prefer_const_literals_to_create_immutables

Use 'const' literals as arguments to constructors of '@immutable' classes.

The analyzer produces this diagnostic when a non-const list, map, or set literal is passed as an argument to a constructor declared in a class annotated with @immutable.

The following code produces this diagnostic because the list literal ([1]) is being passed to a constructor in an immutable class but isn't a constant list:

import 'package:meta/meta.dart';

@immutable
class C {
  final f;

  const C(this.f);
}

C c = C([1]);

If the context can be made a constant context, then do so:

import 'package:meta/meta.dart';

@immutable
class C {
  final f;

  const C(this.f);
}

const C c = C([1]);

If the context can't be made a constant context but the constructor can be invoked using const, then add const before the constructor invocation:

import 'package:meta/meta.dart';

@immutable
class C {
  final f;

  const C(this.f);
}

C c = const C([1]);

If the context can't be made a constant context and the constructor can't be invoked using const, then add the keyword const before the collection literal:

import 'package:meta/meta.dart';

@immutable
class C {
  final f;

  const C(this.f);
}

C c = C(const [1]);

Unless stated otherwise, the documentation on this site reflects Dart 3.8.1. Page last updated on 2025-05-08. View source or report an issue.