Implement modular compilation

lib/src/codegen/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);
-    return units;
-  }
-
-  @override
-  visitExpression(Expression node) {
-    var coercion = CoercionInfo.get(node);
-    if (coercion is DownCast) {
-      return _visitDownCast(coercion, node);
-    }
-    return super.visitExpression(node);
-  }
-
-  @override
-  visitForEachStatement(ForEachStatement node) {
-    // Visit other children.
-    node.iterable.accept(this);
-    node.body.accept(this);
-
-    // If needed, assert a cast inside the body before the variable is read.
-    var variable = node.identifier ?? node.loopVariable.identifier;
-    var coercion = CoercionInfo.get(variable);
-    if (coercion is DownCast) {
-      // Build the cast. We will place this cast in the body, so need to clone
-      // the variable's AST node and clear out its static type (otherwise we
-      // will optimize away the cast).
-      var cast = _castExpression(
-          _clone(variable)..staticType = DynamicTypeImpl.instance,
-          coercion.convertedType);
-
-      var body = node.body;
-      var blockBody = <Statement>[RawAstBuilder.expressionStatement(cast)];
-      if (body is Block) {
-        blockBody.addAll(body.statements);
-      } else {
-        blockBody.add(body);
-      }
-      _replaceNode(node, body, RawAstBuilder.block(blockBody));
-    }
-  }
-
-  void _visitDownCast(DownCast node, Expression expr) {
-    expr.visitChildren(this);
-    _replaceNode(expr.parent, expr, coerceExpression(expr, node));
-  }
-
-  void _replaceNode(AstNode parent, AstNode oldNode, AstNode newNode) {
-    if (!identical(oldNode, newNode)) {
-      var replaced = parent.accept(new NodeReplacer(oldNode, newNode));
-      // It looks like NodeReplacer will always return true.
-      // It does throw IllegalArgumentException though, if child is not found.
-      assert(replaced);
-    }
-  }
-
-  /// Coerce [e] using [c], returning a new expression.
-  Expression coerceExpression(Expression e, DownCast node) {
-    if (e is NamedExpression) {
-      Expression inner = coerceExpression(e.expression, node);
-      return new NamedExpression(e.name, inner);
-    }
-    return _castExpression(e, node.convertedType);
-  }
-
-  Expression _castExpression(Expression e, DartType toType) {
-    // We use an empty name in the AST, because the JS code generator only cares
-    // about the target type. It does not look at the AST name.
-    var typeName = new TypeName(AstBuilder.identifierFromString(''), null);
-    typeName.type = toType;
-    var cast = AstBuilder.asExpression(e, typeName);
-    cast.staticType = toType;
-    return cast;
-  }
-
-  /*=T*/ _clone/*<T extends AstNode>*/(/*=T*/ node) {
-    var copy = node.accept(cloner);
-    ResolutionCopier.copyResolutionData(node, copy);
-    return copy;
-  }
-}
-
-class _TreeCloner extends analyzer.AstCloner {
-  void _cloneProperties(AstNode clone, AstNode node) {
-    if (clone != null) {
-      CoercionInfo.set(clone, CoercionInfo.get(node));
-      DynamicInvoke.set(clone, DynamicInvoke.get(node));
-    }
-  }
-
-  @override
-  AstNode cloneNode(AstNode node) {
-    var clone = super.cloneNode(node);
-    _cloneProperties(clone, node);
-    return clone;
-  }
-
-  @override
-  List cloneNodeList(List list) {
-    var clone = super.cloneNodeList(list);
-    for (int i = 0, len = list.length; i < len; i++) {
-      _cloneProperties(clone[i], list[i]);
-    }
-    return clone;
-  }
-
-  // TODO(jmesserly): ResolutionCopier is not copying this yet.
-  @override
-  BlockFunctionBody visitBlockFunctionBody(BlockFunctionBody node) {
-    var clone = super.visitBlockFunctionBody(node);
-    (clone as FunctionBodyImpl).localVariableInfo =
-        (node as FunctionBodyImpl).localVariableInfo;
-    return clone;
-  }
-
-  @override
-  ExpressionFunctionBody visitExpressionFunctionBody(
-      ExpressionFunctionBody node) {
-    var clone = super.visitExpressionFunctionBody(node);
-    (clone as FunctionBodyImpl).localVariableInfo =
-        (node as FunctionBodyImpl).localVariableInfo;
-    return clone;
-  }
-}