From 04bcc9125e0b227aa91b7bd8819d49aafddfd228 Mon Sep 17 00:00:00 2001
From: Michael Tautschnig <tautschn@amazon.com>
Date: Mon, 6 May 2024 22:32:46 +0200
Subject: [PATCH] C++ front-end: parse template parameter packs

Attach the "ellipsis" information to the declarator and not to the type.
---
 .../cpp/type_traits_essentials1/test.desc     |  2 +-
 src/cpp/cpp_declarator.h                      | 10 ++++
 src/cpp/parse.cpp                             | 51 ++++++-------------
 3 files changed, 26 insertions(+), 37 deletions(-)

diff --git a/regression/cpp/type_traits_essentials1/test.desc b/regression/cpp/type_traits_essentials1/test.desc
index 0daa9695017..3862862ffd3 100644
--- a/regression/cpp/type_traits_essentials1/test.desc
+++ b/regression/cpp/type_traits_essentials1/test.desc
@@ -1,4 +1,4 @@
-KNOWNBUG
+CORE
 main.cpp
 -std=c++11
 ^EXIT=0$
diff --git a/src/cpp/cpp_declarator.h b/src/cpp/cpp_declarator.h
index 2f62817383a..a459e73eb3f 100644
--- a/src/cpp/cpp_declarator.h
+++ b/src/cpp/cpp_declarator.h
@@ -55,6 +55,16 @@ class cpp_declaratort:public exprt
     set(ID_is_parameter, is_parameter);
   }
 
+  bool get_has_ellipsis() const
+  {
+    return get_bool(ID_ellipsis);
+  }
+
+  void set_has_ellipsis()
+  {
+    set(ID_ellipsis, true);
+  }
+
   // initializers for function arguments
   exprt &init_args()
   {
diff --git a/src/cpp/parse.cpp b/src/cpp/parse.cpp
index 641aa0ab3ab..e8cd3927613 100644
--- a/src/cpp/parse.cpp
+++ b/src/cpp/parse.cpp
@@ -1206,14 +1206,11 @@ bool Parser::rTempArgDeclaration(cpp_declarationt &declaration)
     declarator.type().make_nil();
     set_location(declarator, tk1);
 
-    bool has_ellipsis=false;
-
     if(lex.LookAhead(0)==TOK_ELLIPSIS)
     {
       cpp_tokent tk2;
       lex.get_token(tk2);
-
-      has_ellipsis=true;
+      declarator.set_has_ellipsis();
     }
 
     if(is_identifier(lex.LookAhead(0)))
@@ -1225,16 +1222,11 @@ bool Parser::rTempArgDeclaration(cpp_declarationt &declaration)
       set_location(declarator.name(), tk2);
 
       add_id(declarator.name(), new_scopet::kindt::TYPE_TEMPLATE_PARAMETER);
-
-      if(has_ellipsis)
-      {
-        // TODO
-      }
     }
 
     if(lex.LookAhead(0)=='=')
     {
-      if(has_ellipsis)
+      if(declarator.get_has_ellipsis())
         return false;
 
       typet default_type;
@@ -1307,19 +1299,16 @@ bool Parser::rTempArgDeclaration(cpp_declarationt &declaration)
               << "Parser::rTempArgDeclaration 3\n";
 #endif
 
-    bool has_ellipsis=false;
+    declaration.declarators().resize(1);
+    cpp_declaratort &declarator = declaration.declarators().front();
 
     if(lex.LookAhead(0)==TOK_ELLIPSIS)
     {
       cpp_tokent tk2;
       lex.get_token(tk2);
-
-      has_ellipsis=true;
+      declarator.set_has_ellipsis();
     }
 
-    declaration.declarators().resize(1);
-    cpp_declaratort &declarator=declaration.declarators().front();
-
     if(!rDeclarator(declarator, kArgDeclarator, true, false))
       return false;
 
@@ -1330,16 +1319,11 @@ bool Parser::rTempArgDeclaration(cpp_declarationt &declaration)
 
     add_id(declarator.name(), new_scopet::kindt::NON_TYPE_TEMPLATE_PARAMETER);
 
-    if(has_ellipsis)
-    {
-      // TODO
-    }
-
     exprt &value=declarator.value();
 
     if(lex.LookAhead(0)=='=')
     {
-      if(has_ellipsis)
+      if(declarator.get_has_ellipsis())
         return false;
 
       cpp_tokent tk;
@@ -3998,8 +3982,7 @@ bool Parser::rTemplateArgs(irept &template_args)
       if(lex.LookAhead(0)==TOK_ELLIPSIS)
       {
         lex.get_token(tk1);
-
-        // TODO
+        exp.set(ID_ellipsis, true);
       }
 #ifdef DEBUG
       std::cout << std::string(__indent, ' ') <<  "Parser::rTemplateArgs 4.2\n";
@@ -4017,13 +4000,6 @@ bool Parser::rTemplateArgs(irept &template_args)
 
       if(!rConditionalExpr(exp, true))
         return false;
-
-      if(lex.LookAhead(0)==TOK_ELLIPSIS)
-      {
-        lex.get_token(tk1);
-
-        // TODO
-      }
     }
 
 #ifdef DEBUG
@@ -5676,18 +5652,21 @@ bool Parser::rTypeNameOrFunctionType(typet &tname)
       type.parameters().push_back(parameter);
 
       t=lex.LookAhead(0);
-      if(t==',')
+      if(t == TOK_ELLIPSIS)
       {
         cpp_tokent tk;
         lex.get_token(tk);
+        to_cpp_declaration(type.parameters().back())
+          .declarators()
+          .back()
+          .set_has_ellipsis();
+        t = lex.LookAhead(0);
       }
-      else if(t==TOK_ELLIPSIS)
+
+      if(t == ',')
       {
-        // TODO -- this is actually ambiguous as it could refer to a
-        // template parameter pack or declare a variadic function
         cpp_tokent tk;
         lex.get_token(tk);
-        type.make_ellipsis();
       }
       else if(t==')')
         break;