Type inference for StringConcatenation.

pkg/front_end/lib/src/fasta/kernel/body_builder.dart

 // Copyright (c) 2016, 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.
 
 library fasta.body_builder;
 
 import '../fasta_codes.dart'
     show FastaMessage, codeExpectedButGot, codeExpectedFunctionBody;
 
 import '../parser/parser.dart' show FormalParameterType, optional;
@@ skipping 1008 matching lines @@
         if (expressions == null) {
           expressions = parts.sublist(0, i);
         }
         expressions.addAll(part.expressions);
       } else {
         if (expressions != null) {
           expressions.add(part);
         }
       }
     }
-    push(new StringConcatenation(expressions ?? parts));
+    push(astFactory.stringConcatenation(expressions ?? parts, null));
   }
 
   @override
   void handleLiteralInt(Token token) {
     debugEvent("LiteralInt");
     push(astFactory.intLiteral(int.parse(token.lexeme), token));
   }
 
   @override
   void handleEmptyFunctionBody(Token semicolon) {
@@ skipping 2091 matching lines @@
   } else if (node is PrefixBuilder) {
     return node.name;
   } else if (node is ThisAccessor) {
     return node.isSuper ? "super" : "this";
   } else if (node is FastaAccessor) {
     return node.plainNameForRead;
   } else {
     return internalError("Unhandled: ${node.runtimeType}");
   }
 }