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* Adopt the Library Fundamentals TS make_array design for the sequence factories make_array, make_deque, make_vector, make_list, make_forward_list and make_indirect_vector now follow the Library Fundamentals TS std::experimental::make_array design: a defaulted leading template parameter selects the element type explicitly, falling back to the decayed common type of the arguments when it is not supplied. A shared trait (etl::private_make::element_type) performs the selection lazily, so common_type is not instantiated when the element type is explicit. This fixes the explicit-element-type calling style for the four common-type factories, where make_vector<char>(lvalue) never compiled: the explicit argument pinned the first pack parameter to char, making it a char&& that no lvalue can bind to. It also gives make_array and make_deque the deduced form (e.g. make_array(1, 2L) is array<long, 2>) for free. All arguments are converted with static_cast, as in the make_array const-lvalue fix, so const-qualified lvalues and narrowing initialisers work in both forms. Intentional behaviour change: an explicit element type now converts every argument instead of pinning only the first. make_vector<char>(0, 1, ...) previously produced vector<int> - the explicit char affected only the first argument and the element type was still the common type - and now produces vector<char>. test_make_vector documented the old behaviour and has been updated. The keyed set and map factories are unchanged: their key/mapped types are separate mandatory template parameters ahead of a fully-deduced pack, so the explicit-type style already works, and retrofitting deduction there would interact with the defaulted comparator/hash parameters. Adds explicit-element-type tests for the four common-type factories (const/non-const lvalues plus narrowing initialisers) and deduced-element-type tests for make_array and make_deque, and updates the four documented signatures. * Address review comments on the make_xxx factory design - Forward same-type arguments in the make_xxx factories instead of casting them. static_cast produced a prvalue that, before C++17, had to be materialised through the move constructor, rejecting copyable-but-non-movable element types. The new private_make::convert helper forwards arguments that already have the element type and static_casts the rest. - Drop ETL_NOEXCEPT from make_array: conversions can throw, and the other factories do not declare it. - Remove the redundant etl::decay in element_type<void, ...>; etl::common_type already decays its arguments. - Stop leaking the etl::private_make implementation namespace into the documented factory signatures. * Add a test for make_array with an explicit element type and no arguments etl::make_array<int>() produces an empty etl::array<int, 0> and now has a regression test. A call with neither an element type nor arguments remains ill-formed, matching the Library Fundamentals TS: there is nothing to deduce the element type from. The array documentation now states this explicitly. --------- Co-authored-by: John Wellbelove <jwellbelove@users.noreply.github.com> Co-authored-by: Roland Reichwein <Roland.Reichwein@bmw.de> |
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