[C++ PATCH] Fix deprecated attribute handling on templates (PR c++/93228)

[Jakub Jelinek]

Hi!

As the following testcase shows, when deprecated attribute is on a template,
we'd never print the message if any, because the attribute is not
present on the TEMPLATE_DECL with which warn_deprecated_use is called,
but on its DECL_TEMPLATE_RESULT or its type.

Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
trunk?

2020-01-10  Jakub Jelinek  <jakub@redhat.com>

	PR c++/93228
	* parser.c (cp_parser_template_name): Look up deprecated attribute
	in DECL_TEMPLATE_RESULT or its type's attributes.

	* g++.dg/cpp1y/attr-deprecated-3.C: New test.

--- gcc/cp/parser.c.jj	2020-01-10 17:52:48.084062620 +0100
+++ gcc/cp/parser.c	2020-01-10 19:15:29.019861630 +0100
@@ -16882,7 +16882,17 @@ cp_parser_template_name (cp_parser* pars
     {
       if (TREE_DEPRECATED (decl)
 	  && deprecated_state != DEPRECATED_SUPPRESS)
-	warn_deprecated_use (decl, NULL_TREE);
+	{
+	  tree d = DECL_TEMPLATE_RESULT (decl);
+	  tree attr;
+	  if (TREE_CODE (d) == TYPE_DECL)
+	    attr = lookup_attribute ("deprecated",
+				     TYPE_ATTRIBUTES (TREE_TYPE (d)));
+	  else
+	    attr = lookup_attribute ("deprecated",
+				     DECL_ATTRIBUTES (d));
+	  warn_deprecated_use (decl, attr);
+	}
     }
   else
     {
--- gcc/testsuite/g++.dg/cpp1y/attr-deprecated-3.C.jj	2020-01-10 19:20:44.165196267 +0100
+++ gcc/testsuite/g++.dg/cpp1y/attr-deprecated-3.C	2020-01-10 19:20:48.699129148 +0100
@@ -0,0 +1,13 @@
+// PR c++/93228
+// { dg-do compile { target c++14 } }
+
+template <typename T>
+struct [[deprecated("foo")]] bar {};	// { dg-message "declared here" }
+struct [[deprecated("baz")]] qux {}; 	// { dg-message "declared here" }
+
+void
+quux ()
+{
+  bar<int> b;	// { dg-warning "is deprecated: foo" }
+  qux c;	// { dg-warning "is deprecated: baz" }
+}

	Jakub