unnecessary_type_check

Unnecessary type check; the result is always 'false'.

Unnecessary type check; the result is always 'true'.

The analyzer produces this diagnostic when the value of a type check (using either is or is!) is known at compile time.

The following code produces this diagnostic because the test a is Object? is always true:

bool f<T>(T a) => a is Object?;

If the type check doesn't check what you intended to check, then change the test:

bool f<T>(T a) => a is Object;

If the type check does check what you intended to check, then replace the type check with its known value or completely remove it:

bool f<T>(T a) => true;

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.