all_dependencies.size) {
+		if (this.dependencies.size) {
 			const has_transitions = !!(this.block.has_intro_method || this.block.has_outro_method);
 
 			const for_loop_body = this.block.has_update_method
@@ -588,11 +592,7 @@ export default class EachBlockWrapper extends Wrapper {
 				${remove_old_blocks}
 			`;
 
-			block.chunks.update.push(b`
-				if (${block.renderer.dirty(Array.from(all_dependencies))}) {
-					${update}
-				}
-			`);
+			this.updates.push(update);
 		}
 
 		if (this.block.has_outros) {
diff --git a/test/runtime/samples/each-block-keyed-else/_config.js b/test/runtime/samples/each-block-keyed-else/_config.js
new file mode 100644
index 0000000000..a5bf722a80
--- /dev/null
+++ b/test/runtime/samples/each-block-keyed-else/_config.js
@@ -0,0 +1,37 @@
+export default {
+	props: {
+		animals: ['alpaca', 'baboon', 'capybara'],
+		foo: 'something else'
+	},
+
+	html: `
+		before
+		<p>alpaca</p>
+		<p>baboon</p>
+		<p>capybara</p>
+		after
+	`,
+
+	test({ assert, component, target }) {
+		component.animals = [];
+		assert.htmlEqual(target.innerHTML, `
+			before
+			<p>no animals, but rather something else</p>
+			after
+		`);
+
+		component.foo = 'something other';
+		assert.htmlEqual(target.innerHTML, `
+			before
+			<p>no animals, but rather something other</p>
+			after
+		`);
+
+		component.animals = ['wombat'];
+		assert.htmlEqual(target.innerHTML, `
+			before
+			<p>wombat</p>
+			after
+		`);
+	}
+};
diff --git a/test/runtime/samples/each-block-keyed-else/main.svelte b/test/runtime/samples/each-block-keyed-else/main.svelte
new file mode 100644
index 0000000000..2a82653ff1
--- /dev/null
+++ b/test/runtime/samples/each-block-keyed-else/main.svelte
@@ -0,0 +1,12 @@
+<script>
+	export let animals;
+	export let foo;
+</script>
+
+before
+{#each animals as animal (animal)}
+	<p>{animal}</p>
+{:else}
+	<p>no animals, but rather {foo}</p>
+{/each}
+after
diff --git a/test/runtime/samples/each-block-unkeyed-else-2/_config.js b/test/runtime/samples/each-block-unkeyed-else-2/_config.js
new file mode 100644
index 0000000000..a5bf722a80
--- /dev/null
+++ b/test/runtime/samples/each-block-unkeyed-else-2/_config.js
@@ -0,0 +1,37 @@
+export default {
+	props: {
+		animals: ['alpaca', 'baboon', 'capybara'],
+		foo: 'something else'
+	},
+
+	html: `
+		before
+		<p>alpaca</p>
+		<p>baboon</p>
+		<p>capybara</p>
+		after
+	`,
+
+	test({ assert, component, target }) {
+		component.animals = [];
+		assert.htmlEqual(target.innerHTML, `
+			before
+			<p>no animals, but rather something else</p>
+			after
+		`);
+
+		component.foo = 'something other';
+		assert.htmlEqual(target.innerHTML, `
+			before
+			<p>no animals, but rather something other</p>
+			after
+		`);
+
+		component.animals = ['wombat'];
+		assert.htmlEqual(target.innerHTML, `
+			before
+			<p>wombat</p>
+			after
+		`);
+	}
+};
diff --git a/test/runtime/samples/each-block-unkeyed-else-2/main.svelte b/test/runtime/samples/each-block-unkeyed-else-2/main.svelte
new file mode 100644
index 0000000000..3275cb1f83
--- /dev/null
+++ b/test/runtime/samples/each-block-unkeyed-else-2/main.svelte
@@ -0,0 +1,12 @@
+<script>
+	export let animals;
+	export let foo;
+</script>
+
+before
+{#each animals as animal}
+	<p>{animal}</p>
+{:else}
+	<p>no animals, but rather {foo}</p>
+{/each}
+after

From ef791cc61644e013ea9bf8af4791d737b2241835 Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Sat, 14 Mar 2020 16:10:38 -0400
Subject: [PATCH 20/23] Bump acorn from 7.1.0 to 7.1.1 (#4553)

Bumps [acorn](https://github.com/acornjs/acorn) from 7.1.0 to 7.1.1.
- [Release notes](https://github.com/acornjs/acorn/releases)
- [Commits](https://github.com/acornjs/acorn/compare/7.1.0...7.1.1)

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
---
 package-lock.json | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/package-lock.json b/package-lock.json
index 014348f37e..858d90fd1b 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -280,9 +280,9 @@
       "dev": true
     },
     "acorn": {
-      "version": "7.1.0",
-      "resolved": "https://registry.npmjs.org/acorn/-/acorn-7.1.0.tgz",
-      "integrity": "sha512-kL5CuoXA/dgxlBbVrflsflzQ3PAas7RYZB52NOm/6839iVYJgKMJ3cQJD+t2i5+qFa8h3MDpEOJiS64E8JLnSQ==",
+      "version": "7.1.1",
+      "resolved": "https://registry.npmjs.org/acorn/-/acorn-7.1.1.tgz",
+      "integrity": "sha512-add7dgA5ppRPxCFJoAGfMDi7PIBXq1RtGo7BhbLaxwrXPOmw8gq48Y9ozT01hUKy9byMjlR20EJhu5zlkErEkg==",
       "dev": true
     },
     "acorn-globals": {

From 0ccdca21da697bed429e6fda7d57e1e6e02af970 Mon Sep 17 00:00:00 2001
From: "dependabot[bot]" <49699333+dependabot[bot]@users.noreply.github.com>
Date: Sat, 14 Mar 2020 16:10:57 -0400
Subject: [PATCH 21/23] Bump acorn from 7.0.0 to 7.1.1 in /site (#4554)

Bumps [acorn](https://github.com/acornjs/acorn) from 7.0.0 to 7.1.1.
- [Release notes](https://github.com/acornjs/acorn/releases)
- [Commits](https://github.com/acornjs/acorn/compare/7.0.0...7.1.1)

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
---
 site/package-lock.json | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/site/package-lock.json b/site/package-lock.json
index 646ca0ce53..5ce377c88c 100644
--- a/site/package-lock.json
+++ b/site/package-lock.json
@@ -1358,9 +1358,9 @@
       }
     },
     "acorn": {
-      "version": "7.0.0",
-      "resolved": "https://registry.npmjs.org/acorn/-/acorn-7.0.0.tgz",
-      "integrity": "sha512-PaF/MduxijYYt7unVGRuds1vBC9bFxbNf+VWqhOClfdgy7RlVkQqt610ig1/yxTgsDIfW1cWDel5EBbOy3jdtQ==",
+      "version": "7.1.1",
+      "resolved": "https://registry.npmjs.org/acorn/-/acorn-7.1.1.tgz",
+      "integrity": "sha512-add7dgA5ppRPxCFJoAGfMDi7PIBXq1RtGo7BhbLaxwrXPOmw8gq48Y9ozT01hUKy9byMjlR20EJhu5zlkErEkg==",
       "dev": true
     },
     "ansi-colors": {

From e06a900b2331e70f8b057dcbd36f6bd304f4c7dc Mon Sep 17 00:00:00 2001
From: vlasy <vlasy@users.noreply.github.com>
Date: Sat, 14 Mar 2020 21:15:37 +0100
Subject: [PATCH 22/23] throw compiler error when binding directly to const
 variables (#4506)

---
 src/compiler/compile/nodes/Binding.ts             |  5 +++++
 .../samples/binding-const-field/errors.json       |  1 +
 .../samples/binding-const-field/input.svelte      |  7 +++++++
 test/validator/samples/binding-const/errors.json  | 15 +++++++++++++++
 test/validator/samples/binding-const/input.svelte |  5 +++++
 5 files changed, 33 insertions(+)
 create mode 100644 test/validator/samples/binding-const-field/errors.json
 create mode 100644 test/validator/samples/binding-const-field/input.svelte
 create mode 100644 test/validator/samples/binding-const/errors.json
 create mode 100644 test/validator/samples/binding-const/input.svelte

diff --git a/src/compiler/compile/nodes/Binding.ts b/src/compiler/compile/nodes/Binding.ts
index 7d6fad0a81..2f199709c8 100644
--- a/src/compiler/compile/nodes/Binding.ts
+++ b/src/compiler/compile/nodes/Binding.ts
@@ -72,6 +72,11 @@ export default class Binding extends Node {
 			});
 
 			variable[this.expression.node.type === 'MemberExpression' ? 'mutated' : 'reassigned'] = true;
+
+			if (info.expression.type === 'Identifier' && !variable.writable) component.error(this.expression.node, {
+				code: 'invalid-binding',
+				message: 'Cannot bind to a variable which is not writable',
+			});
 		}
 
 		const type = parent.get_static_attribute_value('type');
diff --git a/test/validator/samples/binding-const-field/errors.json b/test/validator/samples/binding-const-field/errors.json
new file mode 100644
index 0000000000..fe51488c70
--- /dev/null
+++ b/test/validator/samples/binding-const-field/errors.json
@@ -0,0 +1 @@
+[]
diff --git a/test/validator/samples/binding-const-field/input.svelte b/test/validator/samples/binding-const-field/input.svelte
new file mode 100644
index 0000000000..055a16438d
--- /dev/null
+++ b/test/validator/samples/binding-const-field/input.svelte
@@ -0,0 +1,7 @@
+<script>
+	const dummy = {
+		foo: 'bar'
+	};
+</script>
+
+<input bind:value={dummy.foo}>
diff --git a/test/validator/samples/binding-const/errors.json b/test/validator/samples/binding-const/errors.json
new file mode 100644
index 0000000000..6d48af9c4e
--- /dev/null
+++ b/test/validator/samples/binding-const/errors.json
@@ -0,0 +1,15 @@
+[{
+	"code": "invalid-binding",
+	"message": "Cannot bind to a variable which is not writable",
+	"pos": 61,
+	"start": {
+		"line": 5,
+		"column": 19,
+		"character": 61
+	},
+	"end": {
+		"line": 5,
+		"column": 24,
+		"character": 66
+	}
+}]
\ No newline at end of file
diff --git a/test/validator/samples/binding-const/input.svelte b/test/validator/samples/binding-const/input.svelte
new file mode 100644
index 0000000000..1857a1932c
--- /dev/null
+++ b/test/validator/samples/binding-const/input.svelte
@@ -0,0 +1,5 @@
+<script>
+	const dummy = 'foo';
+</script>
+
+<input bind:value={dummy}>

From c46b3727f11132cf765028522d97f3fedf91c051 Mon Sep 17 00:00:00 2001
From: Conduitry <git@chor.date>
Date: Sat, 14 Mar 2020 16:17:12 -0400
Subject: [PATCH 23/23] update changelog

---
 CHANGELOG.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1e9024c318..6b9d08ea2a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,7 @@
 
 * Allow `<svelte:self>` to be used in a slot ([#2798](https://github.com/sveltejs/svelte/issues/2798))
 * Expose object of unknown props in `$$restProps` ([#2930](https://github.com/sveltejs/svelte/issues/2930))
+* Disallow binding directly to `const` variables ([#4479](https://github.com/sveltejs/svelte/issues/4479))
 * Fix updating keyed `{#each}` blocks with `{:else}` ([#4536](https://github.com/sveltejs/svelte/issues/4536), [#4549](https://github.com/sveltejs/svelte/issues/4549))
 * Fix hydration of top-level content ([#4542](https://github.com/sveltejs/svelte/issues/4542))