Functions returning lvalues, always return lvalue references

Question

Scott meyers in item 3 of effective c++ says

Applying decltype to a name yields the declared type for that name. Names are typically lvalue expressions, but that doesn’t affect decltype’s behavior. For lvalue expressions more complicated than names, however, decltype generally ensures that the type reported is an lvalue reference. That is, if an lvalue expression other than a name has type T, decltype reports that type as T&. This seldom has any impact, because the type of most lvalue expressions inherently includes an lvalue reference qualifier. Functions returning lvalues, for example, always return lvalue references.

What does it mean when he says Functions returning lvalues, for example, always return lvalue references

Answer 1

It means what it says!

There is no way to make a function, such that its return type is not T&, yet calling it results in an lvalue expression.

Every other return type results in the function call being an rvalue expression.

This is intuitive when you consider that the only way to "return" something that already exists, is by reference — the result of a function call is otherwise always a "temporary", whether because it's copying some local variable, or because it's moving from some local variable.

The would-be exception to this rule, returning T&&, doesn't apply either because these produce rvalue expressions (which is what makes move semantics work, since only rvalue expressions can go on to bind to T&& parameters).

Scott is reporting a consequence of the rules of the language, and telling us that the same consequence was used as a justification for one of the rules of decltype.

Arguably, he could have more clearly phrased it thus:

The only functions whose calls evaluate to lvalues, are those that return lvalue references.