Class fields cannot be declared to be of type void

runtime/vm/parser.cc

 // Copyright (c) 2012, 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.
 
 #include "vm/parser.h"
 #include "vm/flags.h"
 
 #ifndef DART_PRECOMPILED_RUNTIME
 
 #include "lib/invocation_mirror.h"
@@ skipping 4477 matching lines @@
       // const fields are implicitly final.
       member.has_final = true;
     }
     if (member.type == NULL) {
       if (member.has_final) {
         member.type = &Object::dynamic_type();
       } else {
         ReportError("missing 'var', 'final', 'const' or type"
                     " in field declaration");
       }
+    } else if (member.type->IsVoidType()) {
+      ReportError(member.name_pos, "field may not be 'void'");

[rmacnak, 2016/08/15 23:55:58]

Would be nice if top level fields gave the same error message.

     }
     ParseFieldDefinition(members, &member);
   } else {
     UnexpectedToken();
   }
   current_member_ = NULL;
   CheckMemberNameConflict(members, &member);
   members->AddMember(member);
 }
 
@@ skipping 10273 matching lines @@
     const ArgumentListNode& function_args,
     const LocalVariable* temp_for_last_arg,
     bool is_super_invocation) {
   UNREACHABLE();
   return NULL;
 }
 
 }  // namespace dart
 
 #endif  // DART_PRECOMPILED_RUNTIME