When a type is introduced via a using declaration, it is not fully recognized by the code model: the name is rendered colorless, have no tooltip, but it participates in code completion.

#include <string>
using std::string;

int main()
{
    string s; // "string" is colorless and has no tooltip
    s. // code completion works here
}

Introducing types via type aliases (using string = std::string) works.

Version 5.10.230370 (23.03.70)