Add compiler error when instantiating abstract class

runtime/vm/object.h

 // 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.
 
 #ifndef VM_OBJECT_H_
 #define VM_OBJECT_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/utils.h"
@@ skipping 630 matching lines @@
 
   static intptr_t InstanceSize() {
     return RoundedAllocationSize(sizeof(RawClass));
   }
 
   bool is_interface() const {
     return InterfaceBit::decode(raw_ptr()->state_bits_);
   }
   void set_is_interface() const;
 
+  bool is_abstract() const {
+    return AbstractBit::decode(raw_ptr()->state_bits_);
+  }
+  void set_is_abstract() const;
+
   bool is_finalized() const {
     return StateBits::decode(raw_ptr()->state_bits_) == RawClass::kFinalized;
   }
   void set_is_finalized() const;
 
   bool is_prefinalized() const {
     return StateBits::decode(raw_ptr()->state_bits_) == RawClass::kPreFinalized;
   }
 
   void set_is_prefinalized() const;
@@ skipping 48 matching lines @@
 
   // Return a class object corresponding to the specified kind. If
   // a canonicalized version of it exists then that object is returned
   // otherwise a new object is allocated and returned.
   static RawClass* GetClass(intptr_t class_id, bool is_signature_class);
 
  private:
   enum {
     kConstBit = 1,
     kInterfaceBit = 2,
-    kStateTagBit = 3,
+    kAbstractBit = 3,
+    kStateTagBit = 4,
     kStateTagSize = 2,
   };
   class ConstBit : public BitField<bool, kConstBit, 1> {};
   class InterfaceBit : public BitField<bool, kInterfaceBit, 1> {};
+  class AbstractBit : public BitField<bool, kAbstractBit, 1> {};
   class StateBits : public BitField<RawClass::ClassState,
                                     kStateTagBit, kStateTagSize> {};  // NOLINT
 
   void set_name(const String& value) const;
   void set_token_pos(intptr_t value) const;
   void set_signature_function(const Function& value) const;
   void set_signature_type(const AbstractType& value) const;
   void set_class_state(RawClass::ClassState state) const;
   void set_state_bits(uint8_t bits) const;
 
@@ skipping 4804 matching lines @@
     if (this->CharAt(i) != str.CharAt(begin_index + i)) {
       return false;
     }
   }
   return true;
 }
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_H_