c++: reject packs on xobj params. [PR113307]

From 9dc168e7bcbbd7d515fa28cb9cae28ec113fae0f Mon Sep 17 00:00:00 2001
From: Waffl3x <waffl3x@protonmail.com>
Date: Thu, 11 Jan 2024 14:32:46 -0700
Subject: [PATCH] c++: reject packs on xobj params. [PR113307]

Reject and diagnose xobj parameters declared as parameter packs.

	PR c++/113307

gcc/cp/ChangeLog:

	* parser.cc (cp_parser_parameter_declaration): Reject packs
	on xobj params.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp23/explicit-obj-diagnostics3.C: Add test for
	rejection of packs.

Signed-off-by: Waffl3x <waffl3x@protonmail.com>
---
 gcc/cp/parser.cc                              |  21 +++-
 .../g++.dg/cpp23/explicit-obj-diagnostics3.C  | 106 +++++++++++++++++-
 2 files changed, 125 insertions(+), 2 deletions(-)

diff --git a/gcc/cp/parser.cc b/gcc/cp/parser.cc
index 8ab98cc0c23..70fbba09bf8 100644
--- a/gcc/cp/parser.cc
+++ b/gcc/cp/parser.cc
@@ -25706,6 +25706,25 @@  cp_parser_parameter_declaration (cp_parser *parser,
      for a C-style variadic function. */
   token = cp_lexer_peek_token (parser->lexer);
 
+  bool const xobj_param_p
+    = decl_spec_seq_has_spec_p (&decl_specifiers, ds_this);
+
+  if (xobj_param_p
+      && ((declarator && declarator->parameter_pack_p)
+	  || cp_lexer_next_token_is (parser->lexer, CPP_ELLIPSIS)))
+    {
+      location_t xobj_param
+	= make_location (decl_specifiers.locations[ds_this],
+			 decl_spec_token_start->location,
+			 input_location);
+      error_at(xobj_param,
+	       "an explicit object parameter cannot "
+	       "be a function parameter pack");
+      /* Suppress errors that occur down the line.  */
+      if (declarator)
+	declarator->parameter_pack_p = false;
+    }
+
   /* If a function parameter pack was specified and an implicit template
      parameter was introduced during cp_parser_parameter_declaration,
      change any implicit parameters introduced into packs.  */
@@ -25829,7 +25848,7 @@  cp_parser_parameter_declaration (cp_parser *parser,
   if (default_argument)
     STRIP_ANY_LOCATION_WRAPPER (default_argument);
 
-  if (decl_spec_seq_has_spec_p (&decl_specifiers, ds_this))
+  if (xobj_param_p)
     {
       if (default_argument)
 	{
diff --git a/gcc/testsuite/g++.dg/cpp23/explicit-obj-diagnostics3.C b/gcc/testsuite/g++.dg/cpp23/explicit-obj-diagnostics3.C
index ec091d6ca67..304cf029f8f 100644
--- a/gcc/testsuite/g++.dg/cpp23/explicit-obj-diagnostics3.C
+++ b/gcc/testsuite/g++.dg/cpp23/explicit-obj-diagnostics3.C
@@ -1,7 +1,9 @@ 
 // P0847R7
 // { dg-do compile { target c++23 } }
 
-// rejection and diagnosis of an xobj parameter declared with a default argument
+// rejection and diagnosis of an incorrectly declared xobj parameter
+
+// default argument
 
 struct S {
   void f0(this S = {}) {} // { dg-error "an explicit object parameter may not have a default argument" }
@@ -18,3 +20,105 @@  void S::f2(this S = {}) {} // { dg-error "an explicit object parameter may not h
 void S::f11(this S s) {}
 void S::f12(this S s = {}) {} // { dg-error "an explicit object parameter may not have a default argument" }
 
+// parameter pack
+
+struct S0 {
+  template<typename Selves>
+  void f(this Selves...) {} // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+
+  template<typename Selves>
+  void g(this Selves... selves) {}  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+
+  void h(this auto...) {}  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+  void j(this auto... selves) {}  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+
+  template<typename Selves>
+  void fd(this Selves...);  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+
+  template<typename Selves>
+  void gd(this Selves... selves);  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+
+  void hd(this auto...);  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+  void jd(this auto... selves);  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+};
+
+struct S1 {
+  template<typename Selves>
+  void f(this Selves&...) {}  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+
+  template<typename Selves>
+  void g(this Selves&... selves) {}  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+
+  void h(this auto&...) {}  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+  void j(this auto&... selves) {}  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+
+  template<typename Selves>
+  void fd(this Selves&...);  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+
+  template<typename Selves>
+  void gd(this Selves&... selves);  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+
+  void hd(this auto&...);  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+  void jd(this auto&... selves);  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+};
+
+struct S2 {
+  template<typename Selves>
+  void f(this Selves&&...) {}  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+
+  template<typename Selves>
+  void g(this Selves&&... selves) {}  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+
+  void h(this auto&&...) {}  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+  void j(this auto&&... selves) {}  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+
+  template<typename Selves>
+  void fd(this Selves&&...);  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+
+  template<typename Selves>
+  void gd(this Selves&&... selves);  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+
+  void hd(this auto&&...);  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+  void jd(this auto&&... selves);  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+};
+
+struct S3 {
+  template<typename Selves>
+  void f(this Selves const&...) {}  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+
+  template<typename Selves>
+  void g(this Selves const&... selves) {}  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+
+  void h(this auto const&...) {}  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+  void j(this auto const&... selves) {}  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+
+  template<typename Selves>
+  void fd(this Selves const&...);  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+
+  template<typename Selves>
+  void gd(this Selves const&... selves);  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+
+  void hd(this auto const&...);  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+  void jd(this auto const&... selves);  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+};
+
+struct S4 {
+  template<typename Selves>
+  void f(this Selves const&&...) {}  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+
+  template<typename Selves>
+  void g(this Selves const&&... selves) {}  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+
+  void h(this auto const&&...) {}  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+  void j(this auto const&&... selves) {}  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+
+  template<typename Selves>
+  void fd(this Selves const&&...);  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+
+  template<typename Selves>
+  void gd(this Selves const&&... selves);  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+
+  void hd(this auto const&&...);  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+  void jd(this auto const&&... selves);  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+};
+
-- 
2.43.0