avoid_returning_null

Avoid returning null from members whose return type is bool, double, int, or num.

NOTE: This rule is removed in Dart 3.3.0; it is no longer functional.

AVOID returning null from members whose return type is bool, double, int, or num.

Functions that return primitive types such as bool, double, int, and num are generally expected to return non-nullable values. Thus, returning null where a primitive type was expected can lead to runtime exceptions.

BAD:

bool getBool() => null;
num getNum() => null;
int getInt() => null;
double getDouble() => null;

GOOD:

bool getBool() => false;
num getNum() => -1;
int getInt() => -1;
double getDouble() => -1.0;

To enable the avoid_returning_null rule, add avoid_returning_null under linter > rules in your analysis_options.yaml file:

linter:
  rules:
    - avoid_returning_null

If you're instead using the YAML map syntax to configure linter rules, add avoid_returning_null: true under linter > rules:

linter:
  rules:
    avoid_returning_null: true

Unless stated otherwise, the documentation on this site reflects Dart 3.7.0. Page last updated on 2025-01-27. View source or report an issue.