P0475R1 LWG2511 Guaranteed copy elision for piecewise construction

Author: jensmaurer

source/utilities.tex

@@ -12762,17 +12762,13 @@
 \end{itemdecl}
 
 \begin{itemdescr}
-\pnum
-\requires All of the types in \tcode{Args1} and \tcode{Args2} shall be
-\tcode{CopyConstructible} (\tref{copyconstructible}).
-
 \pnum
 \effects Constructs a \tcode{tuple} object \tcode{xprime} from \tcode{x} by the
 following rules:
 \begin{itemize}
 \item If \tcode{uses_allocator_v<T1, inner_allocator_type>} is \tcode{false} and
 \tcode{is_constructible_v<T1,\\ Args1...>} is \tcode{true},
-then \tcode{xprime} is \tcode{x}.
+then \tcode{xprime} is \tcode{tuple<Args1\&\&...>(std::move(x))}.
 
 \item Otherwise, if \tcode{uses_allocator_v<T1, inner_allocator_type>} is \tcode{true}
 and
@@ -12782,23 +12778,24 @@
 \begin{codeblock}
 tuple_cat(
     tuple<allocator_arg_t, inner_allocator_type&>(allocator_arg, inner_allocator()),
-    std::move(x))
+    tuple<Args1&&...>(std::move(x)))
 \end{codeblock}
 
 \item Otherwise, if \tcode{uses_allocator_v<T1, inner_allocator_type>} is
 \tcode{true} and
 \tcode{is_construct\-ible_v<T1, Args1..., inner_allocator_type\&>} is \tcode{true},
 then \tcode{xprime} is:
 \begin{codeblock}
-tuple_cat(std::move(x), tuple<inner_allocator_type&>(inner_allocator()))
+tuple_cat(tuple<Args1&&...>(std::move(x)),
+          tuple<inner_allocator_type&>(inner_allocator()))
 \end{codeblock}
 
 \item Otherwise, the program is ill-formed.
 \end{itemize}
 and constructs a \tcode{tuple} object \tcode{yprime} from \tcode{y} by the following rules:
 \begin{itemize}
 \item If \tcode{uses_allocator_v<T2, inner_allocator_type>} is \tcode{false} and
-\tcode{is_constructible_v<T2,\\ Args2...>} is \tcode{true}, then \tcode{yprime} is \tcode{y}.
+\tcode{is_constructible_v<T2,\\ Args2...>} is \tcode{true}, then \tcode{yprime} is \tcode{tuple<Args2\&\&...>(std::move(y)}.
 
 \item Otherwise, if \tcode{uses_allocator_v<T2, inner_allocator_type>} is \tcode{true}
 and
@@ -12808,15 +12805,16 @@
 \begin{codeblock}
 tuple_cat(
     tuple<allocator_arg_t, inner_allocator_type&>(allocator_arg, inner_allocator()),
-    std::move(y))
+    tuple<Args2&&...>(std::move(y)))
 \end{codeblock}
 
 \item Otherwise, if \tcode{uses_allocator_v<T2, inner_allocator_type>} is
 \tcode{true} and
 \tcode{is_constructible_v<T2, Args2..., inner_allocator_type\&>} is \tcode{true},
 then \tcode{yprime} is:
 \begin{codeblock}
-tuple_cat(std::move(y), tuple<inner_allocator_type&>(inner_allocator()))
+tuple_cat(tuple<Args2&&...>(std::move(y)),
+          tuple<inner_allocator_type&>(inner_allocator()))
 \end{codeblock}
 
 \item Otherwise, the program is ill-formed.