745361 - Handle conversion rules totally break static typing

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Luke Wagner [:luke]]

This type checks but I don't think it should

  RootedVarString r(...);
  HandleObject h = r;

I think the solution is to remove this constructor and fix other things with explicit (restrict) casts.

  template <class T>
  template <class U>
  Handle<T>::Handle(const RootedVar<U> &);

and the analogous one for Root<U>.

Also, can we move Handle out of jsprvtd.h?

Comment 1

[Brian Hackett [Laid off!]]

Attachment: patch

Oops, this constructor was missing a testAssign, which is supposed to only allow handle assignments that follow normal C++ assignment rules for the wrapped type.  See the other Handle constructors, which are also templated on a type other than the handle.  Requiring casts whenever converting between handles of different but compatible types would be a mess I think, with all the subclassing we do for objects and strings.

Comment 2

[Luke Wagner [:luke]]

Comment on attachment 615047 [details] [diff] [review]
patch

Ahh, I didn't see testAssign.  Cool.

Comment 3

[Brian Hackett [Laid off!]]

https://hg.mozilla.org/integration/mozilla-inbound/rev/4597dcf0842a

Comment 4

[(no longer active)]

https://hg.mozilla.org/mozilla-central/rev/4597dcf0842a