From dfcc5f682913a100c38d804be14c370bee3931b2 Mon Sep 17 00:00:00 2001
From: Jack Goodall <jack@datawrapper.de>
Date: Tue, 12 Aug 2025 21:58:33 +0200
Subject: [PATCH] use BindDirective metadata to mark a spread element instead
 of setting the SpreadElement as the expression

---
 .../compiler/phases/1-parse/state/element.js  | 34 ++++++------------
 .../2-analyze/visitors/BindDirective.js       | 14 ++------
 .../client/visitors/BindDirective.js          |  3 +-
 .../client/visitors/RegularElement.js         |  2 +-
 .../client/visitors/shared/component.js       |  7 ++--
 .../client/visitors/shared/utils.js           |  7 ++--
 .../server/visitors/shared/component.js       |  2 +-
 .../server/visitors/shared/element.js         |  5 ++-
 .../3-transform/shared/spread_bindings.js     | 10 +++---
 .../src/compiler/types/legacy-nodes.d.ts      |  5 +--
 .../svelte/src/compiler/types/template.d.ts   |  3 +-
 packages/svelte/src/internal/shared/errors.js | 36 +++++++++----------
 packages/svelte/types/index.d.ts              |  4 +--
 13 files changed, 56 insertions(+), 76 deletions(-)

diff --git a/packages/svelte/src/compiler/phases/1-parse/state/element.js b/packages/svelte/src/compiler/phases/1-parse/state/element.js
index 731f4b5997..68db2c9df1 100644
--- a/packages/svelte/src/compiler/phases/1-parse/state/element.js
+++ b/packages/svelte/src/compiler/phases/1-parse/state/element.js
@@ -1,4 +1,4 @@
-/** @import { Expression, SpreadElement } from 'estree' */
+/** @import { Expression } from 'estree' */
 /** @import { AST } from '#compiler' */
 /** @import { Parser } from '../index.js' */
 import { is_void } from '../../../../utils.js';
@@ -618,15 +618,6 @@ function read_attribute(parser) {
 			e.directive_missing_name({ start, end: start + colon_index + 1 }, name);
 		}
 
-		if (
-			type !== 'BindDirective' &&
-			value !== true &&
-			'metadata' in value &&
-			value.metadata.expression.has_spread
-		) {
-			e.directive_invalid_value(value.start);
-		}
-
 		if (type === 'StyleDirective') {
 			return {
 				start,
@@ -643,7 +634,7 @@ function read_attribute(parser) {
 
 		const first_value = value === true ? undefined : Array.isArray(value) ? value[0] : value;
 
-		/** @type {Expression | SpreadElement | null} */
+		/** @type {Expression | null} */
 		let expression = null;
 
 		if (first_value) {
@@ -655,29 +646,26 @@ function read_attribute(parser) {
 				// TODO throw a parser error in a future version here if this `[ExpressionTag]` instead of `ExpressionTag`,
 				// which means stringified value, which isn't allowed for some directives?
 				expression = first_value.expression;
-
-				if (type === 'BindDirective' && first_value.metadata.expression.has_spread) {
-					expression = {
-						type: 'SpreadElement',
-						start: first_value.start,
-						end: first_value.end,
-						argument: expression
-					};
-				}
 			}
 		}
 
-		/** @type {AST.Directive} */
-		const directive = {
+		const directive = /** @type {AST.Directive} */ ({
 			start,
 			end,
 			type,
 			name: directive_name,
+			modifiers: [],
 			expression,
 			metadata: {
 				expression: create_expression_metadata()
 			}
-		};
+		});
+		if (first_value?.metadata.expression.has_spread) {
+			if (directive.type !== 'BindDirective') {
+				e.directive_invalid_value(first_value.start);
+			}
+			directive.metadata.spread_binding = true;
+		}
 
 		// @ts-expect-error we do this separately from the declaration to avoid upsetting typescript
 		directive.modifiers = modifiers;
diff --git a/packages/svelte/src/compiler/phases/2-analyze/visitors/BindDirective.js b/packages/svelte/src/compiler/phases/2-analyze/visitors/BindDirective.js
index a4aa13ad67..a562a0d46d 100644
--- a/packages/svelte/src/compiler/phases/2-analyze/visitors/BindDirective.js
+++ b/packages/svelte/src/compiler/phases/2-analyze/visitors/BindDirective.js
@@ -158,20 +158,11 @@ export function BindDirective(node, context) {
 		return;
 	}
 
-	if (node.expression.type === 'SpreadElement') {
+	if (node.metadata.spread_binding) {
 		if (node.name === 'group') {
 			e.bind_group_invalid_expression(node);
 		}
 
-		const argument = node.expression.argument;
-		if (
-			argument.type !== 'Identifier' &&
-			argument.type !== 'MemberExpression' &&
-			argument.type !== 'CallExpression'
-		) {
-			e.bind_invalid_expression(node);
-		}
-
 		mark_subtree_dynamic(context.path);
 
 		return;
@@ -261,7 +252,8 @@ export function BindDirective(node, context) {
 
 		node.metadata = {
 			binding_group_name: group_name,
-			parent_each_blocks: each_blocks
+			parent_each_blocks: each_blocks,
+			spread_binding: false
 		};
 	}
 
diff --git a/packages/svelte/src/compiler/phases/3-transform/client/visitors/BindDirective.js b/packages/svelte/src/compiler/phases/3-transform/client/visitors/BindDirective.js
index 8fdecd76e1..a55ba2a37a 100644
--- a/packages/svelte/src/compiler/phases/3-transform/client/visitors/BindDirective.js
+++ b/packages/svelte/src/compiler/phases/3-transform/client/visitors/BindDirective.js
@@ -21,8 +21,7 @@ export function BindDirective(node, context) {
 
 	let get, set;
 
-	// Handle SpreadElement by creating a variable declaration before visiting
-	if (node.expression.type === 'SpreadElement') {
+	if (node.metadata.spread_binding) {
 		const { get: getter, set: setter } = init_spread_bindings(node.expression, context);
 		get = getter;
 		set = setter;
diff --git a/packages/svelte/src/compiler/phases/3-transform/client/visitors/RegularElement.js b/packages/svelte/src/compiler/phases/3-transform/client/visitors/RegularElement.js
index 4296aa959e..c305a0cb6a 100644
--- a/packages/svelte/src/compiler/phases/3-transform/client/visitors/RegularElement.js
+++ b/packages/svelte/src/compiler/phases/3-transform/client/visitors/RegularElement.js
@@ -414,7 +414,7 @@ function setup_select_synchronization(value_binding, context) {
 
 	let bound = value_binding.expression;
 
-	if (bound.type === 'SequenceExpression') {
+	if (bound.type === 'SequenceExpression' || value_binding.metadata.spread_binding) {
 		return;
 	}
 
diff --git a/packages/svelte/src/compiler/phases/3-transform/client/visitors/shared/component.js b/packages/svelte/src/compiler/phases/3-transform/client/visitors/shared/component.js
index fc2d5b0833..5e678f4332 100644
--- a/packages/svelte/src/compiler/phases/3-transform/client/visitors/shared/component.js
+++ b/packages/svelte/src/compiler/phases/3-transform/client/visitors/shared/component.js
@@ -197,11 +197,14 @@ export function build_component(node, component_name, context) {
 				push_prop(b.init(attribute.name, value));
 			}
 		} else if (attribute.type === 'BindDirective') {
-			if (attribute.expression.type === 'SpreadElement') {
+			if (attribute.metadata.spread_binding) {
 				const { get, set } = init_spread_bindings(attribute.expression, context);
 
 				if (attribute.name === 'this') {
-					bind_this = attribute.expression;
+					bind_this = {
+						type: 'SpreadElement',
+						argument: attribute.expression
+					};
 				} else {
 					push_prop(b.get(attribute.name, [b.return(b.call(get))]), true);
 					push_prop(b.set(attribute.name, [b.stmt(b.call(set, b.id('$$value')))]), true);
diff --git a/packages/svelte/src/compiler/phases/3-transform/client/visitors/shared/utils.js b/packages/svelte/src/compiler/phases/3-transform/client/visitors/shared/utils.js
index c29f70ef98..7a443693d3 100644
--- a/packages/svelte/src/compiler/phases/3-transform/client/visitors/shared/utils.js
+++ b/packages/svelte/src/compiler/phases/3-transform/client/visitors/shared/utils.js
@@ -212,7 +212,7 @@ export function parse_directive_name(name) {
 export function build_bind_this(expression, value, context) {
 	const { state, visit } = context;
 	if (expression.type === 'SpreadElement') {
-		const { get, set } = init_spread_bindings(expression, context);
+		const { get, set } = init_spread_bindings(expression.argument, context);
 		return b.call('$.bind_this', value, set, get);
 	}
 
@@ -297,10 +297,7 @@ export function build_bind_this(expression, value, context) {
  * @param {MemberExpression} expression
  */
 export function validate_binding(state, binding, expression) {
-	if (
-		binding.expression.type === 'SequenceExpression' ||
-		binding.expression.type === 'SpreadElement'
-	) {
+	if (binding.expression.type === 'SequenceExpression' || binding.metadata.spread_binding) {
 		return;
 	}
 	// If we are referencing a $store.foo then we don't need to add validation
diff --git a/packages/svelte/src/compiler/phases/3-transform/server/visitors/shared/component.js b/packages/svelte/src/compiler/phases/3-transform/server/visitors/shared/component.js
index d2ba1091f4..050e5077bc 100644
--- a/packages/svelte/src/compiler/phases/3-transform/server/visitors/shared/component.js
+++ b/packages/svelte/src/compiler/phases/3-transform/server/visitors/shared/component.js
@@ -94,7 +94,7 @@ export function build_inline_component(node, expression, context) {
 			const value = build_attribute_value(attribute.value, context, false, true);
 			push_prop(b.prop('init', b.key(attribute.name), value));
 		} else if (attribute.type === 'BindDirective' && attribute.name !== 'this') {
-			if (attribute.expression.type === 'SpreadElement') {
+			if (attribute.metadata.spread_binding) {
 				const { get, set } = init_spread_bindings(attribute.expression, context);
 
 				push_prop(b.get(attribute.name, [b.return(b.call(get))]));
diff --git a/packages/svelte/src/compiler/phases/3-transform/server/visitors/shared/element.js b/packages/svelte/src/compiler/phases/3-transform/server/visitors/shared/element.js
index 2f9b8ab81e..0bb4ca87a6 100644
--- a/packages/svelte/src/compiler/phases/3-transform/server/visitors/shared/element.js
+++ b/packages/svelte/src/compiler/phases/3-transform/server/visitors/shared/element.js
@@ -119,8 +119,7 @@ export function build_element_attributes(node, context) {
 
 			let expression = /** @type {Expression} */ (context.visit(attribute.expression));
 
-			// Handle SpreadElement for bind directives
-			if (attribute.expression.type === 'SpreadElement') {
+			if (attribute.metadata.spread_binding) {
 				const { get } = init_spread_bindings(attribute.expression, context);
 				expression = b.call(get);
 			} else if (expression.type === 'SequenceExpression') {
@@ -134,7 +133,7 @@ export function build_element_attributes(node, context) {
 			} else if (
 				attribute.name === 'group' &&
 				attribute.expression.type !== 'SequenceExpression' &&
-				attribute.expression.type !== 'SpreadElement'
+				!attribute.metadata.spread_binding
 			) {
 				const value_attribute = /** @type {AST.Attribute | undefined} */ (
 					node.attributes.find((attr) => attr.type === 'Attribute' && attr.name === 'value')
diff --git a/packages/svelte/src/compiler/phases/3-transform/shared/spread_bindings.js b/packages/svelte/src/compiler/phases/3-transform/shared/spread_bindings.js
index cf496c8b85..6414be66b5 100644
--- a/packages/svelte/src/compiler/phases/3-transform/shared/spread_bindings.js
+++ b/packages/svelte/src/compiler/phases/3-transform/shared/spread_bindings.js
@@ -1,4 +1,4 @@
-/** @import { Expression, SpreadElement } from 'estree' */
+/** @import { Expression } from 'estree' */
 /** @import { ComponentContext as ClientContext } from '../client/types.js' */
 /** @import { ComponentContext as ServerContext } from '../server/types.js' */
 import * as b from '#compiler/builders';
@@ -6,14 +6,14 @@ import { dev, source } from '../../../state.js';
 
 /**
  * Initializes spread bindings for a SpreadElement in a bind directive.
- * @param {SpreadElement} spread_expression
+ * @param {Expression} spread_expression
  * @param {ClientContext | ServerContext} context
  * @returns {{ get: Expression, set: Expression }}
  */
 export function init_spread_bindings(spread_expression, { state, visit }) {
-	const visited_expression = /** @type {Expression} */ (visit(spread_expression.argument));
+	const expression = /** @type {Expression} */ (visit(spread_expression));
 	const expression_text = dev
-		? b.literal(source.slice(spread_expression.argument.start, spread_expression.argument.end))
+		? b.literal(source.slice(spread_expression.start, spread_expression.end))
 		: undefined;
 
 	const id = state.scope.generate('$$spread_binding');
@@ -22,7 +22,7 @@ export function init_spread_bindings(spread_expression, { state, visit }) {
 	state.init.push(
 		b.const(
 			b.array_pattern([get, set]),
-			b.call('$.validate_spread_bindings', visited_expression, expression_text)
+			b.call('$.validate_spread_bindings', expression, expression_text)
 		)
 	);
 
diff --git a/packages/svelte/src/compiler/types/legacy-nodes.d.ts b/packages/svelte/src/compiler/types/legacy-nodes.d.ts
index 389fc92332..259320ca40 100644
--- a/packages/svelte/src/compiler/types/legacy-nodes.d.ts
+++ b/packages/svelte/src/compiler/types/legacy-nodes.d.ts
@@ -7,7 +7,8 @@ import type {
 	MemberExpression,
 	ObjectExpression,
 	Pattern,
-	SequenceExpression
+	SequenceExpression,
+	SpreadElement
 } from 'estree';
 
 interface BaseNode {
@@ -50,7 +51,7 @@ export interface LegacyBinding extends BaseNode {
 	/** The 'x' in `bind:x` */
 	name: string;
 	/** The y in `bind:x={y}` */
-	expression: Identifier | MemberExpression | SequenceExpression;
+	expression: Identifier | MemberExpression | SequenceExpression | SpreadElement;
 }
 
 export interface LegacyBody extends BaseElement {
diff --git a/packages/svelte/src/compiler/types/template.d.ts b/packages/svelte/src/compiler/types/template.d.ts
index b3ae4fae5f..a48a7c15e7 100644
--- a/packages/svelte/src/compiler/types/template.d.ts
+++ b/packages/svelte/src/compiler/types/template.d.ts
@@ -212,11 +212,12 @@ export namespace AST {
 		/** The 'x' in `bind:x` */
 		name: string;
 		/** The y in `bind:x={y}` */
-		expression: Identifier | MemberExpression | SequenceExpression | SpreadElement;
+		expression: Identifier | MemberExpression | SequenceExpression;
 		/** @internal */
 		metadata: {
 			binding_group_name: Identifier;
 			parent_each_blocks: EachBlock[];
+			spread_binding: boolean;
 		};
 	}
 
diff --git a/packages/svelte/src/internal/shared/errors.js b/packages/svelte/src/internal/shared/errors.js
index ac06e510f0..a2056dd071 100644
--- a/packages/svelte/src/internal/shared/errors.js
+++ b/packages/svelte/src/internal/shared/errors.js
@@ -50,6 +50,23 @@ export function invalid_snippet_arguments() {
 	}
 }
 
+/**
+ * `%name%` must be a function or `undefined`
+ * @param {string} name
+ * @returns {never}
+ */
+export function invalid_spread_bindings(name) {
+	if (DEV) {
+		const error = new Error(`invalid_spread_bindings\n\`${name}\` must be a function or \`undefined\`\nhttps://svelte.dev/e/invalid_spread_bindings`);
+
+		error.name = 'Svelte error';
+
+		throw error;
+	} else {
+		throw new Error(`https://svelte.dev/e/invalid_spread_bindings`);
+	}
+}
+
 /**
  * `%name%(...)` can only be used during component initialisation
  * @param {string} name
@@ -114,21 +131,4 @@ export function svelte_element_invalid_this_value() {
 	} else {
 		throw new Error(`https://svelte.dev/e/svelte_element_invalid_this_value`);
 	}
-}
-
-/**
- * `%name%%member%` must be a function or `undefined`
- * @param {string} name
- * @returns {never}
- */
-export function invalid_spread_bindings(name) {
-	if (DEV) {
-		const error = new Error(`invalid_spread_bindings\n\`${name}\` must be a function or \`undefined\`\nhttps://svelte.dev/e/invalid_spread_bindings`);
-
-		error.name = 'Svelte error';
-
-		throw error;
-	} else {
-		throw new Error(`https://svelte.dev/e/invalid_spread_bindings`);
-	}
-}
+}
\ No newline at end of file
diff --git a/packages/svelte/types/index.d.ts b/packages/svelte/types/index.d.ts
index 90b5e18fb5..97e6f0f5a3 100644
--- a/packages/svelte/types/index.d.ts
+++ b/packages/svelte/types/index.d.ts
@@ -795,7 +795,7 @@ declare module 'svelte/attachments' {
 
 declare module 'svelte/compiler' {
 	import type { SourceMap } from 'magic-string';
-	import type { ArrayExpression, ArrowFunctionExpression, VariableDeclaration, VariableDeclarator, Expression, Identifier, MemberExpression, Node, ObjectExpression, Pattern, Program, ChainExpression, SimpleCallExpression, SequenceExpression, SpreadElement } from 'estree';
+	import type { ArrayExpression, ArrowFunctionExpression, VariableDeclaration, VariableDeclarator, Expression, Identifier, MemberExpression, Node, ObjectExpression, Pattern, Program, ChainExpression, SimpleCallExpression, SequenceExpression } from 'estree';
 	import type { Location } from 'locate-character';
 	/**
 	 * `compile` converts your `.svelte` source code into a JavaScript module that exports a component
@@ -1268,7 +1268,7 @@ declare module 'svelte/compiler' {
 			/** The 'x' in `bind:x` */
 			name: string;
 			/** The y in `bind:x={y}` */
-			expression: Identifier | MemberExpression | SequenceExpression | SpreadElement;
+			expression: Identifier | MemberExpression | SequenceExpression;
 		}
 
 		/** A `class:` directive */