nullable_type_in_extends_clause
A class can't extend a nullable type.
Description
#The analyzer produces this diagnostic when a class declaration uses an
extends clause to specify a superclass, and the superclass is followed by
a ?.
It isn't valid to specify a nullable superclass because doing so would have
no meaning; it wouldn't change either the interface or implementation being
inherited by the class containing the extends clause.
Note, however, that it is valid to use a nullable type as a type argument
to the superclass, such as class A extends B<C?> {}.
Example
#The following code produces this diagnostic because A? is a nullable
type, and nullable types can't be used in an extends clause:
class A {}
class B extends A? {}Common fixes
#Remove the question mark from the type:
class A {}
class B extends A {}除非另有说明，文档之所提及适用于 Dart 3.7.3 版本，本页面最后更新时间: 2025-05-08。 查看文档源码 或者 报告页面问题。