type_argument_not_matching_bounds

'{0}' doesn't conform to the bound '{2}' of the type parameter '{1}'.

The analyzer produces this diagnostic when a type argument isn't the same as or a subclass of the bounds of the corresponding type parameter.

The following code produces this diagnostic because String isn't a subclass of num:

class A<E extends num> {}

var a = A<String>();

Change the type argument to be a subclass of the bounds:

class A<E extends num> {}

var a = A<int>();

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.