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* [PATCH] c++: Fix up parameter pack diagnostics on xobj vs. varargs functions [PR113802]
@ 2024-02-16  9:03 Jakub Jelinek
  2024-02-16 20:47 ` Jason Merrill
  0 siblings, 1 reply; 6+ messages in thread
From: Jakub Jelinek @ 2024-02-16  9:03 UTC (permalink / raw)
  To: Jason Merrill; +Cc: gcc-patches

Hi!

The simple presence of ellipsis as next token after the parameter
declaration doesn't imply it is a parameter pack, it sometimes is, e.g.
if its type is a pack, but sometimes is not and in that case it acts
the same as if the next tokens were , ... instead of just ...
The xobj param cannot be a function parameter pack though treats both
the declarator->parameter_pack_p and token->type == CPP_ELLIPSIS as
sufficient conditions for the error.  The conditions for CPP_ELLIPSIS
are done a little bit later in the same function and complex enough that
IMHO shouldn't be repeated, on the other side for the
declarator->parameter_pack_p case we clear that flag for xobj params
for error recovery reasons.
In order to avoid diagnosing this in two spots, one at the current spot
for declarator->parameter_pack_p and one for the ellipsis case after
we decide if it is parameter pack or varargs, the following patch instead
just sets a boolean flag whether we should emit this diagnostics, does it
early for declarator->parameter_pack_p case and clears the parameter_pack_p
flag in that case like the older patch did, and for the ellipsis case
sets the flag later, then emits the diagnostics.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2024-02-16  Jakub Jelinek  <jakub@redhat.com>

	PR c++/113802
	* parser.cc (cp_parser_parameter_declaration): Don't emit
	PR113307 diagnostics too early, instead for the
	declarator->parameter_pack_p case just set a flag it should be emitted
	later.  Set that flag also when consuming following ellipsis as part
	of a parameter pack and diagnose either afterwards.  Formatting fix.

	* g++.dg/cpp23/explicit-obj-diagnostics3.C (S0, S1, S2, S3, S4): Don't
	expect any diagnostics on f and fd member function templates, add
	similar templates with ...Selves instead of Selves as k and kd and
	expect diagnostics for those.

--- gcc/cp/parser.cc.jj	2024-02-14 14:26:19.000000000 +0100
+++ gcc/cp/parser.cc	2024-02-15 11:58:27.033618967 +0100
@@ -25727,17 +25727,10 @@ cp_parser_parameter_declaration (cp_pars
   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)))
+  bool diag_xobj_parameter_pack = false;
+  if (xobj_param_p && (declarator && declarator->parameter_pack_p))
     {
-      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");
+      diag_xobj_parameter_pack = true;
       /* Suppress errors that occur down the line.  */
       if (declarator)
 	declarator->parameter_pack_p = false;
@@ -25755,9 +25748,10 @@ cp_parser_parameter_declaration (cp_pars
 	(INNERMOST_TEMPLATE_PARMS (current_template_parms));
 
       if (latest_template_parm_idx != template_parm_idx)
-	decl_specifiers.type = convert_generic_types_to_packs
-	  (decl_specifiers.type,
-	   template_parm_idx, latest_template_parm_idx);
+	decl_specifiers.type
+	  = convert_generic_types_to_packs (decl_specifiers.type,
+					    template_parm_idx,
+					    latest_template_parm_idx);
     }
 
   if (cp_lexer_next_token_is (parser->lexer, CPP_ELLIPSIS))
@@ -25773,6 +25767,8 @@ cp_parser_parameter_declaration (cp_pars
 	   || (!type && template_parm_p))
 	  && declarator_can_be_parameter_pack (declarator))
 	{
+	  if (xobj_param_p)
+	    diag_xobj_parameter_pack = true;
 	  /* Consume the `...'. */
 	  cp_lexer_consume_token (parser->lexer);
 	  maybe_warn_variadic_templates ();
@@ -25787,6 +25783,17 @@ cp_parser_parameter_declaration (cp_pars
 	}
     }
 
+  if (diag_xobj_parameter_pack)
+    {
+      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");
+    }
+
   /* The restriction on defining new types applies only to the type
      of the parameter, not to the default argument.  */
   parser->type_definition_forbidden_message = saved_message;
--- gcc/testsuite/g++.dg/cpp23/explicit-obj-diagnostics3.C.jj	2024-01-17 10:34:49.812597960 +0100
+++ gcc/testsuite/g++.dg/cpp23/explicit-obj-diagnostics3.C	2024-02-15 12:14:29.994356800 +0100
@@ -24,7 +24,7 @@ void S::f12(this S s = {}) {} // { dg-er
 
 struct S0 {
   template<typename Selves>
-  void f(this Selves...) {} // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+  void f(this Selves...) {}
 
   template<typename Selves>
   void g(this Selves... selves) {}  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
@@ -32,19 +32,25 @@ struct S0 {
   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 k(this 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" }
+  void fd(this Selves...);
 
   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" }
+
+  template<typename ...Selves>
+  void kd(this 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" }
+  void f(this Selves&...) {}
 
   template<typename Selves>
   void g(this Selves&... selves) {}  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
@@ -52,19 +58,25 @@ struct S1 {
   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 k(this 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" }
+  void fd(this Selves&...);
 
   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" }
+
+  template<typename ...Selves>
+  void kd(this 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" }
+  void f(this Selves&&...) {}
 
   template<typename Selves>
   void g(this Selves&&... selves) {}  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
@@ -72,19 +84,25 @@ struct S2 {
   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 k(this 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" }
+  void fd(this Selves&&...);
 
   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" }
+
+  template<typename ...Selves>
+  void kd(this 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" }
+  void f(this Selves const&...) {}
 
   template<typename Selves>
   void g(this Selves const&... selves) {}  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
@@ -92,19 +110,25 @@ struct S3 {
   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 k(this Selves const&...) {}  // { 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" }
+  void fd(this Selves const&...);
 
   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" }
+
+  template<typename ...Selves>
+  void kd(this Selves const&...);  // { 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" }
+  void f(this Selves const&&...) {}
 
   template<typename Selves>
   void g(this Selves const&&... selves) {}  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
@@ -112,13 +136,18 @@ struct S4 {
   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 k(this Selves const&&...) {}  // { 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" }
+  void fd(this Selves const&&...);
 
   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" }
-};
 
+  template<typename ...Selves>
+  void kd(this Selves const&&...);  // { dg-error "an explicit object parameter cannot be a function parameter pack" }
+};

	Jakub


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2024-02-16  9:03 [PATCH] c++: Fix up parameter pack diagnostics on xobj vs. varargs functions [PR113802] Jakub Jelinek
2024-02-16 20:47 ` Jason Merrill
2024-02-16 21:20   ` Jakub Jelinek
2024-02-16 21:47     ` Jakub Jelinek
2024-02-16 22:15       ` Jakub Jelinek
2024-03-06 23:43         ` Jason Merrill

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