|  | library /*isNonNullableByDefault*/; | 
|  | import self as self; | 
|  | import "dart:core" as core; | 
|  |  | 
|  | class A<T extends core::Object? = dynamic> extends core::Object { | 
|  | synthetic constructor •() → self::A<self::A::T%> | 
|  | : super core::Object::•() | 
|  | ; | 
|  | method f<U extends core::Object? = dynamic>(covariant-by-class core::Map<self::A::T%, self::A::f::U%> m) → void {} | 
|  | } | 
|  | class B extends self::A<core::String> { | 
|  | synthetic constructor •() → self::B | 
|  | : super self::A::•() | 
|  | ; | 
|  | method f<V extends core::Object? = dynamic>(covariant-by-class core::Map<core::String, self::B::f::V%> m) → void {} | 
|  | } | 
|  | static method main() → dynamic {} |