Support `void` as generic argument.

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
+  for (x; false; x) {}   /// param_for: ok
+  use(x);   /// param_argument: static type warning
+  use(x as Object);  /// param_as: ok
+  void y = x;   /// param_void_init: static type warning
+  dynamic z = x;  /// param_dynamic_init: static type warning
+  x is Object;   /// param_is: static type warning
+  throw x;   /// param_throw: static type warning
+  [x];   /// param_literal_list_init: static type warning
+  var m1 = {4: x};   /// param_literal_map_value_init: static type warning
+  var m2 = {x : 4};   /// param_literal_map_key_init: static type warning
+  Map<dynamic, dynamic> m3 = {4: x};  /// param_literal_map_value_init2: static type warning
+  Map<dynamic, dynamic> m4 = {x : 4};  /// param_literal_map_key_init2: static type warning
+  x ?? 499;  /// param_null_equals2: static type warning
+  null ?? x;  /// param_null_equals2: static type warning
+  return x;   /// param_return: static type warning
+  while (x) {};  /// param_while: static type warning
+  do {} while (x);  /// param_do_while: static type warning
+  for (var v in x) {}   /// param_for_in: static type warning
+  for (x in [1, 2]) {}  /// param_for_in2: ok
+  x += 1;  /// param_plus_eq: static type warning
+  x.toString();  /// param_toString: static type warning
+  x?.toString();  /// param_null_dot: static type warning
+  x..toString();  /// param_cascade: static type warning
+}
+
+void testVoidCall(void f()) {
+  f();  /// call_stmt: ok
+  true ? f() : f();  /// call_conditional: ok
+  for (f(); false; f()) {}   /// call_for: ok
+  use(f());   /// call_argument: static type warning
+  use(f() as Object);  /// call_as: ok
+  void y = f();   /// call_void_init: static type warning
+  dynamic z = f();  /// call_dynamic_init: static type warning
+  f() is Object;   /// call_is: static type warning
+  throw f();   /// call_throw: static type warning
+  [f()];   /// call_literal_list_init: static type warning
+  var m1 = {4: f() };   /// call_literal_map_value_init: static type warning
+  var m2 = { f(): 4};   /// call_literal_map_key_init: static type warning
+  Map<dynamic, dynamic> m3 = {4: f() };  /// call_literal_map_value_init2: static type warning
+  Map<dynamic, dynamic> m4 = { f(): 4};  /// call_literal_map_key_init2: static type warning
+  f() ?? 499;  /// call_null_equals2: static type warning
+  null ?? f();  /// call_null_equals2: static type warning
+  return f();   /// call_return: static type warning
+  while (f()) {};  /// call_while: static type warning
+  do {} while (f());  /// call_do_while: static type warning
+  for (var v in f()) {}   /// call_for_in: static type warning
+  f().toString();  /// call_toString: static type warning
+  f()?.toString();  /// call_null_dot: static type warning
+  f()..toString();  /// call_cascade: static type warning
+}
+
+void testVoidLocal() {
+  void x;
+  x = 42;   /// local_assign: ok
+  x;  /// local_stmt: ok
+  true ? x : x;  /// local_conditional: ok
+  for (x; false; x) {}   /// local_for: ok
+  use(x);   /// local_argument: static type warning
+  use(x as Object);  /// local_as: ok
+  void y = x;   /// local_void_init: static type warning
+  dynamic z = x;  /// local_dynamic_init: static type warning
+  x is Object;   /// local_is: static type warning
+  throw x;   /// local_throw: static type warning
+  [x];   /// local_literal_list_init: static type warning
+  var m1 = {4: x};   /// local_literal_map_value_init: static type warning
+  var m2 = {x : 4};   /// local_literal_map_key_init: static type warning
+  Map<dynamic, dynamic> m3 = {4: x};  /// local_literal_map_value_init2: static type warning
+  Map<dynamic, dynamic> m4 = {x : 4};  /// local_literal_map_key_init2: static type warning
+  x ?? 499;  /// local_null_equals2: static type warning
+  null ?? x;  /// local_null_equals2: static type warning
+  return x;   /// local_return: static type warning
+  while (x) {};  /// local_while: static type warning
+  do {} while (x);  /// local_do_while: static type warning
+  for (var v in x) {}   /// local_for_in: static type warning
+  for (x in [1, 2]) {}  /// local_for_in2: ok
+  x += 1;  /// local_plus_eq: static type warning
+  x.toString();  /// local_toString: static type warning
+  x?.toString();  /// local_null_dot: static type warning
+  x..toString();  /// local_cascade: static type warning
+}
+
+void testVoidFinalLocal() {
+  final void x = null;
+  x = 42;   /// final_local_assign: static type warning
+  x;  /// final_local_stmt: ok
+  true ? x : x;  /// final_local_conditional: ok
+  for (x; false; x) {}   /// final_local_for: ok
+  use(x);   /// final_local_argument: static type warning
+  use(x as Object);  /// final_local_as: ok
+  void y = x;   /// final_local_void_init: static type warning
+  dynamic z = x;  /// final_local_dynamic_init: static type warning
+  x is Object;   /// final_local_is: static type warning
+  throw x;   /// final_local_throw: static type warning
+  [x];   /// final_local_literal_list_init: static type warning
+  var m1 = {4: x};   /// final_local_literal_map_value_init: static type warning
+  var m2 = {x : 4};   /// final_local_literal_map_key_init: static type warning
+  Map<dynamic, dynamic> m3 = {4: x};  /// final_local_literal_map_value_init2: static type warning
+  Map<dynamic, dynamic> m4 = {x : 4};  /// final_local_literal_map_key_init2: static type warning
+  x ?? 499;  /// final_local_null_equals2: static type warning
+  null ?? x;  /// final_local_null_equals2: static type warning
+  return x;   /// final_local_return: static type warning
+  while (x) {};  /// final_local_while: static type warning
+  do {} while (x);  /// final_local_do_while: static type warning
+  for (var v in x) {}   /// final_local_for_in: static type warning
+  for (x in [1, 2]) {}  /// final_local_for_in2: ok
+  x += 1;  /// final_local_plus_eq: static type warning
+  x.toString();  /// final_local_toString: static type warning
+  x?.toString();  /// final_local_null_dot: static type warning
+  x..toString();  /// final_local_cascade: static type warning
+}
+
+void global;
+void testVoidGlobal() {
+  global;  /// global_stmt: ok
+  true ? global : global;  /// global_conditional: ok
+  for (global; false; global) {}   /// global_for: ok
+  use(global);   /// global_argument: static type warning
+  use(global as Object);  /// global_as: ok
+  void y = global;   /// global_void_init: static type warning
+  dynamic z = global;  /// global_dynamic_init: static type warning
+  global is Object;   /// global_is: static type warning
+  throw global;   /// global_throw: static type warning
+  [global];   /// global_literal_list_init: static type warning
+  var m1 = {4: global };   /// global_literal_map_value_init: static type warning
+  var m2 = { global: 4};   /// global_literal_map_key_init: static type warning
+  Map<dynamic, dynamic> m3 = {4: global };  /// global_literal_map_value_init2: static type warning
+  Map<dynamic, dynamic> m4 = { global: 4};  /// global_literal_map_key_init2: static type warning
+  null ?? global;  /// global_null_equals2: static type warning
+  global ?? 499;  /// global_null_equals2: static type warning
+  return global;   /// global_return: static type warning
+  while (global) {};  /// global_while: static type warning
+  do {} while (global);  /// global_do_while: static type warning
+  for (var v in global) {}   /// global_for_in: static type warning
+  for (global in [1, 2]) {}  /// global_for_in2: ok
+  global += 1;  /// global_plus_eq: static type warning
+  global.toString();  /// global_toString: static type warning
+  global?.toString();  /// global_null_dot: static type warning
+  global..toString();  /// global_cascade: static type warning
+}
+
+void testVoidConditional() {
+  void x;
+  (true ? x : x);   /// conditional_parens: static type warning
+  true ? x : x;  /// conditional_stmt: ok
+  true ? true ? x : x : true ? x : x;  /// conditional_conditional: ok
+  for (true ? x : x; false; true ? x : x) {}   /// conditional_for: ok
+  use(true ? x : x);   /// conditional_argument: static type warning
+  void y = true ? x : x;   /// conditional_void_init: static type warning
+  dynamic z = true ? x : x;  /// conditional_dynamic_init: static type warning
+  throw true ? x : x;   /// conditional_throw: static type warning
+  [true ? x : x];   /// conditional_literal_list_init: static type warning
+  var m1 = {4: true ? x : x};   /// conditional_literal_map_value_init: static type warning
+  Map<dynamic, dynamic> m3 = {4: true ? x : x};  /// conditional_literal_map_value_init2: static type warning
+  null ?? true ? x : x;  /// conditional_null_equals2: static type warning
+  return true ? x : x;   /// conditional_return: static type warning
+  while (true ? x : x) {};  /// conditional_while: static type warning
+  do {} while (true ? x : x);  /// conditional_do_while: static type warning
+  for (var v in true ? x : x) {}   /// conditional_for_in: static type warning
+
+  (true ? 499 : x);   /// conditional2_parens: static type warning
+  true ? 499 : x;  /// conditional2_stmt: ok
+  true ? true ? 499 : x : true ? 499 : x;  /// conditional2_conditional: ok
+  for (true ? 499 : x; false; true ? 499 : x) {}   /// conditional2_for: ok
+  use(true ? 499 : x);   /// conditional2_argument: static type warning
+  void y2 = true ? 499 : x;   /// conditional2_void_init: static type warning
+  dynamic z2 = true ? 499 : x;  /// conditional2_dynamic_init: static type warning
+  throw true ? 499 : x;   /// conditional2_throw: static type warning
+  [true ? 499 : x];   /// conditional2_literal_list_init: static type warning
+  var m12 = {4: true ? 499 : x};   /// conditional2_literal_map_value_init: static type warning
+  Map<dynamic, dynamic> m32 = {4: true ? 499 : x};  /// conditional2_literal_map_value_init2: static type warning
+  null ?? true ? 499 : x;  /// conditional2_null_equals2: static type warning
+  return true ? 499 : x;   /// conditional2_return: static type warning
+  while (true ? 499 : x) {};  /// conditional2while: static type warning
+  do {} while (true ? 499 : x);  /// conditional2do_while: static type warning
+  for (var v in true ? 499 : x) {}   /// conditional2for_in: static type warning
+
+  (true ? x : 499);   /// conditional3_parens: static type warning
+  true ? x : 499;  /// conditional3_stmt: ok
+  true ? true ? x : 499 : true ? x : 499;  /// conditional3_conditional: ok
+  for (true ? x : 499; false; true ? x : 499) {}   /// conditional3_for: ok
+  use(true ? x : 499);   /// conditional3_argument: static type warning
+  void y3 = true ? x : 499;   /// conditional3_void_init: static type warning
+  dynamic z3 = true ? x : 499;  /// conditional3_dynamic_init: static type warning
+  throw true ? x : 499;   /// conditional3_throw: static type warning
+  [true ? x : 499];   /// conditional3_literal_list_init: static type warning
+  var m13 = {4: true ? x : 499 };   /// conditional3_literal_map_value_init: static type warning
+  Map<dynamic, dynamic> m33 = {4: true ? x : 499 };  /// conditional3_literal_map_value_init2: static type warning
+  null ?? true ? x : 499;  /// conditional3_null_equals2: static type warning
+  return true ? x : 499;   /// conditional3_return: static type warning
+  while (true ? x : 499) {};  /// conditional_while: static type warning
+  do {} while (true ? x : 499);  /// conditional_do_while: static type warning
+  for (var v in true ? x : 499) {}   /// conditional_for_in: static type warning
+}
+
+
+class A<T> {
+  T x;
+
+  void foo() {}
+}
+
+class B implements A<void> {
+  void x;
+
+  int foo() => 499;
+
+  void forInTest() {
+    for (x in <void>[]) {}  /// instance2_for_in2: static type warning
+    for (x in [1, 2]) {}  /// instance2_for_in3: ok
+  }
+}
+
+class C implements A<void> {
+  void get x => null;
+  set x(void y) {}
+
+  void forInTest() {
+    for (x in <void>[]) {}  /// instance3_for_in2: static type warning
+    for (x in [1, 2]) {}  /// instance3_for_in3: ok
+  }
+}
+
+
+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
+  for (a.x; false; a.x) {}   /// instance_for: ok
+  use(a.x);   /// instance_argument: static type warning
+  use(a.x as Object);  /// instance_as: ok
+  void y = a.x;   /// instance_void_init: static type warning
+  dynamic z = a.x;  /// instance_dynamic_init: static type warning
+  a.x is Object;   /// instance_is: static type warning
+  throw a.x;   /// instance_throw: static type warning
+  [a.x];   /// instance_literal_list_init: static type warning
+  var m1 = {4: a.x};   /// instance_literal_map_value_init: static type warning
+  var m2 = { a.x : 4};   /// instance_literal_map_key_init: static type warning
+  Map<dynamic, dynamic> m3 = {4: a.x};  /// instance_literal_map_value_init2: static type warning
+  Map<dynamic, dynamic> m4 = { a.x : 4};  /// instance_literal_map_key_init2: static type warning
+  null ?? a.x;  /// instance_null_equals2: static type warning
+  a.x ?? 499;  /// instance_null_equals2: static type warning
+  return a.x;   /// instance_return: static type warning
+  while (a.x) {};  /// instance_while: static type warning
+  do {} while (a.x);  /// instance_do_while: static type warning
+  for (var v in a.x) {}   /// instance_for_in: static type warning
+  a.x += 1;  /// instance_plus_eq: static type warning
+  a.x.toString();  /// instance_toString: static type warning
+  a.x?.toString();  /// instance_null_dot: static type warning
+  a.x..toString();  /// instance_cascade: static type warning
+
+  B b = new B();
+  b.x = 42;   /// field_assign2: ok
+  b.x;  /// instance2_stmt: ok
+  true ? b.x : b.x;  /// instance2_conditional: ok
+  for (b.x; false; b.x) {}   /// instance2_for: ok
+  use(b.x);   /// instance2_argument: static type warning
+  use(b.x as Object);  /// instance2_as: ok
+  void y2 = b.x;   /// instance2_void_init: static type warning
+  dynamic z2 = b.x;  /// instance2_dynamic_init: static type warning
+  b.x is Object;   /// instance2_is: static type warning
+  throw b.x;   /// instance2_throw: static type warning
+  [b.x];   /// instance2_literal_list_init: static type warning
+  var m12 = {4: b.x};   /// instance2_literal_map_value_init: static type warning
+  var m22 = { b.x : 4};   /// instance2_literal_map_key_init: static type warning
+  Map<dynamic, dynamic> m32 = {4: b.x};  /// instance2_literal_map_value_init2: static type warning
+  Map<dynamic, dynamic> m42 = { b.x : 4};  /// instance2_literal_map_key_init2: static type warning
+  null ?? b.x;  /// instance2_null_equals2: static type warning
+  b.x ?? 499;  /// instance2_null_equals2: static type warning
+  return b.x;   /// instance2_return: static type warning
+  while (b.x) {};  /// instance2_while: static type warning
+  do {} while (b.x);  /// instance2_do_while: static type warning
+  for (var v in b.x) {}   /// instance2_for_in: static type warning
+  b.forInTest();
+  b.x += 1;  /// instance2_plus_eq: static type warning
+  b.x.toString();  /// instance2_toString: static type warning
+  b.x?.toString();  /// instance2_null_dot: static type warning
+  b.x..toString();  /// instance2_cascade: static type warning
+
+  C c = new C();
+  c.x = 32;   /// setter_assign: ok
+  c.x;  /// instance3_stmt: ok
+  true ? c.x : c.x;  /// instance3_conditional: ok
+  for (c.x; false; c.x) {}   /// instance3_for: ok
+  use(c.x);   /// instance3_argument: static type warning
+  use(c.x as Object);  /// instance3_as: ok
+  void y3 = c.x;   /// instance3_void_init: static type warning
+  dynamic z3 = c.x;  /// instance3_dynamic_init: static type warning
+  c.x is Object;   /// instance3_is: static type warning
+  throw c.x;   /// instance3_throw: static type warning
+  [c.x];   /// instance3_literal_list_init: static type warning
+  var m13 = {4: c.x};   /// instance3_literal_map_value_init: static type warning
+  var m23 = { c.x : 4};   /// instance3_literal_map_key_init: static type warning
+  Map<dynamic, dynamic> m33 = {4: c.x};  /// instance3_literal_map_value_init2: static type warning
+  Map<dynamic, dynamic> m43 = { c.x : 4};  /// instance3_literal_map_key_init2: static type warning
+  null ?? c.x;  /// instance3_null_equals2: static type warning
+  c.x ?? 499;  /// instance3_null_equals2: static type warning
+  return c.x;   /// instance3_return: static type warning
+  while (c.x) {};  /// instance3_while: static type warning
+  do {} while (c.x);  /// instance3_do_while: static type warning
+  for (var v in c.x) {}   /// instance3_for_in: static type warning
+  c.forInTest();
+  c.x += 1;  /// instance3_plus_eq: static type warning
+  c.x.toString();  /// instance3_toString: static type warning
+  c.x?.toString();  /// instance3_null_dot: static type warning
+  c.x..toString();  /// instance3_cascade: static type warning
+}
+
+void testParenthesized() {
+  void x;
+  (x);  /// paren_stmt: ok
+  true ? (x) : (x);  /// paren_conditional: ok
+  for ((x); false; (x)) {}   /// paren_for: ok
+  use((x));   /// paren_argument: static type warning
+  use((x) as Object);  /// paren_as: ok
+  void y = (x);   /// paren_void_init: static type warning
+  dynamic z = (x);  /// paren_dynamic_init: static type warning
+  (x) is Object;   /// paren_is: static type warning
+  throw (x);   /// paren_throw: static type warning
+  [(x)];   /// paren_literal_list_init: static type warning
+  var m1 = {4: (x) };   /// paren_literal_map_value_init: static type warning
+  var m2 = { (x): 4};   /// paren_literal_map_key_init: static type warning
+  Map<dynamic, dynamic> m3 = {4: (x) };  /// paren_literal_map_value_init2: static type warning
+  Map<dynamic, dynamic> m4 = { (x): 4};  /// paren_literal_map_key_init2: static type warning
+  (x) ?? 499;  /// paren_null_equals2: static type warning
+  null ?? (x);  /// paren_null_equals2: static type warning
+  return (x);   /// paren_return: static type warning
+  while ((x)) {};  /// paren_while: static type warning
+  do {} while ((x));  /// paren_do_while: static type warning
+  for (var v in (x)) {}   /// paren_for_in: static type warning
+  (x).toString();  /// paren_toString: static type warning
+  (x)?.toString();  /// paren_null_dot: static type warning
+  (x)..toString();  /// paren_cascade: static type warning
+}
+
+main() {
+  try {
+    testVoidParam(499);
+    testVoidCall(() {});
+    testVoidLocal();
+    testVoidFinalLocal();
+    testVoidConditional();
+    testInstanceField();
+    testParenthesized();
+  } catch (e) {
+    // Silently eat all dynamic errors.
+    // This test is only testing static warnings.
+  }
+}