Use interceptors to handle runtime types.

dart/sdk/lib/_internal/lib/js_types.dart

+// Copyright (c) 2013, 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 _interceptors;
+
+class JsType {}
+
+/**
+ * Interceptor for JavaScript constructor functions that create Dart

[ngeoffray, 2013/09/06 06:54:06]

What is a JavaScript constructor function? Something that we generate? IS that
*the* constructor dart2js creates for each class?

[ahe, 2013/09/09 11:26:29]

Done.

+ * objects. This is used for a variety of things, such as reflection and
+ * runtime types.
+ */
+class JsRuntimeType extends Interceptor implements JsType {
+  const JsRuntimeType();
+
+  String get mangledName => JS('String', r'#.builtin$cls', this);
+
+  String get name {
+    String m = mangledName;
+    String n = unmangleGlobalNameIfPreservedAnyways(m);
+    return n == null ? m : n;
+  }
+
+  String toString() => "JsRuntimeType on '$name'";
+}
+
+/**
+ * Interceptor for JavaScript objects that represent function types.

[ngeoffray, 2013/09/06 06:54:06]

Where do these JavaScript objects come from?

[ahe, 2013/09/09 11:26:29]

Done.

+ */
+// TODO(ahe): Shouldn't use interceptors for this, instead create a constant.

[ngeoffray, 2013/09/06 06:54:06]

What's "this"? How can you make it a constant?

[ahe, 2013/09/09 11:26:29]

Done.

+class JsFunctionType extends Interceptor implements JsType {
+  const JsFunctionType();
+
+  bool get hasReturnType => JS('bool', '"ret" in #', this);

[ngeoffray, 2013/09/06 06:54:06]

Maybe add a helper method hasPropertyIn(String prop, object) => JS(bool, "# in
#", prop, object).

[ahe, 2013/09/09 11:26:29]

I hope to be able to clean this up in a more fundamental way. Additional
abstractions would feel like a step in the wrong direction to me.

+  get returnType => JS('', '#.ret', this);
+
+  bool get isVoid => JS('bool', '!!#.void', this);

[ngeoffray, 2013/09/06 06:54:06]

Will that work on the Android browser?

[ahe, 2013/09/09 11:26:29]

I think it will now.

+
+  bool get hasArguments => JS('bool', '"args" in #', this);
+  List get arguments => JS('JSExtendableArray', '#.args', this);
+
+  bool get hasOptionalArguments => JS('bool', '"opt" in #', this);
+  List get optionalArguments => JS('JSExtendableArray', '#.opt', this);
+
+  bool get hasNamedArguments => JS('bool', '"named" in #', this);
+  get namedArguments => JS('=Object', '#.named', this);
+
+  String toString() {
+    var s = '(';
+    var sep = '';
+    if (hasArguments) {
+      for (var argument in arguments) {
+        s = '$s$sep${runtimeTypeToString(argument)}';
+        sep = ', ';
+      }
+    }
+    if (hasOptionalArguments) {
+      s = '$s$sep[';
+      sep = '';
+      for (var argument in optionalArguments) {
+        s = '$s$sep${runtimeTypeToString(argument)}';
+        sep = ', ';
+      }
+      s = '$s]';
+    }
+    if (hasNamedArguments) {
+      s = '${s}$sep{';
+      sep = '';
+      for (var name in extractKeys(namedArguments)) {
+        var type = JS('', '#[#]', namedArguments, name);
+        s = '$s$sep$name: ${runtimeTypeToString(type)}';
+        sep = ', ';
+      }
+      s = '$s}';
+    }
+    s = '${s}) -> ';
+    if (isVoid) {
+      s = '${s}void';
+    } else if (hasReturnType) {
+      s = '$s${runtimeTypeToString(returnType)}';
+    } else {
+      s = '${s}dynamic';
+    }
+    return s;
+  }
+}