Implement modular compilation

lib/src/compiler/reify_coercions.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.
 
 import 'package:analyzer/analyzer.dart' as analyzer;
 import 'package:analyzer/dart/ast/ast.dart';
-import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/src/dart/ast/ast.dart' show FunctionBodyImpl;
 import 'package:analyzer/src/dart/ast/utilities.dart' show NodeReplacer;
 import 'package:analyzer/src/dart/element/type.dart' show DynamicTypeImpl;
 import 'package:analyzer/src/generated/parser.dart' show ResolutionCopier;
 import 'package:analyzer/src/task/strong/info.dart';
 import 'package:logging/logging.dart' as logger;
 
 import 'ast_builder.dart';
 
 final _log = new logger.Logger('dev_compiler.reify_coercions');
 
-class NewTypeIdDesc {
-  /// If null, then this is not a library level identifier (i.e. it's
-  /// a type parameter, or a special type like void, dynamic, etc)
-  LibraryElement importedFrom;
-
-  /// True => use/def in same library
-  bool fromCurrent;
-
-  /// True => not a source variable
-  bool synthetic;
-  NewTypeIdDesc({this.fromCurrent, this.importedFrom, this.synthetic});
-}
-
 // This class implements a pass which modifies (in place) the ast replacing
 // abstract coercion nodes with their dart implementations.
 class CoercionReifier extends analyzer.GeneralizingAstVisitor<Object> {
   final cloner = new _TreeCloner();
 
-  /// Makes coercions explicit in the resolved AST, and returns the new AST.
-  ///
-  /// This should be the entry point for this class.
-  /// Entering via the visit functions directly will incorrectly mutate the AST.
-  ///
-  /// Returns the new compilation units.
-  List<CompilationUnit> reify(List<CompilationUnit> units) {
-    // Copy the AST before modifying it.
-    units = units.map(_clone).toList();
-    // Visit the AST and make coercions explicit.
-    units.forEach(visitCompilationUnit);
+  CoercionReifier._();
+
+  /// Transforms the given compilation units, and returns a new AST with
+  /// explicit coercion nodes in appropriate places.
+  static List<CompilationUnit> reify(List<CompilationUnit> units) {
+    var cr = new CoercionReifier._();
+    // Clone compilation units, so we don't modify the originals.
+    units = units.map(cr._clone).toList(growable: false);
+    units.forEach(cr.visitCompilationUnit);
     return units;
   }
 
   @override
   visitExpression(Expression node) {
     var coercion = CoercionInfo.get(node);
     if (coercion is DownCast) {
       return _visitDownCast(coercion, node);
     }
     return super.visitExpression(node);
@@ skipping 102 matching lines @@
 
   @override
   ExpressionFunctionBody visitExpressionFunctionBody(
       ExpressionFunctionBody node) {
     var clone = super.visitExpressionFunctionBody(node);
     (clone as FunctionBodyImpl).localVariableInfo =
         (node as FunctionBodyImpl).localVariableInfo;
     return clone;
   }
 }