osa1

import 'my_library.dart';

// Same class B in Strange Dart 9.1, but this time it's accepted.
class B implements A {}

void main() {
  wat(B()); // _a getters and setters redirect to noSuchMethod
}

osa1

// Private members are not part of a class's interface, but implementing
// classes need to implement them.
//
// ... except when the class being implemented is in a separate library. See
// the second part: https://gist.github.com/osa1/a6b70f36d1041996c3ff7fa12c7589d8

class A {
  int _a = 1;
  int _b = 2;

osa1

class A {
  @override
  Type get runtimeType => int;
}

class B<T> {}

void main() {
  print(A().runtimeType); // int
  print(B<A>().runtimeType); // B<A>

osa1

// Almost by definition, if I'm able to pass X where Y is expected, then X is a
// subtype of Y.
//
// In Dart, this mostly holds, but `dynamic` is an exception. I can pass
// `dynamic` everywhere, but it's not really a subtype of anything.

void f(int a) {}

class C<A> {}

osa1

module Lexer
    ( Token(..)
    , TokenPos
    , tokenize
    ) where

import Text.ParserCombinators.Parsec hiding (token, tokens)
import Control.Applicative ((<*), (*>), (<$>), (<*>))

data Token = Ide String

osa1

class C {
  dynamic get a {
    print('C.a getter called');
    return (x) => print('C.a return value called');
  }
}

void main() {
  var x = C();

osa1

class A {
  void f() {
    print('A.f called');
  }
}

class B implements A {
  void f({int test}); // optional non-nullable with no default value, also not a valid override

  // `f` above is not valid without a `noSuchMethod`

osa1

class A {
  void f() {}
}

extension B on A {
  void g() {}
}

void main() {
  final a = A();

osa1

class A {
  void f() {
    print('A.f called');
  }
}

class B extends A {
  @override
  void f();
}

osa1

void voidFun() => 123;

class A<T> {
  T x;
  
  A (this.x);
  
  Object? getX() => x;
}