borrowed_iterator_t (custom), renamed source_last

to `in` just like C++20 ranges copy functions.
Also renamed view/detail/core.h to misc.h and tweaked static_assert message

auxi/type_traits.h

@@ -10,6 +10,17 @@
 
 #include <iterator>
 
+//! Users can define (to override __cpp_lib_ranges or to not pay for include)
+#ifndef OEL_STD_RANGES
+	#if __cpp_lib_ranges < 201911
+	#define OEL_STD_RANGES  0
+	#else
+	#define OEL_STD_RANGES  1
+	#endif
+#endif
+#if OEL_STD_RANGES
+#include <ranges>
+#endif
 
 #if !__has_include(<boost/config.hpp>)
 	#define OEL_NO_BOOST  1
@@ -90,6 +101,19 @@ using iterator_t = decltype( begin(std::declval<Range &>()) );
 template< typename Range >
 using sentinel_t = decltype( end(std::declval<Range &>()) );
 
+//! Like std::ranges::borrowed_iterator_t, but doesn't require that Range has end()
+template< typename Range >
+using borrowed_iterator_t =
+#if OEL_STD_RANGES
+	std::conditional_t<
+		std::is_lvalue_reference_v<Range> or std::ranges::enable_borrowed_range< std::remove_cvref_t<Range> >,
+		iterator_t<Range>,
+		std::ranges::dangling
+	>;
+#else
+	iterator_t<Range>;
+#endif
+
 #if __cpp_lib_concepts < 201907
 	template< typename Iterator >
 	using iter_difference_t = typename std::iterator_traits<Iterator>::difference_type;

dynarray.h

@@ -33,10 +33,10 @@ void erase_unstable(dynarray<T, A> & d, size_t index)  { d.erase_unstable(d.begi
 //!@{
 // Overloads of generic functions for inserting into container (in range_algo.h)
 template< typename T, typename A, typename InputRange >  inline
-void assign(dynarray<T, A> & dest, InputRange && source)  { dest.assign(source); }
+void assign(dynarray<T, A> & dest, InputRange && source)  { dest.assign(static_cast<InputRange &&>(source)); }
 
 template< typename T, typename A, typename InputRange >  inline
-void append(dynarray<T, A> & dest, InputRange && source)  { dest.append(source); }
+void append(dynarray<T, A> & dest, InputRange && source)  { dest.append(static_cast<InputRange &&>(source)); }
 
 template< typename T, typename A >  inline
 void append(dynarray<T, A> & dest, size_t n, const T & val)  { dest.append(n, val); }
@@ -153,7 +153,7 @@ class dynarray
 	* Any elements held before the call are either assigned to or destroyed. */
 	template< typename InputRange >
 	auto assign(InputRange && source)
-	->	iterator_t<InputRange>           { return _doAssign(oel::adl_begin(source), _detail::CountOrEnd(source)); }
+	->	borrowed_iterator_t<InputRange>   { return _doAssign(oel::adl_begin(source), _detail::CountOrEnd(source)); }
 
 	void assign(size_type count, const T & val)   { clear();  append(count, val); }
 
@@ -167,7 +167,7 @@ class dynarray
 	* where `end(source)` is not needed if `source.size()` exists. */
 	template< typename InputRange >
 	auto append(InputRange && source)
-	->	iterator_t<InputRange>             { return _append(oel::adl_begin(source), _detail::CountOrEnd(source)); }
+	->	borrowed_iterator_t<InputRange>    { return _append(oel::adl_begin(source), _detail::CountOrEnd(source)); }
 	//! Equivalent to `std::vector::insert(end(), il)`
 	void append(std::initializer_list<T> il)   { append<>(il); }
 	/**

range_algo.h

@@ -49,7 +49,7 @@ constexpr void erase_adjacent_dup(Container & c)   { _detail::Unique(c, int{});
 template< typename Iterator >
 struct copy_return
 {
-	Iterator source_last;
+	Iterator in;
 };
 /**
 * @brief Copies the elements in source into the range beginning at dest
@@ -61,8 +61,10 @@ struct copy_return
 * (Views can be used for all functions taking a range as source)  */
 template< typename SizedInputRange, typename RandomAccessIter >  inline
 auto copy_unsafe(SizedInputRange && source, RandomAccessIter dest)
-->	copy_return<decltype(begin(source))>
-	                                    { return {_detail::CopyUnsf(begin(source), _detail::Size(source), dest)}; }
+->	copy_return< borrowed_iterator_t<SizedInputRange> >
+	{
+		return{ _detail::CopyUnsf(begin(source), _detail::Size(source), dest) };
+	}
 /**
 * @brief Copies the elements in source range into dest range, throws std::out_of_range if dest is smaller than source
 * @return `begin(source)` incremented by the number of elements in source
@@ -71,7 +73,7 @@ auto copy_unsafe(SizedInputRange && source, RandomAccessIter dest)
 * Requires that `source.size()` or `end(source) - begin(source)` is valid, and that dest models random_access_range. */
 template< typename SizedInputRange, typename RandomAccessRange >
 auto copy(SizedInputRange && source, RandomAccessRange && dest)
-->	copy_return<decltype(begin(source))>;
+->	copy_return< borrowed_iterator_t<SizedInputRange> >;
 /**
 * @brief Copies as many elements from source as will fit in dest
 * @return true if all elements were copied, false means truncation happened
@@ -110,12 +112,12 @@ constexpr auto insert_range(Container & dest, ContainerIterator pos, InputRange
 
 ////////////////////////////////////////////////////////////////////////////////
 //
-// Only implementation
+// Just implementation
 
 
 template< typename SizedInputRange, typename RandomAccessRange >
 auto oel::copy(SizedInputRange && src, RandomAccessRange && dest)
-->	copy_return<decltype(begin(src))>
+->	copy_return< borrowed_iterator_t<SizedInputRange> >
 {
 	if (as_unsigned(_detail::Size(src)) <= as_unsigned(_detail::Size(dest)))
 		return oel::copy_unsafe(src, begin(dest));

unit_test/dynarray_mutate_gtest.cpp

@@ -928,3 +928,14 @@ TEST_F(dynarrayTest, misc)
 		test.push_back(1);
 	}
 }
+
+#if OEL_STD_RANGES
+void testDanglingReturn()
+{
+	dynarray<int> d;
+	auto i0 = d.assign(dynarray<int>{});
+	auto i1 = d.append(dynarray<int>{});
+	static_assert(std::is_same_v<decltype(i0), std::ranges::dangling>);
+	static_assert(std::is_same_v<decltype(i1), std::ranges::dangling>);
+}
+#endif

unit_test/range_algo_gtest.cpp

@@ -88,13 +88,13 @@ TEST(rangeTest, copy)
 	EXPECT_FALSE(success);
 
 	ASSERT_EQ(4, test[N]);
-	auto l = oel::copy(test2, test).source_last;
+	auto l = oel::copy(test2, test).in;
 	EXPECT_EQ(-7, test[N]);
 	EXPECT_TRUE(std::end(test2) == l);
 	{
 		std::list<std::string> li{"aa", "bb"};
 		std::array<std::string, 2> strDest;
-		auto sLast = oel::copy(view::move(li), strDest).source_last;
+		auto sLast = oel::copy(view::move(li), strDest).in;
 		EXPECT_EQ("aa", strDest[0]);
 		EXPECT_EQ("bb", strDest[1]);
 		EXPECT_TRUE(li.begin()->empty());

view/counted.h

@@ -7,7 +7,7 @@
 
 
 #include "../util.h"
-#include "detail/core.h"
+#include "detail/misc.h"
 
 /** @file
 */

view/detail/core.h → view/detail/misc.h

@@ -8,18 +8,6 @@
 
 #include "../../auxi/type_traits.h"
 
-//! Users may define (to override __cpp_lib_ranges or to not pay for include)
-#ifndef OEL_STD_RANGES
-	#if __cpp_lib_ranges < 201911
-	#define OEL_STD_RANGES  0
-	#else
-	#define OEL_STD_RANGES  1
-	#endif
-#endif
-#if OEL_STD_RANGES
-#include <ranges>
-#endif
-
 namespace oel
 {
 

view/move.h

@@ -7,7 +7,6 @@
 
 
 #include "all.h"
-#include "detail/core.h"
 
 /** @file
 */

view/subrange.h

@@ -7,7 +7,7 @@
 
 
 #include "../util.h"  // for as_unsigned
-#include "detail/core.h"
+#include "detail/misc.h"
 
 /** @file
 */

view/transform_iterator.h

@@ -7,7 +7,7 @@
 
 
 #include "../util.h"  // for TightPair
-#include "detail/core.h"
+#include "detail/misc.h"
 
 /** @file
 */