collection_element_from_deferred_library

Constant values from a deferred library can't be used as keys in a 'const' map literal.

Constant values from a deferred library can't be used as values in a 'const' constructor.

Constant values from a deferred library can't be used as values in a 'const' list literal.

Constant values from a deferred library can't be used as values in a 'const' map literal.

Constant values from a deferred library can't be used as values in a 'const' set literal.

The analyzer produces this diagnostic when a collection literal that is either explicitly (because it's prefixed by the const keyword) or implicitly (because it appears in a constant context) a constant contains a value that is declared in a library that is imported using a deferred import. Constants are evaluated at compile time, and values from deferred libraries aren't available at compile time.

For more information, check out Lazily loading a library.

Given a file a.dart that defines the constant zero:

const zero = 0;

The following code produces this diagnostic because the constant list literal contains a.zero, which is imported using a deferred import:

import 'a.dart' deferred as a;

var l = const [a.zero];

If the collection literal isn't required to be constant, then remove the const keyword:

import 'a.dart' deferred as a;

var l = [a.zero];

If the collection is required to be constant and the imported constant must be referenced, then remove the keyword deferred from the import:

import 'a.dart' as a;

var l = const [a.zero];

If you don't need to reference the constant, then replace it with a suitable value:

var l = const [0];

Unless stated otherwise, the documentation on this site reflects Dart 3.8.0. Page last updated on 2025-05-08. View source or report an issue.