Implement type inference for PropertySet.

pkg/front_end/lib/src/fasta/testing/validating_instrumentation.dart

 // Copyright (c) 2017, 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.md file.
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 
 import 'package:front_end/src/base/instrumentation.dart';
 import 'package:front_end/src/fasta/messages.dart';
 import 'package:front_end/src/fasta/scanner.dart';
@@ skipping 59 matching lines @@
               'got nothing',
               new _Fix(
                   expectation.commentOffset, expectation.commentLength, ''));
         }
       });
     });
   }
 
   /// Updates the source file at [uri] based on the actual property/value
   /// pairs that were observed.
-  Future<Null> fixSource(Uri uri) async {
+  Future<Null> fixSource(Uri uri, bool offsetsCountCharacters) async {
     var fixes = _fixes[uri];
     if (fixes == null) return;
     File file = new File.fromUri(uri);
     var bytes = (await file.readAsBytes()).toList();
+    int convertOffset(int offset) {
+      if (offsetsCountCharacters) {
+        return UTF8.encode(UTF8.decode(bytes).substring(0, offset)).length;
+      } else {
+        return offset;
+      }
+    }
+
     // Apply the fixes in reverse order so that offsets don't need to be
     // adjusted after each fix.
     fixes.sort((a, b) => b.offset.compareTo(a.offset));
     for (var fix in fixes) {
-      bytes.replaceRange(
-          fix.offset, fix.offset + fix.length, UTF8.encode(fix.replacement));
+      bytes.replaceRange(convertOffset(fix.offset),
+          convertOffset(fix.offset + fix.length), UTF8.encode(fix.replacement));
     }
     await file.writeAsBytes(bytes);
   }
 
   /// Loads expectations from the source file located at [uri].
   ///
   /// Should be called before [finish].
   Future<Null> loadExpectations(Uri uri) async {
     var bytes = await readBytesFromFile(uri);
     var expectations = _unsatisfiedExpectations.putIfAbsent(uri, () => {});
@@ skipping 126 matching lines @@
       this.property, this.value, this.commentOffset, this.commentLength);
 }
 
 class _Fix {
   final int offset;
   final int length;
   final String replacement;
 
   _Fix(this.offset, this.length, this.replacement);
 }