don't alias constant expressions

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

@@ -5,6 +5,7 @@ import * as b from '#compiler/builders';
 import { dev } from '../../../../state.js';
 import { get_parent } from '../../../../utils/ast.js';
 import { get_name } from '../../../nodes.js';
+import { is_constant } from '../../../scope.js';
 
 /**
  * @param {ClassBody} node
@@ -61,6 +62,20 @@ export function ClassBody(node, context) {
 				);
 				continue;
 			}
+			if (is_constant(computed_key, context.state.scope)) {
+				body.push(
+					b.prop_def(field.key, null),
+					b.method('get', computed_key, [], [b.return(b.call('$.get', member))], true),
+					b.method(
+						'set',
+						computed_key,
+						[b.id('value')],
+						[b.stmt(b.call('$.set', member, b.id('value'), should_proxy && b.true))],
+						true
+					)
+				);
+				continue;
+			}
 			const key = context.state.scope.generate('key');
 			computed_field_declarations.push(b.let(key));
 
@@ -163,6 +178,42 @@ export function ClassBody(node, context) {
 					b.literal(`${declaration.id?.name ?? '[class]'}[computed key]`)
 				);
 			}
+			const computed_key = /** @type {Expression} */ (context.visit(field.computed_key));
+			const evaluation = context.state.scope.evaluate(computed_key);
+			if (evaluation.is_known) {
+				body.push(
+					b.prop_def(field.key, call),
+					b.method(
+						'get',
+						b.literal(evaluation.value),
+						[],
+						[b.return(b.call('$.get', member))],
+						true
+					),
+					b.method(
+						'set',
+						b.literal(evaluation.value),
+						[b.id('value')],
+						[b.stmt(b.call('$.set', member, b.id('value'), should_proxy && b.true))],
+						true
+					)
+				);
+				continue;
+			}
+			if (is_constant(computed_key, context.state.scope)) {
+				body.push(
+					b.prop_def(field.key, call),
+					b.method('get', computed_key, [], [b.return(b.call('$.get', member))], true),
+					b.method(
+						'set',
+						computed_key,
+						[b.id('value')],
+						[b.stmt(b.call('$.set', member, b.id('value'), should_proxy && b.true))],
+						true
+					)
+				);
+				continue;
+			}
 			const key = context.state.scope.generate('key');
 			computed_field_declarations.push(b.let(key));
 
@@ -170,11 +221,7 @@ export function ClassBody(node, context) {
 				b.prop_def(field.key, call),
 				b.method(
 					'get',
-					b.assignment(
+					b.assignment('=', b.id(key), computed_key),
-						'=',
-						b.id(key),
-						/** @type {Expression} */ (context.visit(field.computed_key))
-					),
 					[],
 					[b.return(b.call('$.get', member))],
 					true

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

@@ -2,6 +2,7 @@
 /** @import { Context } from '../types.js' */
 import * as b from '#compiler/builders';
 import { get_name } from '../../../nodes.js';
+import { is_constant } from '../../../scope.js';
 
 /**
  * @param {ClassBody} node
@@ -34,17 +35,43 @@ export function ClassBody(node, context) {
 
 		const member = b.member(b.this, field.key);
 		if (typeof name !== 'string' && field.computed_key) {
+			const computed_key = /** @type {Expression} */ (context.visit(field.computed_key));
+			const evaluation = context.state.scope.evaluate(computed_key);
+			if (evaluation.is_known) {
+				body.push(
+					b.prop_def(field.key, null),
+					b.method('get', b.literal(evaluation.value), [], [b.return(b.call(member))], true),
+					b.method(
+						'set',
+						b.literal(evaluation.value),
+						[b.id('$$value')],
+						[b.return(b.call(member, b.id('$$value')))],
+						true
+					)
+				);
+				continue;
+			}
+			if (is_constant(computed_key, context.state.scope)) {
+				body.push(
+					b.prop_def(field.key, null),
+					b.method('get', computed_key, [], [b.return(b.call(member))], true),
+					b.method(
+						'set',
+						computed_key,
+						[b.id('$$value')],
+						[b.return(b.call(member, b.id('$$value')))],
+						true
+					)
+				);
+				continue;
+			}
 			const key = context.state.scope.generate('key');
 			computed_field_declarations.push(b.let(key));
 			body.push(
 				b.prop_def(field.key, null),
 				b.method(
 					'get',
-					b.assignment(
+					b.assignment('=', b.id(key), computed_key),
-						'=',
-						b.id(key),
-						/** @type {Expression} */ (context.visit(field.computed_key))
-					),
 					[],
 					[b.return(b.call(member))],
 					true
@@ -133,6 +160,23 @@ export function ClassBody(node, context) {
 				);
 				continue;
 			}
+			if (is_constant(computed_key, context.state.scope)) {
+				body.push(
+					b.prop_def(
+						field.key,
+						/** @type {CallExpression} */ (context.visit(field.value, child_state))
+					),
+					b.method('get', computed_key, [], [b.return(b.call(member))], true),
+					b.method(
+						'set',
+						computed_key,
+						[b.id('$$value')],
+						[b.return(b.call(member, b.id('$$value')))],
+						true
+					)
+				);
+				continue;
+			}
 			const key = context.state.scope.generate('key');
 			computed_field_declarations.push(b.let(key));
 			body.push(
@@ -142,11 +186,7 @@ export function ClassBody(node, context) {
 				),
 				b.method(
 					'get',
-					b.assignment(
+					b.assignment('=', b.id(key), computed_key),
-						'=',
-						b.id(key),
-						/** @type {Expression} */ (context.visit(field.computed_key))
-					),
 					[],
 					[b.return(b.call(member))],
 					true

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

@@ -1358,6 +1358,70 @@ export function get_rune(node, scope) {
 	return keypath;
 }
 
+/**
+ * @param {Expression} expression
+ * @param {Scope} scope
+ */
+export function is_constant(expression, scope) {
+	const evaluation = scope.evaluate(expression);
+	if (evaluation.is_known) {
+		return true;
+	}
+	let constant = true;
+	walk(/** @type {Node} */ (expression), null, {
+		Identifier(node, { path, stop }) {
+			if (is_reference(node, /** @type {Node} */ (path.at(-1)))) {
+				const binding = scope.get(node.name);
+				if (!binding || binding.reassigned) {
+					constant = false;
+					stop();
+					return;
+				}
+			}
+		},
+		ArrowFunctionExpression(_, { stop }) {
+			constant = false;
+			stop();
+		},
+		FunctionExpression(_, { stop }) {
+			constant = false;
+			stop();
+		},
+		ClassExpression(_, { stop }) {
+			constant = false;
+			stop();
+		},
+		MemberExpression(_, { stop }) {
+			constant = false;
+			stop();
+		},
+		CallExpression(node, { stop }) {
+			if (scope.evaluate(node).is_known) {
+				return;
+			}
+			constant = false;
+			stop();
+		},
+		UpdateExpression(_, { stop }) {
+			constant = false;
+			stop();
+		},
+		AssignmentExpression(_, { stop }) {
+			constant = false;
+			stop();
+		},
+		UnaryExpression(node, { next, stop }) {
+			if (node.operator === 'delete') {
+				constant = false;
+				stop();
+				return;
+			}
+			next();
+		}
+	});
+	return constant;
+}
+
 /**
  * Returns the name of the rune if the given expression is a `CallExpression` using a rune.
  * @param {Expression | Super} node