Add support for type checking of floating point arguments as [TypeChecking=Unrestricted]

Source/bindings/templates/methods.cpp

Index: Source/bindings/templates/methods.cpp
diff --git a/Source/bindings/templates/methods.cpp b/Source/bindings/templates/methods.cpp
index 3a63b52cd350694b59b8f23901b866de5b12a4b3..d33dd102285e36b9f2b12cb76c54681e47ca47db 100644
--- a/Source/bindings/templates/methods.cpp
+++ b/Source/bindings/templates/methods.cpp
@@ -94,12 +94,21 @@ if (UNLIKELY(info.Length() <= {{argument.index}})) {
 {% endif %}
 {% if argument.has_type_checking_interface %}
 {# Type checking for wrapper interface types (if interface not implemented,
-   throw TypeError), per http://www.w3.org/TR/WebIDL/#es-interface #}
+   throw a TypeError), per http://www.w3.org/TR/WebIDL/#es-interface #}
 if (info.Length() > {{argument.index}} && {% if argument.is_nullable %}!isUndefinedOrNull(info[{{argument.index}}]) && {% endif %}!V8{{argument.idl_type}}::hasInstance(info[{{argument.index}}], info.GetIsolate())) {
     {{throw_type_error(method, '"parameter %s is not of type \'%s\'."' %
                                (argument.index + 1, argument.idl_type)) | indent}}
     return;
 }
+{% elif argument.has_type_checking_unrestricted %}
+{# Type checking for non-finite floating point values (if NaN, +Infinity or
+   −Infinity, throw TypeError), per http://heycam.github.io/webidl/#es-float
+   and http://heycam.github.io/webidl/#es-double #}
+if (info.Length() > {{argument.index}} && {% if argument.is_nullable %}!isUndefinedOrNull(info[{{argument.index}}]) && {% endif %}!std::isfinite(info[{{argument.index}}]->NumberValue())) {

[Nils Barth (inactive), 2014/04/28 10:40:45]

Actually it's not that bad;
can just use std::isfinite:
!std::isfinite(info[{{argument.index}}]->NumberValue())
...but it would still be nicer to do via V8 as:
info[{{argument.index}}]->IsSpecial()
...as we just need to do a simple check, not compute the value.

[fs, 2014/04/28 10:58:34]

But in a case like:

{ valueOf: function() { return NaN; } }

it really won't be a "simple" check. But maybe that's uncommon enough to not
matter much... (Or to put it another way: What would IsSpecial() mean on a
generic v8::Value?)

That being said though - why not do the finiteness check after
v8_value_to_local_cpp_value (i.e, on the cppValue)?

[Nils Barth (inactive), 2014/04/30 01:58:02]

Good point; presumably would need to be IsSpecialDouble or something, but
wouldn't make sense for non-numbers.
That's even better!
Done; now it's just a simple std::isfinite check, which is as efficient as we
can get.
This presumably just checks the biased exponent field, which is how non-numbers
are stored:
http://en.wikipedia.org/wiki/IEEE_754-1985#Representation_of_non-numbers
...and is the same check that V8 does:
https://code.google.com/p/chromium/codesearch#chromium/src/v8/src/double.h&q=...

Currently type checking is in two places: before and after storing the cppValue,
and it's generally simpler to put it after, as you suggest.

+    {{throw_type_error(method, '"%s parameter %s is non-finite."' %
+                               (argument.idl_type, argument.index + 1)) | indent}}
+    return;
+}
 {% endif %}
 {% if argument.is_callback_interface %}
 {# FIXME: remove EventListener special case #}