rspec/rules/S6031/cfamily/rule.adoc

== Why is this an issue?

``++std::forward++`` forwards lvalues either as lvalues or as rvalues based on its template argument.

``++std::forward++`` should always take as a non-template argument a forwarding reference which is defined by the standard as:

_rvalue reference to a cv-unqualified template parameter that does not represent a template parameter of a class template._


If you don’t pass forwarding reference as an argument to ``++std::forward++`` S5417 will be triggered.

If you don’t pass the template parameter referred to by the forwarded reference or the ``++decltype++`` of the forwarded expression this rule will be triggered.


=== Noncompliant code example

[source,cpp]
----
template <class T>
void g(T&& t);

template <class T>
void f(T&& t) {
 g(std::forward<T&&>(t)); // Noncompliant
 g(std::forward<T&>(t)); // Noncompliant
}
----


=== Compliant solution

[source,cpp]
----
template <class T>
void g(T&& t);

template <class T>
void f(T&& t) {
  g(std::forward<T>(t)); // Compliant
}

struct StrWrapper {
  std::string s = "rand";
  std::string getStr() && {
    return s;
  }
  std::string& getStr() & {
    return s;
  }
};
template <class T>
void fstr(T&& str);

template <class T>
void wrapper(T&& strWrapper ) {
  fstr(forward<decltype(forward<T>(strWrapper).getStr())>(forward<T>(strWrapper).getStr())); // Compliant
}
----