c++: Lost deprecated/unavailable attr in class tmpl [PR104682]

When looking into the other PR I noticed that we fail to give a warning
for a deprecated enumerator when the enum is in a class template.  This
only happens when the attribute doesn't have an argument.  The reason is
that when we tsubst_enum, we create a new enumerator:

      build_enumerator (DECL_NAME (decl), value, newtag,
           DECL_ATTRIBUTES (decl), DECL_SOURCE_LOCATION (decl));

but DECL_ATTRIBUTES (decl) is null when the attribute was provided
without an argument -- in that case it simply melts into a tree flag.
handle_deprecated_attribute has:

      if (!args)
         *no_add_attrs = true;

so the attribute isn't retained and we lose it when tsubsting.  Same
thing when the attribute is on the enum itself.

Attribute unavailable is a similar case, but it's different in that
it can be a late attribute whereas "deprecated" can't:
is_late_template_attribute has

                /* But some attributes specifically apply to templates.  */
                && !is_attribute_p ("abi_tag", name)
                && !is_attribute_p ("deprecated", name)
                && !is_attribute_p ("visibility", name))
         return true;
       else
         return false;

which looks strange, but attr-unavailable-9.C tests that we don't error when
the attribute is applied on a template.

	PR c++/104682

gcc/cp/ChangeLog:

	* cp-tree.h (build_enumerator): Adjust.
	* decl.cc (finish_enum): Make it return the new decl.
	* pt.cc (tsubst_enum): Propagate TREE_DEPRECATED and TREE_UNAVAILABLE.

gcc/testsuite/ChangeLog:

	* g++.dg/ext/attr-unavailable-10.C: New test.
	* g++.dg/ext/attr-unavailable-11.C: New test.
	* g++.dg/warn/deprecated-17.C: New test.
	* g++.dg/warn/deprecated-18.C: New test.

7 files changed, 133 insertions, 6 deletions

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 37d462f..80994e9 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -6833,7 +6833,7 @@ extern void xref_basetypes			(tree, tree);
 extern tree start_enum				(tree, tree, tree, tree, bool, bool *);
 extern void finish_enum_value_list		(tree);
 extern void finish_enum				(tree);
-extern void build_enumerator			(tree, tree, tree, tree, location_t);
+extern tree build_enumerator			(tree, tree, tree, tree, location_t);
 extern tree lookup_enumerator			(tree, tree);
 extern bool start_preparsed_function		(tree, tree, int);
 extern bool start_function			(cp_decl_specifier_seq *,
diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 7b48b56..7f80f9d 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -16409,7 +16409,7 @@ finish_enum (tree enumtype)
    Apply ATTRIBUTES if available.  LOC is the location of NAME.
    Assignment of sequential values by default is handled here.  */
 
-void
+tree
 build_enumerator (tree name, tree value, tree enumtype, tree attributes,
 		  location_t loc)
 {
@@ -16611,6 +16611,8 @@ incremented enumerator value is too large for %<long%>"));
 
   /* Add this enumeration constant to the list for this type.  */
   TYPE_VALUES (enumtype) = tree_cons (name, decl, TYPE_VALUES (enumtype));
+
+  return decl;
 }
 
 /* Look for an enumerator with the given NAME within the enumeration
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 70f02db..8fb1734 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -26944,9 +26944,8 @@ tsubst_enum (tree tag, tree newtag, tree args)
   for (e = TYPE_VALUES (tag); e; e = TREE_CHAIN (e))
     {
       tree value;
-      tree decl;
+      tree decl = TREE_VALUE (e);
 
-      decl = TREE_VALUE (e);
       /* Note that in a template enum, the TREE_VALUE is the
 	 CONST_DECL, not the corresponding INTEGER_CST.  */
       value = tsubst_expr (DECL_INITIAL (decl),
@@ -26958,8 +26957,14 @@ tsubst_enum (tree tag, tree newtag, tree args)
 
       /* Actually build the enumerator itself.  Here we're assuming that
 	 enumerators can't have dependent attributes.  */
-      build_enumerator (DECL_NAME (decl), value, newtag,
-			DECL_ATTRIBUTES (decl), DECL_SOURCE_LOCATION (decl));
+      tree newdecl = build_enumerator (DECL_NAME (decl), value, newtag,
+				       DECL_ATTRIBUTES (decl),
+				       DECL_SOURCE_LOCATION (decl));
+      /* Attribute deprecated without an argument isn't sticky: it'll
+	 melt into a tree flag, so we need to propagate the flag here,
+	 since we just created a new enumerator.  */
+      TREE_DEPRECATED (newdecl) = TREE_DEPRECATED (decl);
+      TREE_UNAVAILABLE (newdecl) = TREE_UNAVAILABLE (decl);
     }
 
   if (SCOPED_ENUM_P (newtag))
@@ -26970,6 +26975,10 @@ tsubst_enum (tree tag, tree newtag, tree args)
 
   DECL_SOURCE_LOCATION (TYPE_NAME (newtag))
     = DECL_SOURCE_LOCATION (TYPE_NAME (tag));
+  TREE_DEPRECATED (newtag) = TREE_DEPRECATED (tag);
+  /* We don't need to propagate TREE_UNAVAILABLE here, because it is, unlike
+     deprecated, applied at instantiation time rather than template
+     definition time.  */
 }
 
 /* DECL is a FUNCTION_DECL that is a template specialization.  Return
diff --git a/gcc/testsuite/g++.dg/ext/attr-unavailable-10.C b/gcc/testsuite/g++.dg/ext/attr-unavailable-10.C
new file mode 100644
index 0000000..cfb9947
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/attr-unavailable-10.C
@@ -0,0 +1,22 @@
+// PR c++/104682
+// { dg-do compile { target c++11 } }
+
+template<typename>
+struct S {
+  enum E1 {
+    A __attribute__((unavailable))
+  };
+};
+
+struct S2 {
+  enum E2 {
+    A __attribute__((unavailable))
+  };
+};
+
+void
+g ()
+{
+  auto a1 = S<int>::E1::A; // { dg-error "is unavailable" }
+  auto b1 = S2::E2::A; // { dg-error "is unavailable" }
+}
diff --git a/gcc/testsuite/g++.dg/ext/attr-unavailable-11.C b/gcc/testsuite/g++.dg/ext/attr-unavailable-11.C
new file mode 100644
index 0000000..fce2452
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/attr-unavailable-11.C
@@ -0,0 +1,22 @@
+// PR c++/104682
+// { dg-do compile { target c++11 } }
+
+template<typename>
+struct S {
+  enum B {
+    A
+  } __attribute__((unavailable)) ;
+};
+
+struct S2 {
+  enum B {
+    A
+  } __attribute__((unavailable));
+};
+
+void
+g ()
+{
+  S<int>::B a1; // { dg-error "is unavailable" }
+  S2::B a2; // { dg-error "is unavailable" }
+}
diff --git a/gcc/testsuite/g++.dg/warn/deprecated-17.C b/gcc/testsuite/g++.dg/warn/deprecated-17.C
new file mode 100644
index 0000000..c4e7685
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/deprecated-17.C
@@ -0,0 +1,35 @@
+// PR c++/104682
+// { dg-do compile { target c++11 } }
+
+template<typename>
+struct S {
+  enum E1 {
+    A __attribute__((deprecated)),
+    B __attribute__((deprecated("B"))),
+    C [[deprecated]],
+    D [[deprecated("D")]]
+  };
+};
+
+struct S2 {
+  enum E2 {
+    A __attribute__((deprecated)),
+    B __attribute__((deprecated("B"))),
+    C [[deprecated]],
+    D [[deprecated("D")]]
+  };
+};
+
+void
+g ()
+{
+  auto a1 = S<int>::E1::A; // { dg-warning "is deprecated" }
+  auto a2 = S<int>::E1::B; // { dg-warning "is deprecated" }
+  auto a3 = S<int>::E1::C; // { dg-warning "is deprecated" }
+  auto a4 = S<int>::E1::D; // { dg-warning "is deprecated" }
+  
+  auto b1 = S2::A; // { dg-warning "is deprecated" }
+  auto b2 = S2::B; // { dg-warning "is deprecated" }
+  auto b3 = S2::C; // { dg-warning "is deprecated" }
+  auto b4 = S2::D; // { dg-warning "is deprecated" }
+}
diff --git a/gcc/testsuite/g++.dg/warn/deprecated-18.C b/gcc/testsuite/g++.dg/warn/deprecated-18.C
new file mode 100644
index 0000000..0d101a9
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/deprecated-18.C
@@ -0,0 +1,37 @@
+// PR c++/104682
+// { dg-do compile { target c++11 } }
+
+template<typename>
+struct S {
+  enum B {
+    A
+  } __attribute__((deprecated)) ;
+};
+
+struct S2 {
+  enum B {
+    A
+  } __attribute__((deprecated));
+};
+
+template<typename>
+struct S3 {
+  enum [[deprecated]] B {
+    A
+  };
+};
+
+struct S4 {
+  enum [[deprecated]] B {
+    A
+  };
+};
+
+void
+g ()
+{
+  S<int>::B a1; // { dg-warning "is deprecated" }
+  S2::B a2; // { dg-warning "is deprecated" }
+  S3<int>::B a3; // { dg-warning "is deprecated" }
+  S4::B a4; // { dg-warning "is deprecated" }
+}