[ 2020-01 Priority set to 3 after review on the reflector. ]

Previous resolution [SUPERSEDED]:

This wording is relative to N4842.

1. Modify [range.range] as indicated:

   template<class T>
     concept safe_range =
       range<T> &&
         (is_lvalue_reference_v<T> || enable_safe_range<remove_cvref_t<T>>);
   

   -5- Given an expression E such that decltype((E)) is T,A type T models safe_range only if:

   1. (5.1) — is_lvalue_reference_v<T> is true, or

   2. (5.2) — given an expression E such that decltype((E)) is T, if the validity of iterators obtained from the object denoted by E is not tied to the lifetime of that object.

   -6- [Note: Since the validity of iterators is not tied to the lifetime of an object whose type models safe_range, aA function can accept arguments of such a type that models safe_range by value and return iterators obtained from it without danger of dangling. — end note]