svelte/packages/svelte/messages/compile-errors/script.md

bindable_invalid_location

$bindable() can only be used inside a $props() declaration

constant_assignment

Cannot assign to %thing%

constant_binding

Cannot bind to %thing%

declaration_duplicate

%name% has already been declared

declaration_duplicate_module_import

Cannot declare a variable with the same name as an import inside <script module>

derived_invalid_export

Cannot export derived state from a module. To expose the current derived value, export a function returning its value

dollar_binding_invalid

The $ name is reserved, and cannot be used for variables and imports

dollar_prefix_invalid

The $ prefix is reserved, and cannot be used for variables and imports

each_item_invalid_assignment

Cannot reassign or bind to each block argument in runes mode. Use the array and index variables instead (e.g. array[i] = value instead of entry = value)

effect_invalid_placement

$effect() can only be used as an expression statement

export_undefined

%name% is not defined

global_reference_invalid

%name% is an illegal variable name. To reference a global variable called %name%, use globalThis.%name%

host_invalid_placement

$host() can only be used inside custom element component instances

import_svelte_internal_forbidden

Imports of svelte/internal/* are forbidden. It contains private runtime code which is subject to change without notice. If you're importing from svelte/internal/* to work around a limitation of Svelte, please open an issue at https://github.com/sveltejs/svelte and explain your use case

invalid_arguments_usage

The arguments keyword cannot be used within the template or at the top level of a component

legacy_export_invalid

Cannot use export let in runes mode — use $props() instead

legacy_props_invalid

Cannot use $$props in runes mode

legacy_reactive_statement_invalid

$: is not allowed in runes mode, use $derived or $effect instead

legacy_rest_props_invalid

Cannot use $$restProps in runes mode

module_illegal_default_export

A component cannot have a default export

props_duplicate

Cannot use $props() more than once

props_illegal_name

Declaring or accessing a prop starting with $$ is illegal (they are reserved for Svelte internals)

props_invalid_identifier

$props() can only be used with an object destructuring pattern

props_invalid_pattern

$props() assignment must not contain nested properties or computed keys

props_invalid_placement

$props() can only be used at the top level of components as a variable declaration initializer

reactive_declaration_cycle

Cyclical dependency detected: %cycle%

rune_invalid_arguments

%rune% cannot be called with arguments

rune_invalid_arguments_length

%rune% must be called with %args%

rune_invalid_computed_property

Cannot access a computed property of a rune

rune_invalid_name

%name% is not a valid rune

rune_invalid_usage

Cannot use %rune% rune in non-runes mode

rune_missing_parentheses

Cannot use rune without parentheses

rune_removed

The %name% rune has been removed

rune_renamed

%name% is now %replacement%

runes_mode_invalid_import

%name% cannot be used in runes mode

snippet_invalid_export

An exported snippet can only reference things declared in a <script module>, or other exportable snippets

It's possible to export a snippet from a <script module> block, but only if it doesn't reference anything defined inside a non-module-level <script>. For example you can't do this...

<script module>
	export { greeting };
</script>

<script>
	let message = 'hello';
</script>

{#snippet greeting(name)}
	<p>{message} {name}!</p>
{/snippet}

...because greeting references message, which is defined in the second <script>.

snippet_parameter_assignment

Cannot reassign or bind to snippet parameter

state_invalid_export

Cannot export state from a module if it is reassigned. Either export a function returning the state value or only mutate the state value's properties

state_invalid_opaque_declaration

%rune%(...) must be declared with an array destructuring pattern (e.g. let [state, invalidate] = $state.opaque(data);)

state_invalid_placement

%rune%(...) can only be used as a variable declaration initializer or a class field

store_invalid_scoped_subscription

Cannot subscribe to stores that are not declared at the top level of the component

store_invalid_subscription

Cannot reference store value inside <script module>

store_invalid_subscription_module

Cannot reference store value outside a .svelte file

Using a $ prefix to refer to the value of a store is only possible inside .svelte files, where Svelte can automatically create subscriptions when a component is mounted and unsubscribe when the component is unmounted. Consider migrating to runes instead.

typescript_invalid_feature

TypeScript language features like %feature% are not natively supported, and their use is generally discouraged. Outside of <script> tags, these features are not supported. For use within <script> tags, you will need to use a preprocessor to convert it to JavaScript before it gets passed to the Svelte compiler. If you are using vitePreprocess, make sure to specifically enable preprocessing script tags (vitePreprocess({ script: true }))