Add JSNull, JSBool and JSFunction, and move toString into the new interceptor scheme.

sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart

 // Copyright (c) 2012, 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 js_backend;
 
 /**
  * A function element that represents a closure call. The signature is copied
  * from the given element.
  */
@@ skipping 1164 matching lines @@
     // if they share methods with the same signature. Currently we do this only
     // if there are no optional parameters. Closures with optional parameters
     // are more difficult to canonicalize because they would need to have the
     // same default values.
 
     bool hasOptionalParameters = member.optionalParameterCount(compiler) != 0;
     int parameterCount = member.parameterCount(compiler);
 
     Map<int, String> cache;
     String extraArg;
-    String extraArgWithThis;
     String extraArgWithoutComma;
     // Methods on foreign classes take an extra parameter, which is
     // the actual receiver of the call.
     JavaScriptBackend backend = compiler.backend;
     if (backend.isInterceptorClass(member.getEnclosingClass())) {
       cache = interceptorClosureCache;
       extraArg = 'receiver, ';
-      extraArgWithThis = 'this.receiver, ';
       extraArgWithoutComma = 'receiver';
     } else {
       cache = boundClosureCache;
       extraArg = '';
       extraArgWithoutComma = '';
-      extraArgWithThis = '';
     }
 
     String closureClass =
         hasOptionalParameters ? null : cache[parameterCount];
     if (closureClass == null) {
       // Either the class was not cached yet, or there are optional parameters.
       // Create a new closure class.
       SourceString name = const SourceString("BoundClosure");
       ClassElement closureClassElement = new ClosureClassElement(
           name, compiler, member, member.getCompilationUnit());
@@ skipping 13 matching lines @@
           new ClosureInvocationElement(namer.CLOSURE_INVOCATION_NAME, member);
 
       String invocationName = namer.instanceMethodName(callElement);
       List<String> arguments = new List<String>(parameterCount);
       for (int i = 0; i < parameterCount; i++) {
         arguments[i] = "p$i";
       }
       String joinedArgs = Strings.join(arguments, ", ");
       boundClosureBuffer.add(
           "$invocationName: function($joinedArgs) {");
-      boundClosureBuffer.add(
-          " return this.self[this.target]($extraArgWithThis$joinedArgs);");
+      String callArgs = extraArg.isEmpty
+          ? joinedArgs
+          : joinedArgs.isEmpty
+              ? 'this.$extraArgWithoutComma'
+              : 'this.$extraArg$joinedArgs';

[Johnni Winther, 2012/11/20 09:26:20]

Why the 'this.' prefix? 

[ngeoffray, 2012/11/20 10:30:50]

Because you're using a field of the bound closure, which is the actual receiver
of the method. For example:

var c = a.toString;
c();

The call to 'c' does not pass 'a', so when creating the bound closure for
'a.toString', you assign 'a' to a field of the bound closure. Then, when you
call the toString method you basically do:
this.self['toString'](this.receiver);

+      boundClosureBuffer.add(" return this.self[this.target]($callArgs);");

[Johnni Winther, 2012/11/20 09:26:20]

If extraArgWithoutComma is '' then callArgs becomes 'this.'. Is that
intentional?

[ngeoffray, 2012/11/20 10:30:50]

If extraArgWithoutComma is '', then extrArg is ''. Which makes callArlgs be
joinedArgs and not contain extraArgWithoutComma.

[karlklose, 2012/11/20 10:31:00]

I don't think this can happen, because extraArgWithoutComma.isEmpty ->
extraArg.isEmpty by ll. 1189-1197 and that implies callArs == joimedArgs bu l.
1231.

However, this code is really a bit complex. Can you perhaps calculate two flags
in around l. 1190 and use them down here? 

[ngeoffray, 2012/11/20 10:36:21]

I added one flag: hasExtraArgument. What other flag did upi have in mind?

[karlklose, 2012/11/20 14:06:23]

I thought about isInterceptor and hasArguments, but you could as well test for
joinedArguments.isEmpty.

       boundClosureBuffer.add(" }");
       addParameterStubs(callElement, (String stubName, CodeBuffer memberValue) {
         boundClosureBuffer.add(',\n $stubName: $memberValue');
       });
       boundClosureBuffer.add("\n};\n");
 
       closureClass = namer.isolateAccess(closureClassElement);
 
       // Cache it.
       if (!hasOptionalParameters) {
@@ skipping 486 matching lines @@
 const String HOOKS_API_USAGE = """
 // Generated by dart2js, the Dart to JavaScript compiler.
 // The code supports the following hooks:
 // dartPrint(message)   - if this function is defined it is called
 //                        instead of the Dart [print] method.
 // dartMainRunner(main) - if this function is defined, the Dart [main]
 //                        method will not be invoked directly.
 //                        Instead, a closure that will invoke [main] is
 //                        passed to [dartMainRunner].
 """;