separate reassignment from mutation

packages/svelte/src/compiler/migrate/index.js

@@ -331,10 +331,7 @@ const instance_script = {
 
 				const binding = /** @type {Compiler.Binding} */ (state.scope.get(declarator.id.name));
 
-				if (
-					state.analysis.uses_props &&
-					(declarator.init || binding.mutated || binding.reassigned)
-				) {
+				if (state.analysis.uses_props && (declarator.init || binding.updated)) {
 					throw new Error(
 						'$$props is used together with named props in a way that cannot be automatically migrated.'
 					);
@@ -350,7 +347,7 @@ const instance_script = {
 							)
 						: '',
 					optional: !!declarator.init,
-					bindable: binding.mutated || binding.reassigned,
+					bindable: binding.updated,
 					...extract_type_and_comment(declarator, state.str, path)
 				});
 				state.props_insertion_point = /** @type {number} */ (declarator.end);

packages/svelte/src/compiler/phases/2-analyze/index.js

@@ -458,7 +458,7 @@ export function analyze_component(root, source, options) {
 			for (const { node, path } of binding.references) {
 				if (node === binding.node) continue;
 
-				if (binding.mutated) {
+				if (binding.updated) {
 					if (
 						path[path.length - 1].type === 'StyleDirective' ||
 						path.some((node) => node.type === 'Fragment') ||
@@ -477,7 +477,7 @@ export function analyze_component(root, source, options) {
 				const scope = /** @type {Scope} */ (template.scopes.get(node));
 
 				for (const binding of scope.declarations.values()) {
-					if (binding.mutated) {
+					if (binding.updated) {
 						const state = { scope: /** @type {Scope} */ (scope.parent), scopes: template.scopes };
 
 						walk(node.expression, state, {
@@ -491,6 +491,7 @@ export function analyze_component(root, source, options) {
 
 									if (binding && binding.kind === 'normal') {
 										binding.kind = 'state';
+										binding.mutated = binding.updated = true;
 									}
 								}
 							}

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

@@ -134,7 +134,7 @@ function get_delegated_event(event_name, handler, context) {
 			return unhoisted;
 		}
 
-		if (binding !== null && binding.initial !== null && !binding.mutated && !binding.is_called) {
+		if (binding !== null && binding.initial !== null && !binding.updated && !binding.is_called) {
 			const binding_type = binding.initial.type;
 
 			if (
@@ -188,7 +188,7 @@ function get_delegated_event(event_name, handler, context) {
 				(((!context.state.analysis.runes && binding.kind === 'each') ||
 					// or any normal not reactive bindings that are mutated.
 					binding.kind === 'normal') &&
-					binding.mutated))
+					binding.updated))
 		) {
 			return unhoisted;
 		}

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

@@ -39,7 +39,7 @@ export function BindDirective(node, context) {
 					binding.kind !== 'bindable_prop' &&
 					binding.kind !== 'each' &&
 					binding.kind !== 'store_sub' &&
-					!binding.mutated))
+					!binding.updated)) // TODO wut?
 		) {
 			e.bind_invalid_value(node.expression);
 		}

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

@@ -17,7 +17,7 @@ export function ExportSpecifier(node, context) {
 			});
 
 			const binding = context.state.scope.get(node.local.name);
-			if (binding) binding.reassigned = true;
+			if (binding) binding.reassigned = binding.updated = true;
 		}
 	} else {
 		validate_export(node, context.state.scope, node.local.name);

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

@@ -235,7 +235,7 @@ export function is_prop_source(binding, state) {
 			binding.initial ||
 			// Until legacy mode is gone, we also need to use the prop source when only mutated is true,
 			// because the parent could be a legacy component which needs coarse-grained reactivity
-			binding.mutated)
+			binding.updated)
 	);
 }
 

packages/svelte/src/compiler/phases/scope.js

@@ -685,9 +685,13 @@ export function create_scopes(ast, root, allow_reactive_declarations, parent) {
 			const binding = left && scope.get(left.name);
 
 			if (binding !== null && left !== binding.node) {
-				// TODO we should probably distinguish between these?
-				binding.mutated = true;
-				binding.reassigned ||= left === expression;
+				binding.updated = true;
+
+				if (left === expression) {
+					binding.reassigned = true;
+				} else {
+					binding.mutated = true;
+				}
 			}
 		}
 	}

packages/svelte/src/compiler/types/index.d.ts

@@ -300,6 +300,8 @@ export interface Binding {
 	references: { node: Identifier; path: SvelteNode[] }[];
 	mutated: boolean;
 	reassigned: boolean;
+	/** `true` if mutated _or_ reassigned */
+	updated: boolean;
 	scope: Scope;
 	/** For `legacy_reactive`: its reactive dependencies */
 	legacy_dependencies: Binding[];