[BUG] [Dart] Serializers generation fails when additionalProperties = true for nested classes

[feykro]

Description

I'm generator dart code for a Flutter project.
Let's say I have a class A, which has a few fields as well as "additionalProperties: true" in the openapi yaml file.
Now I have class B, and one of its fields is an instance of A.

If this class B is present in an endpoint's request object, it will create a bug in the "_deserializeProperties" where we get: A value of type 'ClassB' can't be assigned to a variable of type 'ClassBBuilder?'.

openapi-generator version

MacOS, version 7.12.0
Dart version 3.9.0

Generation Details

Generation threw no errors or warning and completed as expected.