expression_in_map

Expressions can't be used in a map literal.

The analyzer produces this diagnostic when the analyzer finds an expression, rather than a map entry, in what appears to be a map literal.

The following code produces this diagnostic:

var map = <String, int>{'a': 0, 'b': 1, 'c'};

If the expression is intended to compute either a key or a value in an entry, fix the issue by replacing the expression with the key or the value. For example:

var map = <String, int>{'a': 0, 'b': 1, 'c': 2};

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.