I have a code:
void f(int&& i) {
auto lambda = [](int&& j) { (void)j; }
lambda(i);
}
int main() {
f(5);
}
Clang++ gives an error: no known conversion from 'int' to 'int &&' for 1st argument
Why the i
changes its type to int
when being passed to the lambda()
?
There are two elements at work here:
i
has type int&&
, or "rvalue reference to int
", where "rvalue reference" is the name for the &&
feature, allowing binding rvalues to a reference; i
has a name and so the expression naming it is an lvalue, regardless of its type or what the standard committee decided to call that type. :)(Note that the expression that looks like i
has type int
, not int&&
, because reasons. The rvalue ref is lost when you start to use the parameter, unless you use something like std::move
to get it back.)