Merge 2024-03 CWG Motion 9

P2573R2 = delete("should have a reason");

Author: tkoeppe

source/declarations.tex

@@ -6331,7 +6331,13 @@
     \opt{ctor-initializer} compound-statement\br
     function-try-block\br
     \terminal{=} \keyword{default} \terminal{;}\br
-    \terminal{=} \keyword{delete} \terminal{;}
+    deleted-function-body
+\end{bnf}
+
+\begin{bnf}
+\nontermdef{deleted-function-body}\br
+    \terminal{=} \keyword{delete} \terminal{;}\br
+    \terminal{=} \keyword{delete} \terminal{(} unevaluated-string \terminal{)} \terminal{;}
 \end{bnf}
 
 Any informal reference to the body of a function should be interpreted as a reference to
@@ -6589,11 +6595,8 @@
 \indextext{definition!function!deleted}%
 
 \pnum
-A \defnadj{deleted}{definition} of a function is
-a function definition whose
-\grammarterm{function-body}
-is of the form
-\tcode{= delete ;}
+A \defnadj{deleted}{definition} of a function is a function definition
+whose \grammarterm{function-body} is a \grammarterm{deleted-function-body}
 or an explicitly-defaulted definition of the function where the function is
 defined as deleted.
 A \defnadj{deleted}{function} is
@@ -6603,6 +6606,12 @@
 \pnum
 A program that refers to a deleted function implicitly or explicitly, other
 than to declare it, is ill-formed.
+
+\recommended
+The resulting diagnostic message should include
+the text of the \grammarterm{unevaluated-string},
+if one is supplied.
+
 \begin{note}
 This includes calling the function
 implicitly or explicitly and forming a pointer or pointer-to-member to the
@@ -6611,6 +6620,9 @@
 function selected by overload resolution is referenced. The implicit
 odr-use\iref{term.odr.use} of a virtual function does not, by itself,
 constitute a reference.
+The \grammarterm{unevaluated-string}, if present,
+can be used to explain the rationale for deletion and/or
+to suggest an alternative.
 \end{note}
 
 \pnum

source/preprocessor.tex

@@ -1857,6 +1857,7 @@
 \defnxname{cpp_decltype_auto}                     & \tcode{201304L} \\ \rowsep
 \defnxname{cpp_deduction_guides}                  & \tcode{201907L} \\ \rowsep
 \defnxname{cpp_delegating_constructors}           & \tcode{200604L} \\ \rowsep
+\defnxname{cpp_deleted_function}                  & \tcode{202403L} \\ \rowsep
 \defnxname{cpp_designated_initializers}           & \tcode{201707L} \\ \rowsep
 \defnxname{cpp_enumerator_attributes}             & \tcode{201411L} \\ \rowsep
 \defnxname{cpp_explicit_this_parameter}           & \tcode{202110L} \\ \rowsep