non_bool_negation_expression

A negation operand must have a static type of 'bool'.

The analyzer produces this diagnostic when the operand of the unary negation operator (!) doesn't have the type bool.

The following code produces this diagnostic because x is an int when it must be a bool:

int x = 0;
bool y = !x;

Replace the operand with an expression that has the type bool:

int x = 0;
bool y = !(x > 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.