Add a check for issue 6530, so that we don't report errors in checked mode on a void return type.

sdk/lib/_internal/compiler/implementation/ssa/builder.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.
 
 part of ssa;
 
 class Interceptors {
   Compiler compiler;
   Interceptors(Compiler this.compiler);
 
@@ skipping 3441 matching lines @@
     if (node.isRedirectingFactoryBody) {
       compiler.internalError("Unimplemented: Redirecting factory constructor",
                              node: node);
     }
     HInstruction value;
     if (node.expression == null) {
       value = graph.addConstantNull(constantSystem);
     } else {
       visit(node.expression);
       value = pop();
-      value = potentiallyCheckType(value, returnType);
+      if (returnType == compiler.types.voidType
+          && value is HForeign) {
+        // TODO(6530): remove this check.
+      } else {
+        value = potentiallyCheckType(value, returnType);
+      }
     }
     if (!inliningStack.isEmpty) {
       localsHandler.updateLocal(returnElement, value);
     } else {
       close(attachPosition(new HReturn(value), node)).addSuccessor(graph.exit);
     }
   }
 
   visitThrow(Throw node) {
     if (node.expression == null) {
@@ skipping 1202 matching lines @@
           new HSubGraphBlockInformation(elseBranch.graph));
 
     HBasicBlock conditionStartBlock = conditionBranch.block;
     conditionStartBlock.setBlockFlow(info, joinBlock);
     SubGraph conditionGraph = conditionBranch.graph;
     HIf branch = conditionGraph.end.last;
     assert(branch is HIf);
     branch.blockInformation = conditionStartBlock.blockFlow;
   }
 }