Implement function proxies (except for their use as constructors).

src/runtime.js

Index: src/runtime.js
diff --git a/src/runtime.js b/src/runtime.js
index 4b600df7360b3431f9a3834937a022e35d1a4648..82ff2624cb583a3b4a5ee7f4f463b0a878f33e44 100644
--- a/src/runtime.js
+++ b/src/runtime.js
@@ -365,7 +365,7 @@ function IN(x) {
 // an expensive ToBoolean conversion in the generated code.
 function INSTANCE_OF(F) {
   var V = this;
-  if (!IS_FUNCTION(F)) {
+  if (!IS_SPEC_FUNCTION(F)) {
     throw %MakeTypeError('instanceof_function_expected', [V]);
   }
 
@@ -405,7 +405,11 @@ function FILTER_KEY(key) {
 function CALL_NON_FUNCTION() {
   var delegate = %GetFunctionDelegate(this);
   if (!IS_FUNCTION(delegate)) {
-    throw %MakeTypeError('called_non_callable', [typeof this]);
+    if (%IsJSFunctionProxy(this)) {

[Kevin Millikin (Chromium), 2011/09/08 17:30:40]

Can we get into this case, where CALL_NON_FUNCTION is invoked on a function
proxy?  If so, another design is to have %GetFunctionDelegate return the call
trap.  I don't know if that makes things simpler, or less simple, or about the
same.

[rossberg, 2011/09/09 17:05:30]

Done (subsuming part of change 7849021).

+      delegate = %GetCallTrap(this);
+    } else {
+      throw %MakeTypeError('called_non_callable', [typeof this]);
+    }
   }
   return delegate.apply(this, arguments);
 }
@@ -414,12 +418,44 @@ function CALL_NON_FUNCTION() {
 function CALL_NON_FUNCTION_AS_CONSTRUCTOR() {
   var delegate = %GetConstructorDelegate(this);
   if (!IS_FUNCTION(delegate)) {
-    throw %MakeTypeError('called_non_callable', [typeof this]);
+    if (%IsJSFunctionProxy(this)) {
+      delegate = %GetConstructTrap(this);
+    } else {
+      throw %MakeTypeError('called_non_callable', [typeof this]);
+    }
   }
   return delegate.apply(this, arguments);
 }
 
 
+function CALL_FUNCTION_PROXY() {
+  var arity = %_ArgumentsLength() - 1;
+  var proxy = arguments[arity];  // The proxy comes in as an additional arg.

[Kevin Millikin (Chromium), 2011/09/08 17:30:40]

You can also use %_Arguments(arity) to get the arguments without allocating the
arguments object.

[rossberg, 2011/09/09 17:05:30]

Done (although we have to materialize the arguments object anyway).

+  var trap = %GetCallTrap(proxy);
+  // TODO(rossberg): hm, shouldn't I be using $Function and friends?
+  // But how do I get it in a builtin?
+  return global.Function.prototype.apply.call(

[Kevin Millikin (Chromium), 2011/09/08 17:30:40]

You can't, the JS builtins are called with the context of their caller (and
don't depend on it).  I think you'll have to implement a runtime function to do
some of the work here.

[rossberg, 2011/09/09 17:05:30]

I implemented an %Apply native.

+    trap, this, global.Array.prototype.slice.call(arguments, 0, arity));
+}
+
+
+function CALL_FUNCTION_PROXY_AS_CONSTRUCTOR(proxy) {
+  var trap = %GetConstructTrap(proxy);
+  var receiver = void 0;
+  if (!IS_UNDEFINED(trap)) {
+    trap = %GetCallTrap(proxy);
+    var proto = proxy.prototype;
+    if (!IS_SPEC_OBJECT(proto) && proto !== null) {
+      throw MakeTypeError("proto_object_or_null", [proto]);
+    }
+    receiver = new global.Object();
+    receiver.__proto__ = proto;
+  }
+  return global.Function.prototype.apply.call(
+    trap, this, global.Array.prototype.shift.call(arguments));
+}
+
+
 function APPLY_PREPARE(args) {
   var length;
   // First check whether length is a positive Smi and args is an
@@ -427,7 +463,8 @@ function APPLY_PREPARE(args) {
   // that takes care of more eventualities.
   if (IS_ARRAY(args)) {
     length = args.length;
-    if (%_IsSmi(length) && length >= 0 && length < 0x800000 && IS_FUNCTION(this)) {
+    if (%_IsSmi(length) && length >= 0 && length < 0x800000 &&
+        IS_SPEC_FUNCTION(this)) {
       return length;
     }
   }
@@ -441,7 +478,7 @@ function APPLY_PREPARE(args) {
     throw %MakeRangeError('stack_overflow', []);
   }
 
-  if (!IS_FUNCTION(this)) {
+  if (!IS_SPEC_FUNCTION(this)) {
     throw %MakeTypeError('apply_non_function', [ %ToString(this), typeof this ]);
   }
 
@@ -609,13 +646,13 @@ function IsPrimitive(x) {
 // ECMA-262, section 8.6.2.6, page 28.
 function DefaultNumber(x) {
   var valueOf = x.valueOf;
-  if (IS_FUNCTION(valueOf)) {
+  if (IS_SPEC_FUNCTION(valueOf)) {
     var v = %_CallFunction(x, valueOf);
     if (%IsPrimitive(v)) return v;
   }
 
   var toString = x.toString;
-  if (IS_FUNCTION(toString)) {
+  if (IS_SPEC_FUNCTION(toString)) {
     var s = %_CallFunction(x, toString);
     if (%IsPrimitive(s)) return s;
   }
@@ -627,13 +664,13 @@ function DefaultNumber(x) {
 // ECMA-262, section 8.6.2.6, page 28.
 function DefaultString(x) {
   var toString = x.toString;
-  if (IS_FUNCTION(toString)) {
+  if (IS_SPEC_FUNCTION(toString)) {
     var s = %_CallFunction(x, toString);
     if (%IsPrimitive(s)) return s;
   }
 
   var valueOf = x.valueOf;
-  if (IS_FUNCTION(valueOf)) {
+  if (IS_SPEC_FUNCTION(valueOf)) {
     var v = %_CallFunction(x, valueOf);
     if (%IsPrimitive(v)) return v;
   }