Fixes #179 -- compile error if editing files during server mode

lib/src/codegen/dart_codegen.dart

 // Copyright (c) 2015, 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 dev_compiler.src.codegen.dart_codegen;
 
 import 'dart:io' show File;
 
 import 'package:analyzer/analyzer.dart' as analyzer;
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
 import 'package:analyzer/src/generated/java_core.dart' as java_core;
 import 'package:analyzer/src/generated/scanner.dart' show Token;
 import 'package:dart_style/dart_style.dart';
 import 'package:logging/logging.dart' as logger;
 import 'package:path/path.dart' as path;
 
+import 'package:dev_compiler/devc.dart' show AbstractCompiler;
 import 'package:dev_compiler/src/info.dart';
-import 'package:dev_compiler/src/checker/rules.dart';
 import 'package:dev_compiler/src/options.dart';
 import 'package:dev_compiler/src/utils.dart' as utils;
 import 'ast_builder.dart';
 import 'code_generator.dart' as codegenerator;
 import 'reify_coercions.dart'
     show CoercionReifier, NewTypeIdDesc, InstrumentedRuntime;
 
 final _log = new logger.Logger('dev_compiler.dart_codegen');
 
 class DevCompilerRuntime extends InstrumentedRuntime {
@@ skipping 348 matching lines @@
     output(id.name);
     return null;
   }
 
   void generate() {
     visitCompilationUnit(unit);
   }
 }
 
 class DartGenerator extends codegenerator.CodeGenerator {
-  final CompilerOptions options;
-  TypeRules _rules;
   final DevCompilerRuntime _runtime = new DevCompilerRuntime();
 
-  DartGenerator(String outDir, Uri root, TypeRules rules, this.options)
-      : _rules = rules,
-        super(outDir, root, rules);
+  DartGenerator(AbstractCompiler compiler) : super(compiler);
 
   Set<LibraryElement> computeExtraImports(Map<Identifier, NewTypeIdDesc> ids) {
     var imports = new Set<LibraryElement>();
     void process(Identifier id, NewTypeIdDesc desc) {
       if (_identifierNeedsQualification(id, desc)) {
         var library = desc.importedFrom;
         if (utils.isDartPrivateLibrary(library)) {
           _log.severe("Dropping import of private library ${library}\n");
           return;
         }
         imports.add(library);
       }
     }
     ids.forEach(process);
     return imports;
   }
 
   String generateLibrary(LibraryUnit library, LibraryInfo info) {
-    var r = new CoercionReifier(library, rules, options, _runtime);
+    var r = new CoercionReifier(library, compiler, _runtime);
     var ids = r.reify();
     var extraImports = computeExtraImports(ids);
 
     for (var unit in library.partsThenLibrary) {
       var libraryDir = makeOutputDirectory(info, unit);
       var uri = unit.element.source.uri;
       _log.fine("Generating unit $uri");
       FileWriter out = new FileWriter(
           options, path.join(libraryDir, '${uri.pathSegments.last}'));
       var unitGen =
@@ skipping 17 matching lines @@
   void output(String s) => _out.print(s);
   void outputln(String s) => _out.println(s);
 
   void generate() {
     unit.visitChildren(this);
   }
 }
 
 // This class emits the code unchanged, for comparison purposes.
 class EmptyDartGenerator extends codegenerator.CodeGenerator {
-  final CompilerOptions options;
-
-  EmptyDartGenerator(String outDir, Uri root, TypeRules rules, this.options)
-      : super(outDir, root, rules);
+  EmptyDartGenerator(AbstractCompiler compiler) : super(compiler);
 
   String generateLibrary(LibraryUnit library, LibraryInfo info) {
     for (var unit in library.partsThenLibrary) {
       var outputDir = makeOutputDirectory(info, unit);
       generateUnit(unit, info, outputDir);
     }
     return null;
   }
 
   void generateUnit(CompilationUnit unit, LibraryInfo info, String libraryDir) {
     var uri = unit.element.source.uri;
     _log.fine("Emitting original unit " + uri.toString());
     FileWriter out = new FileWriter(
         options, path.join(libraryDir, '${uri.pathSegments.last}'));
     var unitGen = new EmptyUnitGenerator(unit, out);
     unitGen.generate();
     out.finalize();
   }
 }