Fixed stubs generation for non-read-only properties with implicitly convertible types

Author: TimSchneider42

custom_stubgen.py

@@ -30,6 +30,11 @@ def write_module(self, module: Module, printer: Printer, to: Path, sub_dir: Opti
             for prop in cls.properties:
                 if prop.setter is not None:
                     self._patch_function(prop.setter)
+            for field in cls.fields:
+                if field.attribute.annotation is not None and field.attribute.annotation.name in self.alternative_types:
+                    converted_types = [ResolvedType(e) for e in self.alternative_types[field.attribute.annotation.name]]
+                    field.attribute.annotation = ResolvedType(
+                        QualifiedName.from_str("typing.Union"), [field.attribute.annotation] + converted_types)
         super().write_module(module, printer, to, sub_dir=sub_dir)