pkg/compiler/lib/src/js_emitter/class_stub_generator.dart

// Copyright (c) 2014, 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.

part of dart2js.js_emitter;

class ClassStubGenerator {
  final Namer namer;
  final Compiler compiler;
  final JavaScriptBackend backend;

  ClassStubGenerator(this.compiler, this.namer, this.backend);

  jsAst.Expression generateClassConstructor(ClassElement classElement,
                                            Iterable<String> fields) {
    // TODO(sra): Implement placeholders in VariableDeclaration position:
    //
    //     String constructorName = namer.getNameOfClass(classElement);
    //     return js.statement('function #(#) { #; }',
    //        [ constructorName, fields,
    //            fields.map(
    //                (name) => js('this.# = #', [name, name]))]));
    return js('function(#) { #; }',
        [fields,
         fields.map((name) => js('this.# = #', [name, name]))]);
  }

  jsAst.Expression generateGetter(Element member, String fieldName) {
    ClassElement cls = member.enclosingClass;
    String receiver = backend.isInterceptorClass(cls) ? 'receiver' : 'this';
    List<String> args = backend.isInterceptedMethod(member) ? ['receiver'] : [];
    return js('function(#) { return #.# }', [args, receiver, fieldName]);
  }

  jsAst.Expression generateSetter(Element member, String fieldName) {
    ClassElement cls = member.enclosingClass;
    String receiver = backend.isInterceptorClass(cls) ? 'receiver' : 'this';
    List<String> args = backend.isInterceptedMethod(member) ? ['receiver'] : [];
    // TODO(floitsch): remove 'return'?
    return js('function(#, v) { return #.# = v; }',
        [args, receiver, fieldName]);
  }

  /**
   * Documentation wanted -- johnniwinther
   *
   * Invariant: [member] must be a declaration element.
   */
  Map<String, jsAst.Expression> generateCallStubsForGetter(
      Element member, Set<Selector> selectors) {
    assert(invariant(member, member.isDeclaration));

    // If the method is intercepted, the stub gets the
    // receiver explicitely and we need to pass it to the getter call.
    bool isInterceptedMethod = backend.isInterceptedMethod(member);
    bool isInterceptorClass =
        backend.isInterceptorClass(member.enclosingClass);

    const String receiverArgumentName = r'$receiver';

    jsAst.Expression buildGetter() {
      jsAst.Expression receiver =
          js(isInterceptorClass ? receiverArgumentName : 'this');
      if (member.isGetter) {
        String getterName = namer.getterName(member);
        if (isInterceptedMethod) {
          return js('this.#(#)', [getterName, receiver]);
        }
        return js('#.#()', [receiver, getterName]);
      } else {
        String fieldName = namer.instanceFieldPropertyName(member);
        return js('#.#', [receiver, fieldName]);
      }
    }

    Map<String, jsAst.Expression> generatedStubs = <String, jsAst.Expression>{};

    // Two selectors may match but differ only in type.  To avoid generating
    // identical stubs for each we track untyped selectors which already have
    // stubs.
    Set<Selector> generatedSelectors = new Set<Selector>();
    for (Selector selector in selectors) {
      if (selector.applies(member, compiler.world)) {
        selector = selector.asUntyped;
        if (generatedSelectors.contains(selector)) continue;
        generatedSelectors.add(selector);

        String invocationName = namer.invocationName(selector);
        Selector callSelector = new Selector.callClosureFrom(selector);
        String closureCallName = namer.invocationName(callSelector);

        List<jsAst.Parameter> parameters = <jsAst.Parameter>[];
        List<jsAst.Expression> arguments = <jsAst.Expression>[];
        if (isInterceptedMethod) {
          parameters.add(new jsAst.Parameter(receiverArgumentName));
        }

        for (int i = 0; i < selector.argumentCount; i++) {
          String name = 'arg$i';
          parameters.add(new jsAst.Parameter(name));
          arguments.add(js('#', name));
        }

        jsAst.Fun function = js(
            'function(#) { return #.#(#); }',
            [ parameters, buildGetter(), closureCallName, arguments]);

        generatedStubs[invocationName] = function;
      }
    }

    return generatedStubs;
  }
}