Manually check if a constructor has no body in the backend: either ends with ';', or has not statem…

lib/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.
 
 class Interceptors {
   Compiler compiler;
   Interceptors(Compiler this.compiler);
 
   SourceString mapOperatorToMethodName(Operator op) {
     String name = op.source.stringValue;
@@ skipping 799 matching lines @@
   /**
    * Returns the constructor body associated with the given constructor or
    * creates a new constructor body, if none can be found.
    *
    * Returns [:null:] if the constructor does not have a body.
    */
   ConstructorBodyElement getConstructorBody(FunctionElement constructor) {
     assert(constructor.kind === ElementKind.GENERATIVE_CONSTRUCTOR);
     if (constructor is SynthesizedConstructorElement) return null;
     FunctionExpression node = constructor.parseNode(compiler);
-    if (!node.hasBody()) return null;
+    // If we know the body doesn't have any code, we don't generate
+    // it.
+    if (node.body.asBlock() !== null) {
+      NodeList statements = node.body.asBlock().statements;
+      if (statements.isEmpty()) return null;
+    }
     ClassElement classElement = constructor.enclosingElement;
     ConstructorBodyElement bodyElement;
     for (Link<Element> backendMembers = classElement.backendMembers;
          !backendMembers.isEmpty();
          backendMembers = backendMembers.tail) {
       Element backendMember = backendMembers.head;
       if (backendMember.kind == ElementKind.GENERATIVE_CONSTRUCTOR_BODY) {
         ConstructorBodyElement body = backendMember;
         if (body.constructor == constructor) {
           bodyElement = backendMember;
@@ skipping 2480 matching lines @@
                                    <HInstruction>[target, input],
                                    HType.STRING));
     return builder.pop();
   }
 
   HInstruction result() {
     flushLiterals();
     return prefix;
   }
 }