error on rest prop and duplicate props

packages/svelte/src/compiler/errors.js

@@ -180,6 +180,9 @@ const runes = {
 	'invalid-props-id': () => `$props() can only be used with an object destructuring pattern`,
 	'invalid-props-pattern': () =>
 		`$props() assignment must not contain nested properties or computed keys`,
+	'duplicate-prop-name': () =>
+		`Cannot use the same prop name more than once across $props() and $props.bindable()`,
+	'invalid-props-rest-element': () => `Cannot use ...rest parameter with $props.bindable()`,
 	'invalid-props-location': () =>
 		`$props() can only be used at the top level of components as a variable declaration initializer`,
 	/** @param {string} rune */

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

@@ -422,6 +422,7 @@ export function analyze_component(root, options) {
 				options,
 				ast_type: ast === instance.ast ? 'instance' : ast === template.ast ? 'template' : 'module',
 				parent_element: null,
+				all_prop_names: new Set(),
 				has_props_rune: [false, false],
 				component_slots: new Set(),
 				expression: null,
@@ -446,6 +447,7 @@ export function analyze_component(root, options) {
 				analysis,
 				options,
 				parent_element: null,
+				all_prop_names: new Set(),
 				has_props_rune: [false, false],
 				ast_type: ast === instance.ast ? 'instance' : ast === template.ast ? 'template' : 'module',
 				instance_scope: instance.scope,
@@ -525,6 +527,16 @@ export function analyze_component(root, options) {
 		}
 	}
 
+	if (analysis.runes) {
+		const props = new Set();
+		for (const [name, binding] of instance.scope.declarations) {
+			if (binding.kind === 'prop' || binding.kind === 'bindable_prop') {
+				if (props.has(binding)) {
+				}
+			}
+		}
+	}
+
 	if (analysis.css.ast) {
 		analyze_css(analysis.css.ast, analysis);
 

packages/svelte/src/compiler/phases/2-analyze/types.d.ts

@@ -15,6 +15,8 @@ export interface AnalysisState {
 	options: ValidatedCompileOptions;
 	ast_type: 'instance' | 'template' | 'module';
 	parent_element: string | null;
+	/** Names of $props() and $props.bindable() */
+	all_prop_names: Set<string>;
 	has_props_rune: [props: boolean, bindings: boolean];
 	/** Which slots the current parent component has */
 	component_slots: Set<string>;

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

@@ -1092,9 +1092,17 @@ export const validation_runes = merge(validation, a11y_validators, {
 					const value =
 						property.value.type === 'AssignmentPattern' ? property.value.left : property.value;
 
-					if (value.type !== 'Identifier') {
+					if (value.type !== 'Identifier' || property.key.type !== 'Identifier') {
 						error(property, 'invalid-props-pattern');
 					}
+
+					if (state.all_prop_names.has(property.key.name)) {
+						error(property, 'duplicate-prop-name');
+					}
+
+					state.all_prop_names.add(property.key.name);
+				} else if (rune === '$props.bindable') {
+					error(property, 'invalid-props-rest-element');
 				}
 			}
 		}

packages/svelte/tests/compiler-errors/samples/props-bindable-rest/_config.js

@@ -0,0 +1,9 @@
+import { test } from '../../test';
+
+export default test({
+	error: {
+		code: 'invalid-props-rest-element',
+		message: 'Cannot use ...rest parameter with $props.bindable()',
+		position: [53, 62]
+	}
+});

packages/svelte/tests/compiler-errors/samples/props-bindable-rest/main.svelte

@@ -0,0 +1,4 @@
+<script>
+	let { foo, ...ok } = $props();
+	let { bar, ...not_ok } = $props.bindable();
+</script>

packages/svelte/tests/compiler-errors/samples/props-duplicate-destructuring/_config.js

@@ -0,0 +1,9 @@
+import { test } from '../../test';
+
+export default test({
+	error: {
+		code: 'duplicate-prop-name',
+		message: 'Cannot use the same prop name more than once across $props() and $props.bindable()',
+		position: [44, 50]
+	}
+});

packages/svelte/tests/compiler-errors/samples/props-duplicate-destructuring/main.svelte

@@ -0,0 +1,4 @@
+<script>
+	let { foo: a } = $props();
+	let { foo: b } = $props.bindable();
+</script>