https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109947
--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> --- (In reply to Martin Seemann from comment #3) > So it comes down to how to interpret the "Effects:" clause: Does "Equivalent > to <statements involving std::move(value())>" mean that all restrictions of > `value()` apply transitively or is it merely an implementation hint? The former. The standard says: Whenever the Effects element specifies that the semantics of some function F are Equivalent to some code sequence, then the various elements are interpreted as follows. If F’s semantics specifies any Constraints or Mandates elements, then those requirements are logically imposed prior to the equivalent-to semantics. Next, the semantics of the code sequence are determined by the Constraints, Mandates, Preconditions, Effects, Synchronization, Postconditions, Returns, Throws, Complexity, Remarks, and Error conditions specified for the function invocations contained in the code sequence. The value returned from F is specified by F’s Returns element, or if F has no Returns element, a non-void return from F is specified by the return statements (8.7.4) in the code sequence. If F’s semantics contains a Throws, Postconditions, or Complexity element, then that supersedes any occurrences of that element in the code sequence. > (Strangely enough, in the "Effects:" clause of `value_or()&&` the expression > `std::move(**this)` is used instead of `std::move(value())`. Maybe this is > an oversight/inconsistency of the standard.) Yes. The spec were written by different people at different times.
