Why do I get an error trying to call a template member function with an explicit type parameter?
I don't get it, it seems to me that the call to f
is completely unambiguous, but it fails to compile with expected primary-expression before ‘int’
. If I comment out the line with the call to f
, it compiles fine.
template<typename T>
struct A {
template<typename S>
void f() { }
};
template<typename T>
struct B : A<T> {
void g() {
开发者_开发知识库 this->f<int>();
}
};
This is due to a really obscure provision of the standard in which if you have a template that tries to access a template function in an object whose type depends on a template argument, you have to use the template
keyword in a weird way:
this->template f<int>();
This is similar to the weirdness with typename
that comes up with dependent types, except as applied to functions. In particular, if you leave out the template
keyword, there's a parsing ambiguity between
this->f<int>()
(what you intended), and
((this->f) < int) > ()
which makes no sense (hence your error). The use of the keyword template
here disambiguates and forces the compiler to recognize that it's looking at a perfectly valid call to a templated member function rather than a garbled mass of symbols.
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