From 28c4ef0522ff70d04856e9963881b8973294bc2a Mon Sep 17 00:00:00 2001
From: Jens Maurer <Jens.Maurer@gmx.net>
Date: Mon, 19 Jun 2023 23:53:33 +0200
Subject: [PATCH 1/2] P2169R4 A nice placeholder with no name

---
 source/basic.tex        | 39 ++++++++++++++++++++++++++++++++++++---
 source/declarations.tex | 16 ++++++++++++++--
 source/preprocessor.tex |  1 +
 3 files changed, 51 insertions(+), 5 deletions(-)

diff --git a/source/basic.tex b/source/basic.tex
index 20d8970469..a87a7bdb73 100644
--- a/source/basic.tex
+++ b/source/basic.tex
@@ -987,14 +987,32 @@
 \end{codeblock}
 \end{example}
 
+\pnum
+A declaration is \defnx{name-independent}{declaration!name-independent}
+if its name is \tcode{_} and it declares
+a variable with automatic storage duration,
+a structured binding not inhabiting a namespace scope,
+the variable introduced by an \grammarterm{init-capture}, or
+a non-static data member.
+
+\recommended
+Implementations should not emit a warning
+that a name-independent declaration is used or unused.
+
 \pnum
 \indextext{declaration!potentially conflict}%
 Two declarations \defn{potentially conflict}
 if they correspond and
 cause their shared name to denote different entities\iref{basic.link}.
 The program is ill-formed
-if, in any scope, a name is bound to two declarations
-that potentially conflict and one precedes the other\iref{basic.lookup}.
+if, in any scope, a name is bound to two declarations $A$ and $B$
+that potentially conflict and $A$ precedes $B$\iref{basic.lookup},
+unless $B$ is name-independent.
+\begin{note}
+An \grammarterm{id-expression} that names a unique name-independent declaration
+is usable until an additional declaration of the same name
+is introduced in the same scope\iref{basic.lookup.general}.
+\end{note}
 \begin{note}
 Overload resolution can consider potentially conflicting declarations
 found in multiple scopes
@@ -1015,6 +1033,18 @@
 namespace B = B;        // OK, no effect
 namespace A = B;        // OK, no effect
 namespace B {}          // error: different entity for \tcode{B}
+
+void g() {
+  int _;
+  _ = 0;                // OK
+  int _;                // OK, name-independent declaration
+  _ = 0;                // error: two non-function declarations in the lookup set
+}
+void h () {
+  int _;                // \#1
+  _ ++;                 // OK
+  static int _;         // error: conflicts with \#1 because static variables are not name-independent
+}
 \end{codeblock}
 \end{example}
 
@@ -1236,7 +1266,9 @@
 \end{example}
 
 \pnum
-If a declaration whose target scope is the block scope $S$ of a
+If a declaration
+that is not a name-independent declaration and
+whose target scope is the block scope $S$ of a
 \begin{itemize}
 \item
 \grammarterm{compound-statement} of a \grammarterm{lambda-expression},
@@ -2728,6 +2760,7 @@
 for linkage purposes, if any\iref{dcl.typedef,dcl.enum},
 they correspond\iref{basic.scope.scope},
 have the same target scope that is not a function or template parameter scope,
+neither is a name-independent declaration,
 and either
 \begin{itemize}
 \item
diff --git a/source/declarations.tex b/source/declarations.tex
index 58962c889a..15c6dc71e5 100644
--- a/source/declarations.tex
+++ b/source/declarations.tex
@@ -8055,9 +8055,21 @@
 
 \pnum
 If a declaration named by a \grammarterm{using-declaration}
-that inhabits the target scope of another declaration
+that inhabits the target scope of another declaration $B$
 potentially conflicts with it\iref{basic.scope.scope}, and
-either is reachable from the other, the program is ill-formed.
+either is reachable from the other, the program is ill-formed
+unless $B$ is name-independent and
+the \grammarterm{using-declaration} precedes $B$.
+\begin{example}
+\begin{codeblock}
+int _;
+void f() {
+  int _;                // B
+  _ = 0;
+  using ::_;            // error: \grammarterm{using-declaration} does not precede B
+}
+\end{codeblock}
+\end{example}
 If two declarations named by \grammarterm{using-declaration}s
 that inhabit the same scope potentially conflict,
 either is reachable from the other, and
diff --git a/source/preprocessor.tex b/source/preprocessor.tex
index 23f2fe9bbf..c0e21559f9 100644
--- a/source/preprocessor.tex
+++ b/source/preprocessor.tex
@@ -1849,6 +1849,7 @@
 \defnxname{cpp_nontype_template_args}             & \tcode{201911L} \\ \rowsep
 \defnxname{cpp_nontype_template_parameter_auto}   & \tcode{201606L} \\ \rowsep
 \defnxname{cpp_nsdmi}                             & \tcode{200809L} \\ \rowsep
+\defnxname{cpp_placeholder_variables}             & \tcode{202306L} \\ \rowsep
 \defnxname{cpp_range_based_for}                   & \tcode{202211L} \\ \rowsep
 \defnxname{cpp_raw_strings}                       & \tcode{200710L} \\ \rowsep
 \defnxname{cpp_ref_qualifiers}                    & \tcode{200710L} \\ \rowsep

From d9c8933328cfb4a057fb45f0b615b85b6a0756b1 Mon Sep 17 00:00:00 2001
From: Jens Maurer <Jens.Maurer@gmx.net>
Date: Tue, 20 Jun 2023 08:37:56 +0200
Subject: [PATCH 2/2] [basic.scope.scope] Add Unicode name for underscore

---
 source/basic.tex | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/source/basic.tex b/source/basic.tex
index a87a7bdb73..4ba58bb4e7 100644
--- a/source/basic.tex
+++ b/source/basic.tex
@@ -989,7 +989,7 @@
 
 \pnum
 A declaration is \defnx{name-independent}{declaration!name-independent}
-if its name is \tcode{_} and it declares
+if its name is \tcode{_} (\unicode{005f}{low line}) and it declares
 a variable with automatic storage duration,
 a structured binding not inhabiting a namespace scope,
 the variable introduced by an \grammarterm{init-capture}, or