[gcc r9-9548] c++: base template friend [PR52625]

[Jason Merrill <jason@gcc.gnu.org>]

https://gcc.gnu.org/g:5b4cb06374890f2a190c9a989b569a9a15388445

commit r9-9548-g5b4cb06374890f2a190c9a989b569a9a15388445
Author: Jason Merrill <jason@redhat.com>
Date:   Wed Apr 7 15:38:07 2021 -0400

    c++: base template friend [PR52625]
    
    Here we were mistakenly treating the injected-class-name as a partial
    specialization.
    
    gcc/cp/ChangeLog:
    
            PR c++/52625
            * pt.c (maybe_process_partial_specialization): Check
            DECL_SELF_REFERENCE_P.
    
    gcc/testsuite/ChangeLog:
    
            PR c++/52625
            * g++.dg/template/friend70.C: New test.

Diff:
---
 gcc/cp/pt.c                              | 4 ++++
 gcc/testsuite/g++.dg/template/friend70.C | 9 +++++++++
 2 files changed, 13 insertions(+)

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index d0bea4a5266..20bc198efac 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -969,6 +969,10 @@ maybe_process_partial_specialization (tree type)
   if (CLASS_TYPE_P (type) && CLASSTYPE_LAMBDA_EXPR (type))
     return type;
 
+  /* An injected-class-name is not a specialization.  */
+  if (DECL_SELF_REFERENCE_P (TYPE_NAME (type)))
+    return type;
+
   if (TREE_CODE (type) == BOUND_TEMPLATE_TEMPLATE_PARM)
     {
       error ("name of class shadows template template parameter %qD",
diff --git a/gcc/testsuite/g++.dg/template/friend70.C b/gcc/testsuite/g++.dg/template/friend70.C
new file mode 100644
index 00000000000..54965486f79
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/friend70.C
@@ -0,0 +1,9 @@
+// PR c++/52625
+
+template<class>
+class base {};
+
+class derived : public base<derived>
+{
+  template<class> friend class base;
+};