Stub implementation of patch invariants for the patch refactoring.

lib/compiler/implementation/ssa/nodes.dart

 // 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.
 
 abstract class HVisitor<R> {
   R visitAdd(HAdd node);
   R visitBailoutTarget(HBailoutTarget node);
   R visitBitAnd(HBitAnd node);
   R visitBitNot(HBitNot node);
   R visitBitOr(HBitOr node);
@@ skipping 2349 matching lines @@
 
 class HThrow extends HControlFlow {
   final bool isRethrow;
   HThrow(value, [this.isRethrow = false]) : super(<HInstruction>[value]);
   toString() => 'throw';
   accept(HVisitor visitor) => visitor.visitThrow(this);
 }
 
 class HStatic extends HInstruction {
   final Element element;
-  HStatic(this.element) : super(<HInstruction>[]) { assert(element !== null); }
+  HStatic(this.element) : super(<HInstruction>[]) {
+    assert(element !== null);
+    assert(element.isDeclaration);
+  }
 
   void prepareGvn(HTypeMap types) {
     if (!element.isAssignable()) {
       clearAllSideEffects();
       setUseGvn();
     }
   }
   toString() => 'static ${element.name}';
   accept(HVisitor visitor) => visitor.visitStatic(this);
 
@@ skipping 516 matching lines @@
   HBasicBlock get start => expression.start;
   HBasicBlock get end {
     // We don't create a switch block if there are no cases.
     assert(!statements.isEmpty());
     return statements.last().end;
   }
 
   bool accept(HStatementInformationVisitor visitor) =>
       visitor.visitSwitchInfo(this);
 }