The safe_alias level of T, defaulting unannotated types to maybe_value.
Declared in <folly/lang/SafeAlias-fwd.h>
template<typename T>
inline constexpr safe_alias lenient_safe_alias_of_v = safe_alias_of<T, safe_alias::maybe_value>::value;
For low-risk APIs, where "vanilla C++ usability" outweighs safety.