Support for removing empty statements (dartbug.com/16810).

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/parser.dart';
@@ skipping 119 matching lines @@
     checkForErrors();
 
     var node = parse(kind, startToken);
     checkForErrors();
 
     var formatter = new SourceVisitor(options, lineInfo, source, selection);
     node.accept(formatter);
 
     var formattedSource = formatter.writer.toString();
 
-    checkTokenStreams(startToken, tokenize(formattedSource));
+    checkTokenStreams(startToken, tokenize(formattedSource),
+                      allowTransforms: options.codeTransforms);
 
     return new FormattedSource(formattedSource, formatter.selection);
   }
 
-  checkTokenStreams(Token t1, Token t2) =>
-      new TokenStreamComparator(lineInfo, t1, t2).verifyEquals();
+  checkTokenStreams(Token t1, Token t2, {allowTransforms: false}) =>
+      new TokenStreamComparator(lineInfo, t1, t2, transforms: allowTransforms).
+          verifyEquals();
 
   ASTNode parse(CodeKind kind, Token start) {
 
     var parser = new Parser(null, this);
 
     switch (kind) {
       case CodeKind.COMPILATION_UNIT:
         return parser.parseCompilationUnit(start);
       case CodeKind.STATEMENT:
         return parser.parseStatement(start);
@@ skipping 21 matching lines @@
   }
 
 }
 
 
 // Compares two token streams.  Used for sanity checking formatted results.
 class TokenStreamComparator {
 
   final LineInfo lineInfo;
   Token token1, token2;
+  bool allowTransforms;
 
-  TokenStreamComparator(this.lineInfo, this.token1, this.token2);
+  TokenStreamComparator(this.lineInfo, this.token1, this.token2,
+      {transforms: false}) : this.allowTransforms = transforms;
 
   /// Verify that these two token streams are equal.
   verifyEquals() {
     while (!isEOF(token1)) {
       checkPrecedingComments();
       if (!checkTokens()) {
         throwNotEqualException(token1, token2);
       }
       advance();
 
@@ skipping 67 matching lines @@
       }
     }
     // Cons(){} => Cons();
     if (isOPEN_CURLY_BRACKET(token1) && isCLOSE_CURLY_BRACKET(token1.next)) {
       if (isSEMICOLON(token2)) {
         token1 = token1.next;
         advance();
         return true;
       }
     }
-    // Advance past synthetic { } tokens
-    if (isOPEN_CURLY_BRACKET(token2) || isCLOSE_CURLY_BRACKET(token2)) {
-      token2 = token2.next;
-      return checkTokens();
+
+    // Transform-related special casing
+    if (allowTransforms) {
+
+      // Advance past empty statements
+      if (isSEMICOLON(token1)) {
+        // TODO whitelist
+        token1 = token1.next;
+        return checkTokens();
+      }
+
+      // Advance past synthetic { } tokens
+      if (isOPEN_CURLY_BRACKET(token2) || isCLOSE_CURLY_BRACKET(token2)) {
+        token2 = token2.next;
+        return checkTokens();
+      }
+
     }
 
     return false;
   }
 
 }
 
 // Cached parser for testing token types.
 final tokenTester = new Parser(null,null);
 
@@ skipping 424 matching lines @@
 
   visitDoubleLiteral(DoubleLiteral node) {
     token(node.literal);
   }
 
   visitEmptyFunctionBody(EmptyFunctionBody node) {
     token(node.semicolon);
   }
 
   visitEmptyStatement(EmptyStatement node) {
-    token(node.semicolon);
+    if (!codeTransforms || node.parent is! Block) {
+      token(node.semicolon);
+    }
   }
 
   visitExportDirective(ExportDirective node) {
     visitNodes(node.metadata, followedBy: newlines);
     token(node.keyword);
     space();
     visit(node.uri);
     allowContinuedLines((){
       visitNodes(node.combinators, precededBy: space, separatedBy: space);
     });
@@ skipping 997 matching lines @@
     var lastLine =
         lineInfo.getLocation(lastOffset).lineNumber;
     var currentLine =
         lineInfo.getLocation(currentOffset).lineNumber;
     return currentLine - lastLine;
   }
 
   String toString() => writer.toString();
 
 }