C ++模板类型规范

Question

I have an empty class with the same name as a blank function. When I try to pass this class as a template parameter I receive an error:

" type/value mismatch at argument 1 "

" 'Test' is not a valid template type argument for parameter '_Ty' "

Consider:

#include <vector>

void Test() {
}

class Test {
};

int main() {
    std::vector<Test> test;
}

Changing to

std::vector<class Test>

seems to work, but I was not able to found out, whether this is required by a standard, or just randomly supported by my compiler.

Can someone point out, how to solve this issue or link to standard, that requires this behavior?

Answer 1

Yes you have to use the keyword class prepended to the name for disambiguation, which resulting in an elaborated type specifier.

[class.name]/2 :

(emphasis mine)

If a class name is declared in a scope where a variable, function, or enumerator of the same name is also declared, then when both declarations are in scope, the class can be referred to only using an elaborated-type-specifier ([basic.lookup.elab]). [ Example:

 struct stat { // ... }; stat gstat; // use plain stat to define variable int stat(struct stat*); // redeclare stat as function void f() { struct stat* ps; // struct prefix needed to name struct stat stat(ps); // call stat() } 

— end example ]

And [dcl.type.elab] :

elaborated-type-specifier:

• class-key attribute-specifier-seq _opt nested-name-specifier _opt identifier
• class-key simple-template-id
• class-key nested-name-specifier template _opt simple-template-id
• enum nested-name-specifier _opt identifier