[pushed] tree: tweak warn_deprecated_use

[Jason Merrill via Gcc-patches]

While looking at PR90451 I noticed that this function was failing to find the
attributes if called with a variant of the struct.  And we were doing a
redundant lookup_attribute.

Tested x86_64-pc-linux-gnu, applying to trunk as obvious.

gcc/ChangeLog:

        * tree.cc (warn_deprecated_use): Look for TYPE_STUB_DECL
        on TYPE_MAIN_VARIANT.

gcc/testsuite/ChangeLog:

        * g++.dg/warn/deprecated-16.C: New test.
---
 gcc/testsuite/g++.dg/warn/deprecated-16.C | 2 ++
 gcc/tree.cc                               | 8 +++++---
 2 files changed, 7 insertions(+), 3 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/warn/deprecated-16.C

diff --git a/gcc/testsuite/g++.dg/warn/deprecated-16.C 
b/gcc/testsuite/g++.dg/warn/deprecated-16.C
new file mode 100644
index 00000000000..8d1f4191270
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/deprecated-16.C
@@ -0,0 +1,2 @@
+struct __attribute((deprecated ("foo"))) A { }; // { dg-message "declared" }
+void f(const A&) { }           // { dg-warning "deprecated: foo" }
diff --git a/gcc/tree.cc b/gcc/tree.cc
index dd919ff0717..2bbef2d6b75 100644
--- a/gcc/tree.cc
+++ b/gcc/tree.cc
@@ -12047,10 +12047,12 @@ warn_deprecated_use (tree node, tree attr)
        attr = DECL_ATTRIBUTES (node);
       else if (TYPE_P (node))
        {
-         tree decl = TYPE_STUB_DECL (node);
+         tree decl = TYPE_STUB_DECL (TYPE_MAIN_VARIANT (node));
          if (decl)
-           attr = lookup_attribute ("deprecated",
-                                    TYPE_ATTRIBUTES (TREE_TYPE (decl)));
+           {
+             node = TREE_TYPE (decl);
+             attr = TYPE_ATTRIBUTES (node);
+           }
        }
     }
 

base-commit: c352ef0ed90cfc07d494dfec111121bc683e337b
-- 
2.27.0