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 Posted: Fri Nov 03, 2006 12:51 am Post subject: A non-dependent name becomes a dependent name? |
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template<typename T>
struct B
{
//void f();
};
template<typename T>
struct D:B<T>
{
using B<T>::f;
D()
{
f();
}
};
int main()
{}
According to the standard, f() in D: () is clearly a non-dependent
name, therefore looked up and bound at the time it's used.
But, since "using B<T>::f" introduced a name f into D, the name look up
will find it, thus bind the f() call to B<T>::f which is clearly a
dependent name.
Does this make f() a dependent name again? Or it's just a case where a
non-dependent name bounded to a dependent name?
--
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
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Alberto Ganesh Barbati
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| Posted: Fri Nov 03, 2006 5:22 am Post subject: Re: A non-dependent name becomes a dependent name? |
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pongba (AT) gmail (DOT) com ha scritto:
| Quote: | template<typename T
struct B
{
//void f();
};
template<typename T
struct D:B<T
{
using B<T>::f;
D()
{
f();
}
};
int main()
{}
According to the standard, f() in D:() is clearly a non-dependent
name, therefore looked up and bound at the time it's used.
But, since "using B<T>::f" introduced a name f into D, the name look up
will find it, thus bind the f() call to B<T>::f which is clearly a
dependent name.
Does this make f() a dependent name again? Or it's just a case where a
non-dependent name bounded to a dependent name?
|
§14.6.2/1 couldn't be clearer:
---
[...] In an expression of the form:
postfix-expression ( expression-list_opt )
where the postfix-expression is an identifier, the identifier denotes a
dependent name if and only if any of the expressions in the
expression-list is a type-dependent expression (14.6.2.2). [...]
---
As there's no expression-list in your case, f is never dependent. The
presence of the using declaration is irrelevant. Whether this is good or
bad, I can't tell. Certainly it's not the first not-so-intuitive name
lookup rule in the realm of templates. Fortunately, there's always the
"this->f()" notation if you want to be sure the name is dependent.
HTH,
Ganesh
--
[ See http://www.gotw.ca/resources/clcm.htm for info about ]
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