From 104362255134a29a6370a3f77d4433ec1ded526a Mon Sep 17 00:00:00 2001
From: Herb Sutter <herb.sutter@gmail.com>
Date: Wed, 13 Sep 2023 12:09:22 -0700
Subject: [PATCH] Allow `__identifier__keyword` to be the identifier "keyword",
 closes #642

See
---
 regression-tests/test-results/version |  2 +-
 source/build.info                     |  2 +-
 source/common.h                       |  1 +
 source/lex.h                          | 13 +++++++++++++
 source/parse.h                        |  2 +-
 5 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/regression-tests/test-results/version b/regression-tests/test-results/version
index f9603c154..3ec7b4dea 100644
--- a/regression-tests/test-results/version
+++ b/regression-tests/test-results/version
@@ -1,5 +1,5 @@
 
-cppfront compiler v0.2.1   Build 8912:1051
+cppfront compiler v0.2.1   Build 8913:1037
 Copyright(c) Herb Sutter   All rights reserved
 
 SPDX-License-Identifier: CC-BY-NC-ND-4.0
diff --git a/source/build.info b/source/build.info
index cbce88813..495b5d43f 100644
--- a/source/build.info
+++ b/source/build.info
@@ -1 +1 @@
-"8912:1051"
\ No newline at end of file
+"8913:1037"
\ No newline at end of file
diff --git a/source/common.h b/source/common.h
index a156da34b..72e455876 100644
--- a/source/common.h
+++ b/source/common.h
@@ -359,6 +359,7 @@ auto is_identifier_continue(char c)
 }
 
 //G identifier:
+//G     '__identifier__' keyword    [Note: without whitespace before the keyword]
 //G     identifier-start
 //G     identifier identifier-continue
 //G     'operator' operator
diff --git a/source/lex.h b/source/lex.h
index a458ad721..9902f346f 100644
--- a/source/lex.h
+++ b/source/lex.h
@@ -306,6 +306,16 @@ class token
         v.start(*this, depth);
     }
 
+    auto remove_prefix_if(std::string_view prefix) {
+        if (
+            sv.size() > prefix.size()
+            && sv.starts_with(prefix)
+            )
+        {
+            sv.remove_prefix(prefix.size());
+        }
+    }
+
 private:
     std::string_view sv;
     source_position  pos;
@@ -1682,6 +1692,9 @@ auto lex_line(
                     else
                     {
                         store(j, lexeme::Identifier);
+
+                        tokens.back().remove_prefix_if("__identifier__");
+
                         if (tokens.back() == "NULL") {
                             errors.emplace_back(
                                 source_position(lineno, i),
diff --git a/source/parse.h b/source/parse.h
index 914a7a9cd..fd7ddceb7 100644
--- a/source/parse.h
+++ b/source/parse.h
@@ -7106,7 +7106,7 @@ class parser
 
 
     //G declaration:
-    //G     access-specifier? identifier unnamed-declaration
+    //G     access-specifier? identifier '...'? unnamed-declaration
     //G     access-specifier? identifier alias
     //G
     //G access-specifier: