avoid_as

Avoid using as.

NOTE: This rule was removed from the SDK in Dart 3; it is no longer functional. Its advice is compiler-specific and mostly obsolete with null safety.

AVOID using as.

If you know the type is correct, use an assertion or assign to a more narrowly-typed variable (this avoids the type check in release mode; as is not compiled out in release mode). If you don't know whether the type is correct, check using is (this avoids the exception that as raises).

BAD:

(pm as Person).firstName = 'Seth';

GOOD:

if (pm is Person)
  pm.firstName = 'Seth';

but certainly not

BAD:

try {
   (pm as Person).firstName = 'Seth';
} on CastError { }

Note that an exception is made in the case of dynamic since the cast has no performance impact.

OK:

HasScrollDirection scrollable = renderObject as dynamic;

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

linter:
  rules:
    - avoid_as

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

linter:
  rules:
    avoid_as: true