unnecessary_ nan_ comparison
A double can't equal 'double.nan', so the condition is always 'false'.
A double can't equal 'double.nan', so the condition is always 'true'.
Description
#
The analyzer produces this diagnostic when a value is compared to
double.nan
using either
==
or
!=
.
Dart follows the
IEEE 754
floating-point standard for the semantics of
floating point operations, which states that, for any floating point value
x
(including NaN, positive infinity, and negative infinity),
NaN == x
is always falseNaN != x
is always true
As a result, comparing any value to NaN is pointless because the result is already known (based on the comparison operator being used).
Example
#
The following code produces this diagnostic because
d
is being compared
to
double.nan
:
bool isNaN(double d) => d == double.nan;
Common fixes
#Use the getter double.isNaN
instead:
bool isNaN(double d) => d.isNaN;
Unless stated otherwise, the documentation on this site reflects Dart 3.9.2. Page last updated on 2025-9-1. View source or report an issue.