Merge 2023-06 LWG Motion 8

P2538R1 ADL-proof std::projected

Author: tkoeppe

source/iterators.tex

@@ -2512,16 +2512,18 @@
 \indexlibraryglobal{projected}%
 \begin{codeblock}
 namespace std {
-  template<@\libconcept{indirectly_readable}@ I, @\libconcept{indirectly_regular_unary_invocable}@<I> Proj>
-  struct projected {
-    using value_type = remove_cvref_t<indirect_result_t<Proj&, I>>;
-    indirect_result_t<Proj&, I> operator*() const;              // \notdef
+  template<class I, class Proj>
+  struct @\exposidnc{projected-impl}@ {                               // \expos
+    struct @\exposidnc{type}@ {                                       // \expos
+      using value_type = remove_cvref_t<indirect_result_t<Proj&, I>>;
+      using difference_type = iter_difference_t<I>;     // present only if \tcode{I}
+                                                        // models \libconcept{weakly_incrementable}
+      indirect_result_t<Proj&, I> operator*() const;    // \notdef
+    };
   };
 
-  template<@\libconcept{weakly_incrementable}@ I, class Proj>
-  struct incrementable_traits<projected<I, Proj>> {
-    using difference_type = iter_difference_t<I>;
-  };
+  template<@\libconcept{indirectly_readable}@ I, @\libconcept{indirectly_regular_unary_invocable}@<I> Proj>
+    using projected = @\exposid{projected-impl}@<I, Proj>::@\exposid{type}@;
 }
 \end{codeblock}