Browsing Spanish translation

If 'rtype' is NULL_TREE at this point it means that
we have seen no @interface corresponding to that
class name, only a @class declaration (alternatively,
this was a call such as [objc_getClass("SomeClass")
alloc], where we've never seen the @interface of
SomeClass).  So, we have a class name (class_tree)
but no actual details of the class methods.  We won't
be able to check that the class responds to the
method, and we will have to guess the method
prototype.  Emit a warning, then keep going (this
will use any method with a matching name, as if the
receiver was of type 'Class').
We could not find an @interface declaration, and
there are no protocols attached to the receiver,
so we can't complete the check that the receiver
responds to the method, and we can't retrieve the
method prototype.  But, because the receiver has
a well-specified class, the programmer did want
this check to be performed.  Emit a warning, then
keep going as if it was an 'id'.  To remove the
warning, either include an @interface for the
class, or cast the receiver to 'id'.  Note that
rtype is an IDENTIFIER_NODE at this point.

Do not do any encoding, produce an error and keep going.