Tests for `void`.

tests/language/void_type2_test.dart

+// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// Dart test for type checks involving the void type.
+
+void use(dynamic x) { }
+
+void testVoidParam(void x) {
+  x;  /// param_stmt: ok
+  true ? x : x;  /// param_conditional: ok

[eernst, 2017/07/10 16:05:33]

We decided at a language meeting long ago that the conditional expression should
not be included, which is the reason why I've omitted that construct from the
allowed contexts for void expressions in the informal spec. If we want to add it
again we should make that decision.

+  for (x; false; x) {}   /// param_for: ok
+  use(x);   /// param_argument: error
+  use(x as Object);  /// param_as: error?

[eernst, 2017/07/10 16:05:32]

It was my understanding that we had agreed to allow explicit casts out of
`void`, but I recently learned that Lasse does not support this. So we need to
adjust this to a plain `error`, or we need to adjust the informal spec.

+  void y = x;   /// param_void_init: error
+  dynamic y = x;  /// param_dynamic_init: error
+  x is Object;   /// param_is: error

[eernst, 2017/07/10 16:05:33]

In the informal spec this is allowed, but as I noted in a comment I do not
remember having had clear support for that decision in the language team. I can
go either way, Lasse prefers to prohibit it. In any case either this should be
adjusted, or the informal spec should.

+  throw x;   /// param_throw: error
+  [x];   /// param_literal_list_init: error
+  var m1 = {4: x};   /// param_literal_map_value_init: error
+  var m2 = {x : 4};   /// param_literal_map_key_init: error
+  Map<dynamic, dynamic> m3 = {4: x};  /// param_literal_map_value_init2: error
+  Map<dynamic, dynamic> m4 = {x : 4};  /// param_literal_map_key_init2: error
+  x ?? 499;  /// param_null_equals2: error
+  null ?? x;  /// param_null_equals2: error
+  return x;   /// param_return: error
+  while (x) {};  /// param_while: error
+  do {} while (x);  /// param_do_while: error
+  for (var v in x) {}   /// param_for_in: error
+  for (x in [1, 2]) {}  /// param_for_in2: ok
+  x += 1;  /// param_plus_eq: error
+  x.toString();  /// param_toString: error
+  x?.toString();  /// param_null_dot: error
+  x..toString();  /// param_cascade: error
+}
+
+void testVoidCall(void f()) {
+  f();  /// call_stmt: ok
+  true ? f() : f();  /// call_conditional: ok

[eernst, 2017/07/10 16:05:32]

Should get the same treatment as line 11.

+  for (f(); false; f()) {}   /// call_for: ok
+  use(f());   /// call_argument: error
+  use(f() as Object);  /// call_as: error?

[eernst, 2017/07/10 16:05:30]

Should get the same treatment as line 14.

+  void y = f();   /// call_void_init: error
+  dynamic y = f();  /// call_dynamic_init: error
+  f() is Object;   /// call_is: error

[eernst, 2017/07/10 16:05:33]

Should get the same treatment as line 17.

+  throw f();   /// call_throw: error
+  [f()];   /// call_literal_list_init: error
+  var m1 = {4: f() };   /// call_literal_map_value_init: error
+  var m2 = { f(): 4};   /// call_literal_map_key_init: error
+  Map<dynamic, dynamic> m3 = {4: f() };  /// call_literal_map_value_init2: error
+  Map<dynamic, dynamic> m4 = { f(): 4};  /// call_literal_map_key_init2: error
+  f() ?? 499;  /// call_null_equals2: error
+  null ?? f();  /// call_null_equals2: error
+  return f();   /// call_return: error
+  while (f()) {};  /// call_while: error
+  do {} while (f());  /// call_do_while: error
+  for (var v in f()) {}   /// call_for_in: error
+  f().toString();  /// call_toString: error
+  f()?.toString();  /// call_null_dot: error
+  f()..toString();  /// call_cascade: error
+}
+
+void testVoidLocal() {
+  void x;
+  x = 42;   /// local_assign: ok;
+  x;  /// local_stmt: ok
+  true ? x : x;  /// local_conditional: ok

[eernst, 2017/07/10 16:05:31]

Should get the same treatment as line 11.

+  for (x; false; x) {}   /// local_for: ok
+  use(x);   /// local_argument: error
+  use(x as Object);  /// local_as: error?

[eernst, 2017/07/10 16:05:33]

Should get the same treatment as line 14.

+  void y = x;   /// local_void_init: error
+  dynamic y = x;  /// local_dynamic_init: error
+  x is Object;   /// local_is: error

[eernst, 2017/07/10 16:05:32]

Should get the same treatment as line 17.

+  throw x;   /// local_throw: error
+  [x];   /// local_literal_list_init: error
+  var m1 = {4: x};   /// local_literal_map_value_init: error
+  var m2 = {x : 4};   /// local_literal_map_key_init: error
+  Map<dynamic, dynamic> m3 = {4: x};  /// local_literal_map_value_init2: error
+  Map<dynamic, dynamic> m4 = {x : 4};  /// local_literal_map_key_init2: error
+  x ?? 499;  /// local_null_equals2: error
+  null ?? x;  /// local_null_equals2: error
+  return x;   /// local_return: error
+  while (x) {};  /// local_while: error
+  do {} while (x);  /// local_do_while: error
+  for (var v in x) {}   /// local_for_in: error
+  for (x in [1, 2]) {}  /// local_for_in2: ok
+  x += 1;  /// local_plus_eq: error
+  x.toString();  /// local_toString: error
+  x?.toString();  /// local_null_dot: error
+  x..toString();  /// local_cascade: error
+}
+
+void testVoidFinalLocal() {
+  final void x;
+  x = 42;   /// final_local_assign: error;
+  x;  /// final_local_stmt: ok
+  true ? x : x;  /// final_local_conditional: ok

[eernst, 2017/07/10 16:05:33]

Should get the same treatment as line 11.

+  for (x; false; x) {}   /// final_local_for: ok
+  use(x);   /// final_local_argument: error
+  use(x as Object);  /// final_local_as: error?

[eernst, 2017/07/10 16:05:31]

Should get the same treatment as line 14.

+  void y = x;   /// final_local_void_init: error
+  dynamic y = x;  /// final_local_dynamic_init: error
+  x is Object;   /// final_local_is: error

[eernst, 2017/07/10 16:05:32]

Should get the same treatment as line 17.

+  throw x;   /// final_local_throw: error
+  [x];   /// final_local_literal_list_init: error
+  var m1 = {4: x};   /// final_local_literal_map_value_init: error
+  var m2 = {x : 4};   /// final_local_literal_map_key_init: error
+  Map<dynamic, dynamic> m3 = {4: x};  /// final_local_literal_map_value_init2: error
+  Map<dynamic, dynamic> m4 = {x : 4};  /// final_local_literal_map_key_init2: error
+  x ?? 499;  /// final_local_null_equals2: error
+  null ?? x;  /// final_local_null_equals2: error
+  return x;   /// final_local_return: error
+  while (x) {};  /// final_local_while: error
+  do {} while (x);  /// final_local_do_while: error
+  for (var v in x) {}   /// final_local_for_in: error
+  for (x in [1, 2]) {}  /// final_local_for_in2: ok

[eernst, 2017/07/10 16:05:33]

Why would it be OK to assign to a final local, no matter whether it's void?

+  x += 1;  /// final_local_plus_eq: error
+  x.toString();  /// final_local_toString: error
+  x?.toString();  /// final_local_null_dot: error
+  x..toString();  /// final_local_cascade: error
+}
+
+void global;
+void testVoidGlobal() {
+  global;  /// global_stmt: ok
+  true ? global : global;  /// global_conditional: ok

[eernst, 2017/07/10 16:05:30]

Should get the same treatment as line 11.

+  for (global; false; global) {}   /// global_for: ok
+  use(global);   /// global_argument: error
+  use(global as Object);  /// global_as: error?

[eernst, 2017/07/10 16:05:32]

Should get the same treatment as line 14.

+  void y = global;   /// global_void_init: error
+  dynamic y = global;  /// global_dynamic_init: error
+  global is Object;   /// global_is: error

[eernst, 2017/07/10 16:05:33]

Should get the same treatment as line 17.

+  throw global;   /// global_throw: error
+  [global];   /// global_literal_list_init: error
+  var m1 = {4: global };   /// global_literal_map_value_init: error
+  var m2 = { global: 4};   /// global_literal_map_key_init: error
+  Map<dynamic, dynamic> m3 = {4: global };  /// global_literal_map_value_init2: error
+  Map<dynamic, dynamic> m4 = { global: 4};  /// global_literal_map_key_init2: error
+  null ?? global;  /// global_null_equals2: error
+  global ?? 499;  /// global_null_equals2: error
+  return global;   /// global_return: error
+  while (global) {};  /// global_while: error
+  do {} while (global);  /// global_do_while: error
+  for (var v in global) {}   /// global_for_in: error
+  for (global in [1, 2]) {}  /// global_for_in2: ok
+  global += 1;  /// global_plus_eq: error
+  global.toString();  /// global_toString: error
+  global?.toString();  /// global_null_dot: error
+  global..toString();  /// global_cascade: error
+}
+
+void testVoidConditional() {
+  void x;
+  (true ? x : x);   /// conditional_parens: error

[Leaf, 2017/02/23 21:30:52]

Seems odd to me.  As far as I can find a unifying theme here, it's that you're
not allowed to construct aggregates with void subcomponents, and not assign void
things to other things without an explicit cast.  Parens don't really feel like
either of these.

[eernst, 2017/07/10 16:05:30]

The informal spec allows `(e)` even for void `e`, and I think we agreed on that,
but the conditional should be treated like in line 11.

+  true ? x : x;  /// conditional_stmt: ok

[eernst, 2017/07/10 16:05:30]

Should get the same treatment as line 11.

+  true ? true ? x : x : true ? x : x;  /// conditional_conditional: ok

[eernst, 2017/07/10 16:05:31]

Should get the same treatment as line 11.

+  for (true ? x : x; false; true ? x : x) {}   /// conditional_for: ok

[eernst, 2017/07/10 16:05:32]

Should get the same treatment as line 11.

+  use(true ? x : x);   /// conditional_argument: error
+  void y = true ? x : x;   /// conditional_void_init: error
+  dynamic y = true ? x : x;  /// conditional_dynamic_init: error
+  throw true ? x : x;   /// conditional_throw: error
+  [true ? x : x];   /// conditional_literal_list_init: error
+  var m1 = {4: true ? x : x};   /// conditional_literal_map_value_init: error
+  Map<dynamic, dynamic> m3 = {4: true ? x : x};  /// conditional_literal_map_value_init2: error
+  null ?? true ? x : x;  /// conditional_null_equals2: error
+  return true ? x : x;   /// conditional_return: error
+  while (true ? x : x) {};  /// conditional_while: error
+  do {} while (true ? x : x);  /// conditional_do_while: error
+  for (var v in true ? x : x) {}   /// conditional_for_in: error
+
+  (true ? 499 : x);   /// conditional2_parens: error
+  true ? 499 : x;  /// conditional2_stmt: ok
+  true ? true ? 499 : x : true ? 499 : x;  /// conditional2_conditional: ok

[eernst, 2017/07/10 16:05:30]

Should get the same treatment as line 11.

+  for (true ? 499 : x; false; true ? 499 : x) {}   /// conditional2_for: ok

[eernst, 2017/07/10 16:05:31]

Should get the same treatment as line 11.

+  use(true ? 499 : x);   /// conditional2_argument: error
+  void y = true ? 499 : x;   /// conditional2_void_init: error
+  dynamic y = true ? 499 : x;  /// conditional2_dynamic_init: error
+  throw true ? 499 : x;   /// conditional2_throw: error
+  [true ? 499 : x];   /// conditional2_literal_list_init: error
+  var m1 = {4: true ? 499 : x};   /// conditional2_literal_map_value_init: error
+  Map<dynamic, dynamic> m3 = {4: true ? 499 : x};  /// conditional2_literal_map_value_init2: error
+  null ?? true ? 499 : x;  /// conditional2_null_equals2: error
+  return true ? 499 : x;   /// conditional2_return: error
+  while (true ? 499 : x) {};  /// conditional2while: error
+  do {} while (true ? 499 : x);  /// conditional2do_while: error
+  for (var v in true ? 499 : x) {}   /// conditional2for_in: error
+
+  (true ? x : 499);   /// conditional3_parens: error

[eernst, 2017/07/10 16:05:33]

Should get the same treatment as line 11.

+  true ? x : 499;  /// conditional3_stmt: ok

[eernst, 2017/07/10 16:05:31]

Should get the same treatment as line 11.

+  true ? true ? x : 499 : true ? x : 499;  /// conditional3_conditional: ok

[eernst, 2017/07/10 16:05:33]

Should get the same treatment as line 11.

+  for (true ? x : 499; false; true ? x : 499) {}   /// conditional3_for: ok

[eernst, 2017/07/10 16:05:31]

Should get the same treatment as line 11.

+  use(true ? x : 499);   /// conditional3_argument: error
+  void y = true ? x : 499;   /// conditional3_void_init: error
+  dynamic y = true ? x : 499;  /// conditional3_dynamic_init: error
+  throw true ? x : 499;   /// conditional3_throw: error
+  [true ? x : 499];   /// conditional3_literal_list_init: error
+  var m1 = {4: true ? x : 499 };   /// conditional3_literal_map_value_init: error
+  Map<dynamic, dynamic> m3 = {4: true ? x : 499 };  /// conditional3_literal_map_value_init2: error
+  null ?? true ? x : 499;  /// conditional3_null_equals2: error
+  return true ? x : 499;   /// conditional3_return: error
+  while (true ? x : 499) {};  /// conditional_while: error
+  do {} while (true ? x : 499);  /// conditional_do_while: error
+  for (var v in true ? x : 499) {}   /// conditional_for_in: error
+}
+
+
+class A<T> {
+  T x;
+
+  void foo() {}
+}
+
+class B implements A<void> {

[Leaf, 2017/02/23 21:30:52]

Consider adding the contra-variant parameter case as well?

bar(int x) {}

overriden with

bar(void x) {}

?

+  void x;
+
+  int foo() => 499;
+}
+
+class C implements A<void> {

[Leaf, 2017/02/23 21:30:52]

Is it deliberate that there is an error here (unimplemented foo?)

+  void get x => null;
+  set x(void y) {};
+}
+
+
+void testInstanceField() {
+  A<void> a = new A<void>();
+  a.x = 499;  /// field_assign: ok
+  a.x;  /// instance_stmt: ok
+  true ? a.x : a.x;  /// instance_conditional: ok

[eernst, 2017/07/10 16:05:32]

Should get the same treatment as line 11.

+  for (a.x; false; a.x) {}   /// instance_for: ok
+  use(a.x);   /// instance_argument: error
+  use(a.x as Object);  /// instance_as: error?

[eernst, 2017/07/10 16:05:30]

Should get the same treatment as line 14.

+  void y = a.x;   /// instance_void_init: error
+  dynamic y = a.x;  /// instance_dynamic_init: error
+  a.x is Object;   /// instance_is: error

[eernst, 2017/07/10 16:05:32]

Should get the same treatment as line 17.

+  throw a.x;   /// instance_throw: error
+  [a.x];   /// instance_literal_list_init: error
+  var m1 = {4: a.x};   /// instance_literal_map_value_init: error
+  var m2 = { a.x : 4};   /// instance_literal_map_key_init: error
+  Map<dynamic, dynamic> m3 = {4: a.x};  /// instance_literal_map_value_init2: error
+  Map<dynamic, dynamic> m4 = { a.x : 4};  /// instance_literal_map_key_init2: error
+  null ?? a.x;  /// instance_null_equals2: error
+  a.x ?? 499;  /// instance_null_equals2: error
+  return a.x;   /// instance_return: error
+  while (a.x) {};  /// instance_while: error
+  do {} while (a.x);  /// instance_do_while: error
+  for (var v in a.x) {}   /// instance_for_in: error
+  for (a.x in [1, 2]) {}  /// instance_for_in2: ok
+  a.x += 1;  /// instance_plus_eq: error
+  a.x.toString();  /// instance_toString: error
+  a.x?.toString();  /// instance_null_dot: error
+  a.x..toString();  /// instance_cascade: error
+
+  B b = new B();
+  b.x = 42;   /// field_assign2: ok
+  b.x;  /// instance2_stmt: ok
+  true ? b.x : b.x;  /// instance2_conditional: ok

[eernst, 2017/07/10 16:05:32]

Should get the same treatment as line 11.

+  for (b.x; false; b.x) {}   /// instance2_for: ok
+  use(b.x);   /// instance2_argument: error
+  use(b.x as Object);  /// instance2_as: error?

[eernst, 2017/07/10 16:05:33]

Should get the same treatment as line 14.

+  void y = b.x;   /// instance2_void_init: error
+  dynamic y = b.x;  /// instance2_dynamic_init: error
+  b.x is Object;   /// instance2_is: error

[eernst, 2017/07/10 16:05:30]

Should get the same treatment as line 17.

+  throw b.x;   /// instance2_throw: error
+  [b.x];   /// instance2_literal_list_init: error
+  var m1 = {4: b.x};   /// instance2_literal_map_value_init: error
+  var m2 = { b.x : 4};   /// instance2_literal_map_key_init: error
+  Map<dynamic, dynamic> m3 = {4: b.x};  /// instance2_literal_map_value_init2: error
+  Map<dynamic, dynamic> m4 = { b.x : 4};  /// instance2_literal_map_key_init2: error
+  null ?? b.x;  /// instance2_null_equals2: error
+  b.x ?? 499;  /// instance2_null_equals2: error
+  return b.x;   /// instance2_return: error
+  while (b.x) {};  /// instance2_while: error
+  do {} while (b.x);  /// instance2_do_while: error
+  for (var v in b.x) {}   /// instance2_for_in: error
+  for (b.x in [1, 2]) {}  /// instance2_for_in2: ok
+  b.x += 1;  /// instance2_plus_eq: error
+  b.x.toString();  /// instance2_toString: error
+  b.x?.toString();  /// instance2_null_dot: error
+  b.x..toString();  /// instance2_cascade: error
+
+  C c = new C();
+  c.x = 32;   /// setter_assign: ok
+  c.x;  /// instance3_stmt: ok
+  true ? c.x : c.x;  /// instance3_conditional: ok

[eernst, 2017/07/10 16:05:33]

Should get the same treatment as line 11.

+  for (c.x; false; c.x) {}   /// instance3_for: ok
+  use(c.x);   /// instance3_argument: error
+  use(c.x as Object);  /// instance3_as: error?

[eernst, 2017/07/10 16:05:34]

Should get the same treatment as line 14.

+  void y = c.x;   /// instance3_void_init: error
+  dynamic y = c.x;  /// instance3_dynamic_init: error
+  c.x is Object;   /// instance3_is: error

[eernst, 2017/07/10 16:05:31]

Should get the same treatment as line 17.

+  throw c.x;   /// instance3_throw: error
+  [c.x];   /// instance3_literal_list_init: error
+  var m1 = {4: c.x};   /// instance3_literal_map_value_init: error
+  var m2 = { c.x : 4};   /// instance3_literal_map_key_init: error
+  Map<dynamic, dynamic> m3 = {4: c.x};  /// instance3_literal_map_value_init2: error
+  Map<dynamic, dynamic> m4 = { c.x : 4};  /// instance3_literal_map_key_init2: error
+  null ?? c.x;  /// instance3_null_equals2: error
+  c.x ?? 499;  /// instance3_null_equals2: error
+  return c.x;   /// instance3_return: error
+  while (c.x) {};  /// instance3_while: error
+  do {} while (c.x);  /// instance3_do_while: error
+  for (var v in c.x) {}   /// instance3_for_in: error
+  for (c.x in [1, 2]) {}  /// instance3_for_in2: ok
+  c.x += 1;  /// instance3_plus_eq: error
+  c.x.toString();  /// instance3_toString: error
+  c.x?.toString();  /// instance3_null_dot: error
+  c.x..toString();  /// instance3_cascade: error
+}
+
+void testParenthesized() {
+  void x;
+  (x);  /// paren_stmt: ok
+  true ? (x) : (x);  /// paren_conditional: ok

[eernst, 2017/07/10 16:05:33]

Should get the same treatment as line 11.

+  for ((x); false; (x)) {}   /// paren_for: ok
+  use((x));   /// paren_argument: error
+  use((x) as Object);  /// paren_as: error?

[eernst, 2017/07/10 16:05:32]

Should get the same treatment as line 14.

+  void y = (x);   /// paren_void_init: error
+  dynamic y = (x);  /// paren_dynamic_init: error
+  (x) is Object;   /// paren_is: error

[eernst, 2017/07/10 16:05:31]

Should get the same treatment as line 17.

+  throw (x);   /// paren_throw: error
+  [(x)];   /// paren_literal_list_init: error
+  var m1 = {4: (x) };   /// paren_literal_map_value_init: error
+  var m2 = { (x): 4};   /// paren_literal_map_key_init: error
+  Map<dynamic, dynamic> m3 = {4: (x) };  /// paren_literal_map_value_init2: error
+  Map<dynamic, dynamic> m4 = { (x): 4};  /// paren_literal_map_key_init2: error
+  (x) ?? 499;  /// paren_null_equals2: error
+  null ?? (x);  /// paren_null_equals2: error
+  return (x);   /// paren_return: error
+  while ((x)) {};  /// paren_while: error
+  do {} while ((x));  /// paren_do_while: error
+  for (var v in (x)) {}   /// paren_for_in: error
+  (x).toString();  /// paren_toString: error
+  (x)?.toString();  /// paren_null_dot: error
+  (x)..toString();  /// paren_cascade: error
+}
+
+main() {
+  testVoidParam(499);
+  testVoidCall(() {});
+  testVoidLocal();
+  testVoidFinalLocal();
+  testVoidConditional();
+  testInstanceField();
+  testParenthesized();
+}