Don't try to declare a local variable with no name

Reason

There is no such thing. What looks to a human like a variable without a name is to the compiler a statement consisting of a temporary that immediately goes out of scope.

Example, bad

void f()
{
    lock_guard<mutex>{mx};   // Bad
    // ...
}

This declares an unnamed lock_guard object that immediately goes out of scope at the point of the semicolon. This is not an uncommon mistake. In particular, this particular example can lead to hard-to-find race conditions.

Note

Unnamed function arguments are fine.

Enforcement

Flag statements that are just a temporary.