40 columns                              |
>>> Top-level variable.
  external   final   a ,  b  ;
  external   final    Set < int  >  a ,  b  ;
  external   var   a  ;
  external   List < int >   a  ;
<<<
external final a, b;
external final Set<int> a, b;
external var a;
external List<int> a;
>>> Static field.
class C {
  external  static    final   a ,  b  ;
external    static  final    Set < int  >  a ,  b  ;
   external   static   var   a  ;
  external  static    List < int >   a  ;
}
<<<
class C {
  external static final a, b;
  external static final Set<int> a, b;
  external static var a;
  external static List<int> a;
}
>>> Instance field.
class C {
  external   final   a ,  b  ;
  external   final    Set < String  >  a ,  b  ;
  external   var   a  ;
  external   List < int >   a  ;
}
<<<
class C {
  external final a, b;
  external final Set<String> a, b;
  external var a;
  external List<int> a;
}
>>> Top-level function.
external  int  function();
external  int  get getter;
external  void  set setter(int value);
<<<
external int function();
external int get getter;
external void set setter(int value);
>>> Instance member.
class A {
  external  int  function();
  external  int  get getter;
  external  void  set setter(int value);
}
<<<
class A {
  external int function();
  external int get getter;
  external void set setter(int value);
}
>>> Static member.
class A {
  external  static  int function();
  external  static  int get getter;
  external  static  void set setter(int value);
}
<<<
class A {
  external static int function();
  external static int get getter;
  external static void set setter(
    int value,
  );
}
>>> Constructor.
class A {
  external A();
  external const A.constant();
  external factory A.fact();
  external const factory A.constantFact();
}
<<<
class A {
  external A();
  external const A.constant();
  external factory A.fact();
  external const factory A.constantFact();
}
>>> Don't split after `external`.
class Foo {
  external var soMuchSoVeryLongFieldNameHere;
  external SuperLongTypeAnnotation field;
}
<<<
class Foo {
  external var soMuchSoVeryLongFieldNameHere;
  external SuperLongTypeAnnotation
  field;
}