Empty map formatting fix (dartbug.com/16382).

pkg/analyzer/lib/src/services/formatter_impl.dart

 // Copyright (c) 2013, 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 formatter_impl;
 
 import 'dart:math';
 
 import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/src/generated/java_core.dart' show CharSequence;
@@ skipping 984 matching lines @@
     visitCommaSeparatedNodes(node.elements /*, followedBy: breakableSpace*/);
     optionalTrailingComma(node.rightBracket);
     unindent();
     token(node.rightBracket);
   }
 
   visitMapLiteral(MapLiteral node) {
     modifier(node.constKeyword);
     visitNode(node.typeArguments, followedBy: space);
     token(node.leftBracket);
-    newlines();
-    indent();
-    visitCommaSeparatedNodes(node.entries, followedBy: newlines);
-    optionalTrailingComma(node.rightBracket);
-    unindent();
-    newlines();
+    if (!node.entries.isEmpty) {
+      newlines();
+      indent();
+      visitCommaSeparatedNodes(node.entries, followedBy: newlines);
+      optionalTrailingComma(node.rightBracket);
+      unindent();
+      newlines();
+    }
     token(node.rightBracket);
   }
 
   visitMapLiteralEntry(MapLiteralEntry node) {
     visit(node.key);
     token(node.separator);
     space();
     visit(node.value);
   }
 
@@ skipping 663 matching lines @@
     var lastLine =
         lineInfo.getLocation(lastOffset).lineNumber;
     var currentLine =
         lineInfo.getLocation(currentOffset).lineNumber;
     return currentLine - lastLine;
   }
 
   String toString() => writer.toString();
 
 }