WIP

Author: Rich-Harris

packages/svelte/src/compiler/phases/2-analyze/visitors/VariableDeclarator.js

@@ -19,7 +19,7 @@ export function VariableDeclarator(node, context) {
 	if (context.state.analysis.runes) {
 		const init = node.init;
 		const rune = get_rune(init, context.state.scope);
-		const paths = extract_paths(node.id, b.id('dummy'));
+		const { paths } = extract_paths(node.id, b.id('dummy'));
 
 		for (const path of paths) {
 			validate_identifier_name(context.state.scope.get(/** @type {Identifier} */ (path.node).name));

packages/svelte/src/compiler/phases/3-transform/client/visitors/EachBlock.js

@@ -234,7 +234,9 @@ export function EachBlock(node, context) {
 	} else if (node.context) {
 		const unwrapped = (flags & EACH_ITEM_REACTIVE) !== 0 ? b.call('$.get', item) : item;
 
-		for (const path of extract_paths(node.context, unwrapped)) {
+		const { paths } = extract_paths(node.context, unwrapped);
+
+		for (const path of paths) {
 			const name = /** @type {Identifier} */ (path.node).name;
 			const needs_derived = path.has_default_value; // to ensure that default value is only called once
 

packages/svelte/src/compiler/phases/3-transform/client/visitors/SnippetBlock.js

@@ -43,7 +43,7 @@ export function SnippetBlock(node, context) {
 		let arg_alias = `$$arg${i}`;
 		args.push(b.id(arg_alias));
 
-		const paths = extract_paths(argument, b.maybe_call(b.id(arg_alias)));
+		const { paths } = extract_paths(argument, b.maybe_call(b.id(arg_alias)));
 
 		for (const path of paths) {
 			const name = /** @type {Identifier} */ (path.node).name;

packages/svelte/src/compiler/phases/3-transform/client/visitors/VariableDeclaration.js

@@ -142,7 +142,7 @@ export function VariableDeclaration(node, context) {
 					);
 				} else {
 					const tmp = b.id(context.state.scope.generate('tmp'));
-					const paths = extract_paths(declarator.id, tmp);
+					const { paths } = extract_paths(declarator.id, tmp);
 					declarations.push(
 						b.declarator(tmp, value),
 						...paths.map((path) => {
@@ -183,7 +183,9 @@ export function VariableDeclaration(node, context) {
 						);
 					}
 
-					for (const path of extract_paths(declarator.id, rhs)) {
+					const { paths } = extract_paths(declarator.id, rhs);
+
+					for (const path of paths) {
 						declarations.push(
 							b.declarator(path.node, b.call('$.derived', b.thunk(path.expression)))
 						);
@@ -218,7 +220,7 @@ export function VariableDeclaration(node, context) {
 					// Turn export let into props. It's really really weird because export let { x: foo, z: [bar]} = ..
 					// means that foo and bar are the props (i.e. the leafs are the prop names), not x and z.
 					const tmp = b.id(context.state.scope.generate('tmp'));
-					const paths = extract_paths(declarator.id, tmp);
+					const { paths } = extract_paths(declarator.id, tmp);
 
 					declarations.push(
 						b.declarator(
@@ -298,7 +300,7 @@ function create_state_declarators(declarator, { scope, analysis }, value) {
 	}
 
 	const tmp = b.id(scope.generate('tmp'));
-	const paths = extract_paths(declarator.id, tmp);
+	const { paths } = extract_paths(declarator.id, tmp);
 	return [
 		b.declarator(tmp, value),
 		...paths.map((path) => {

packages/svelte/src/compiler/phases/3-transform/server/visitors/VariableDeclaration.js

@@ -121,7 +121,7 @@ export function VariableDeclaration(node, context) {
 					// Turn export let into props. It's really really weird because export let { x: foo, z: [bar]} = ..
 					// means that foo and bar are the props (i.e. the leafs are the prop names), not x and z.
 					const tmp = b.id(context.state.scope.generate('tmp'));
-					const paths = extract_paths(declarator.id, tmp);
+					const { paths } = extract_paths(declarator.id, tmp);
 					declarations.push(
 						b.declarator(
 							tmp,
@@ -189,7 +189,7 @@ function create_state_declarators(declarator, scope, value) {
 	}
 
 	const tmp = b.id(scope.generate('tmp'));
-	const paths = extract_paths(declarator.id, tmp);
+	const { paths } = extract_paths(declarator.id, tmp);
 	return [
 		b.declarator(tmp, value), // TODO inject declarator for opts, so we can use it below
 		...paths.map((path) => {

packages/svelte/src/compiler/phases/3-transform/shared/assignments.js

@@ -23,7 +23,9 @@ export function visit_assignment_expression(node, context, build_assignment) {
 
 		let changed = false;
 
-		const assignments = extract_paths(node.left, rhs).map((path) => {
+		const { paths } = extract_paths(node.left, rhs);
+
+		const assignments = paths.map((path) => {
 			const value = path.expression;
 
 			let assignment = build_assignment('=', path.node, value, context);

packages/svelte/src/compiler/utils/ast.js

@@ -237,10 +237,15 @@ export function extract_identifiers_from_destructuring(node, nodes = []) {
  * Extracts all destructured assignments from a pattern.
  * @param {ESTree.Node} param
  * @param {ESTree.Expression} initial
- * @returns {DestructuredAssignment[]}
+ * @returns {{ paths: DestructuredAssignment[] }}
  */
 export function extract_paths(param, initial) {
-	return _extract_paths([], param, initial, initial, false);
+	/** @type {DestructuredAssignment[]} */
+	const paths = [];
+
+	_extract_paths(paths, param, initial, initial, false);
+
+	return { paths };
 }
 
 /**