c++: P0847R7 (deducing this) - diagnostics. [PR102609]

Diagnostics for xobj member functions. Also includes some diagnostics for
xobj lambdas which are not implemented here. CWG2554 is also implemented
here, we explicitly error when an xobj member function overrides a virtual
function.

	PR c++/102609

gcc/c-family/ChangeLog:

	PR c++/102609
	C++23 P0847R7 (deducing this) - diagnostics.
	* c-cppbuiltin.cc (c_cpp_builtins): Define
	__cpp_explicit_this_parameter=202110L feature test macro.

gcc/cp/ChangeLog:

	PR c++/102609
	C++23 P0847R7 (deducing this) - diagnostics.
	* class.cc (resolve_address_of_overloaded_function): Diagnostics.
	* cp-tree.h (TFF_XOBJ_FUNC): Define.
	* decl.cc (grokfndecl): Diagnostics.
	(grokdeclarator): Diagnostics.
	* error.cc (dump_aggr_type): Pass TFF_XOBJ_FUNC.
	(dump_lambda_function): Formatting for xobj lambda.
	(dump_function_decl): Pass TFF_XOBJ_FUNC.
	(dump_parameters): Formatting for xobj member functions.
	(function_category): Formatting for xobj member functions.
	* parser.cc (cp_parser_decl_specifier_seq): Diagnostics.
	(cp_parser_parameter_declaration): Diagnostics.
	* search.cc (look_for_overrides_here): Make xobj member functions
	override.
	(look_for_overrides_r): Reject an overriding xobj member function
	and diagnose it.
	* semantics.cc (finish_this_expr): Diagnostics.
	* typeck.cc (cp_build_addr_expr_1): Diagnostics.

gcc/testsuite/ChangeLog:

	PR c++/102609
	C++23 P0847R7 (deducing this) - diagnostics.
	* g++.dg/cpp23/feat-cxx2b.C: Test existance and value of
	__cpp_explicit_this_parameter feature test macro.
	* g++.dg/cpp26/feat-cxx26.C: Likewise.
	* g++.dg/cpp23/explicit-obj-cxx-dialect-A.C: New test.
	* g++.dg/cpp23/explicit-obj-cxx-dialect-B.C: New test.
	* g++.dg/cpp23/explicit-obj-cxx-dialect-C.C: New test.
	* g++.dg/cpp23/explicit-obj-cxx-dialect-D.C: New test.
	* g++.dg/cpp23/explicit-obj-cxx-dialect-E.C: New test.
	* g++.dg/cpp23/explicit-obj-diagnostics1.C: New test.
	* g++.dg/cpp23/explicit-obj-diagnostics2.C: New test.
	* g++.dg/cpp23/explicit-obj-diagnostics3.C: New test.
	* g++.dg/cpp23/explicit-obj-diagnostics4.C: New test.
	* g++.dg/cpp23/explicit-obj-diagnostics5.C: New test.
	* g++.dg/cpp23/explicit-obj-diagnostics6.C: New test.
	* g++.dg/cpp23/explicit-obj-diagnostics7.C: New test.

Signed-off-by: Waffl3x <waffl3x@protonmail.com>

1 files changed, 18 insertions, 6 deletions

diff --git a/gcc/cp/error.cc b/gcc/cp/error.cc
index a384f62..52e24fb 100644
--- a/gcc/cp/error.cc
+++ b/gcc/cp/error.cc
@@ -840,10 +840,14 @@ dump_aggr_type (cxx_pretty_printer *pp, tree t, int flags)
     {
       /* A lambda's "type" is essentially its signature.  */
       pp_string (pp, M_("<lambda"));
-      if (lambda_function (t))
-	dump_parameters (pp,
-                         FUNCTION_FIRST_USER_PARMTYPE (lambda_function (t)),
-			 flags);
+      tree const fn = lambda_function (t);
+      if (fn)
+	{
+	  int const parm_flags
+	    = DECL_XOBJ_MEMBER_FUNCTION_P (fn) ? TFF_XOBJ_FUNC | flags
+					       : flags;
+	  dump_parameters (pp, FUNCTION_FIRST_USER_PARMTYPE (fn), parm_flags);
+	}
       pp_greater (pp);
     }
   else if (!decl || IDENTIFIER_ANON_P (DECL_NAME (decl)))
@@ -1712,7 +1716,9 @@ dump_lambda_function (cxx_pretty_printer *pp,
 {
   /* A lambda's signature is essentially its "type".  */
   dump_type (pp, DECL_CONTEXT (fn), flags);
-  if (TREE_CODE (TREE_TYPE (fn)) == FUNCTION_TYPE)
+  if (DECL_XOBJ_MEMBER_FUNCTION_P (fn))
+    /* Early escape.  */;
+  else if (TREE_CODE (TREE_TYPE (fn)) == FUNCTION_TYPE)
     {
       pp->padding = pp_before;
       pp_c_ws_string (pp, "static");
@@ -1833,7 +1839,9 @@ dump_function_decl (cxx_pretty_printer *pp, tree t, int flags)
 
   if (!(flags & TFF_NO_FUNCTION_ARGUMENTS))
     {
-      dump_parameters (pp, parmtypes, flags);
+      int const parm_flags
+	= DECL_XOBJ_MEMBER_FUNCTION_P (t) ? TFF_XOBJ_FUNC | flags : flags;
+      dump_parameters (pp, parmtypes, parm_flags);
 
       if (TREE_CODE (fntype) == METHOD_TYPE)
 	{
@@ -1912,6 +1920,8 @@ dump_parameters (cxx_pretty_printer *pp, tree parmtypes, int flags)
   for (first = 1; parmtypes != void_list_node;
        parmtypes = TREE_CHAIN (parmtypes))
     {
+      if (first && flags & TFF_XOBJ_FUNC)
+	pp_string (pp, "this ");
       if (!first)
 	pp_separate_with_comma (pp);
       first = 0;
@@ -3696,6 +3706,8 @@ function_category (tree fn)
 	return _("In destructor %qD");
       else if (LAMBDA_FUNCTION_P (fn))
 	return _("In lambda function");
+      else if (DECL_XOBJ_MEMBER_FUNCTION_P (fn))
+	return _("In explicit object member function %qD");
       else
 	return _("In member function %qD");
     }