c++: Fix up access_context::current and current_namespace

On Mon, Mar 30, 2026 at 01:15:07PM +0200, Tomasz Kaminski wrote:
> > auto
> > Q::baz () -> typename [: current_namespace () == ^^Q ? ^^int : ^^:: :]
> > {
> >   return 0;
> > }
> > part also fails, there I don't know what's right but possibly it should
> > be in Q; in that case it would be a pre-existing bug already for
> > std::meta::access_context::current () too.
> >
> My reading of the standard may be wrong here.

I think you're right, but because it is a preexisting bug on
access_context, sending this as a separate patch rather than
updating the current_* patch.

2026-04-01  Jakub Jelinek  <jakub@redhat.com>

	* reflect.cc (reflect_current_scope): Use decl_namespace_list->last ()
	in preference to current_namespace.

	* g++.dg/reflect/access_context1.C: Add new tests.
	* g++.dg/reflect/current_function1.C: Likewise.
	* g++.dg/reflect/current_class1.C: Likewise.
	* g++.dg/reflect/current_class2.C: Likewise.
	* g++.dg/reflect/current_namespace1.C: Likewise.

Reviewed-by: Jason Merrill <jason@redhat.com>

Author: jakubjelinek

gcc/cp/reflect.cc

@@ -6356,6 +6356,9 @@ reflect_current_scope (location_t loc, const constexpr_ctx *ctx, tree call,
 	}
       if (current_class_type)
 	scope = current_class_type;
+      /* If we have been pushed into a different namespace, use it.  */
+      else if (!vec_safe_is_empty (decl_namespace_list))
+	scope = decl_namespace_list->last ();
       else if (current_namespace)
 	scope = current_namespace;
       else

gcc/testsuite/g++.dg/reflect/access_context1.C

@@ -146,6 +146,8 @@ namespace O
   {
     return a;
   }
+  int bar ();
+  int baz ();
 }
 
 consteval bool
@@ -156,6 +158,18 @@ can_do_via (info r)
   return true;
 }
 
+typename [: access_context::current ().scope () == ^^:: ? ^^int : ^^:: :]
+O::bar ()
+{
+  return 0;
+}
+
+auto
+O::baz () -> typename [: access_context::current ().scope () == ^^O ? ^^int : ^^:: :]
+{
+  return 0;
+}
+
 struct W;
 
 static_assert (can_do_via (^^S));

gcc/testsuite/g++.dg/reflect/current_class1.C

@@ -68,3 +68,16 @@ bar ()
     static_assert (parent_of (current_class ()) == ^^bar);
   };
 }
+
+struct X {
+  struct Y {
+    int foo ();
+  };
+};
+
+auto
+X::Y::foo ()
+-> typename [: current_class () == ^^Y ? ^^int : ^^:: :]
+{
+  return 0;
+}

gcc/testsuite/g++.dg/reflect/current_class2.C

@@ -71,3 +71,15 @@ namespace O
     return a;						// { dg-error "invalid initialization of reference of type" }
   }
 }
+
+struct X {
+  struct Y {
+    int foo ();
+  };
+};
+
+typename [: current_class () == ^^X ? ^^int : ^^:: :]	// { dg-error "uncaught exception of type 'std::meta::exception'; 'what\\\(\\\)': 'current scope does not represent a class nor a member function'" }
+X::Y::foo ()						// { dg-error "expected unqualified-id before 'typename'" "" { target *-*-* } .-1 }
+{
+  return 0;
+}

gcc/testsuite/g++.dg/reflect/current_function1.C

@@ -38,13 +38,19 @@ struct V : U
   info v = current_function ();
 };
 
+struct W : T
+{
+  info w = current_function ();
+};
+
 void
 bar ()
 {
   static_assert (current_function () == ^^bar);
   static_assert (foo (^^foo) == ^^foo);
   static_assert (foo () == ^^bar);
   static_assert (T {}.t == ^^bar);
+  static_assert (is_constructor (T ().t) && parent_of (T ().t) == ^^T);
   consteval {
     static_assert (current_function () == ^^bar);
     consteval {
@@ -74,3 +80,14 @@ baz ()
 }
 
 static_assert (baz ());
+
+consteval void
+fred ()
+{
+  constexpr W w;
+  static_assert (is_constructor (w.t) && parent_of (w.t) == ^^T);
+  static_assert (is_constructor (w.w) && parent_of (w.w) == ^^W);
+  constexpr W wb {};
+  static_assert (wb.t == ^^fred);
+  static_assert (wb.w == ^^fred);
+}

gcc/testsuite/g++.dg/reflect/current_namespace1.C

@@ -90,4 +90,19 @@ namespace Q
   {
     return a;
   }
+
+  int bar ();
+  int baz ();
+}
+
+typename [: current_namespace () == ^^:: ? ^^int : ^^:: :]
+Q::bar ()
+{
+  return 0;
+}
+
+auto
+Q::baz () -> typename [: current_namespace () == ^^Q ? ^^int : ^^:: :]
+{
+  return 0;
 }