[PATCH] Fix PR c++/60573

[Adam Butcher <adam at jessamine dot co dot uk>]

	PR c++/60573
	* parser.c (synthesize_implicit_template_parm): Use cp_binding_level::
	class_shadowed rather than TYPE_BEING_DEFINED as the predicate for
	unwinding to class-defining scope to handle the erroneous definition of
	a generic function of an arbitrarily nested class within an enclosing
	class.

	PR c++/60573
	* g++.dg/cpp1y/pr60573.C: New testcase.
---
 gcc/cp/parser.c                      | 30 ++++++++++++++++++++++++------
 gcc/testsuite/g++.dg/cpp1y/pr60573.C | 28 ++++++++++++++++++++++++++++
 2 files changed, 52 insertions(+), 6 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp1y/pr60573.C

diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index e729d65..2130bcd 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -32000,7 +32000,7 @@ synthesize_implicit_template_parm  (cp_parser *parser)
 	{
 	  /* If not defining a class, then any class scope is a scope level in
 	     an out-of-line member definition.  In this case simply wind back
-	     beyond the first such scope to inject the template argument list.
+	     beyond the first such scope to inject the template parameter list.
 	     Otherwise wind back to the class being defined.  The latter can
 	     occur in class member friend declarations such as:
 
@@ -32011,12 +32011,30 @@ synthesize_implicit_template_parm  (cp_parser *parser)
 		 friend void A::foo (auto);
 	       };
 
-	    The template argument list synthesized for the friend declaration
-	    must be injected in the scope of 'B', just beyond the scope of 'A'
-	    introduced by 'A::'.  */
+	    The template parameter list synthesized for the friend declaration
+	    must be injected in the scope of 'B'.  This can also occur in
+	    erroneous cases such as:
 
-	  while (scope->kind == sk_class
-		 && !TYPE_BEING_DEFINED (scope->this_entity))
+	       struct A {
+	         struct B {
+		   void foo (auto);
+		 };
+		 void B::foo (auto) {}
+	       };
+
+	     Here the attempted definition of 'B::foo' within 'A' is ill-formed
+	     but, nevertheless, the template parameter list synthesized for the
+	     declarator should be injected into the scope of 'A' as if the
+	     ill-formed template was specified explicitly.
+
+	     Note: cp_binding_level::class_shadowed is used as a predicate to
+	     indicate whether a class scope is a class-defining scope.  We stop
+	     at the first such scope as this will be the currently open class
+	     definition into which the function being declared will be appended;
+	     and therefore the scope into which the synthesized template
+	     parameter list for the declarator should be injected.  */
+
+	  while (scope->kind == sk_class && !scope->class_shadowed)
 	    {
 	      parent_scope = scope;
 	      scope = scope->level_chain;
diff --git a/gcc/testsuite/g++.dg/cpp1y/pr60573.C b/gcc/testsuite/g++.dg/cpp1y/pr60573.C
new file mode 100644
index 0000000..2f60707
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/pr60573.C
@@ -0,0 +1,28 @@
+// PR c++/60573
+// { dg-do compile { target c++1y } }
+// { dg-options "" }
+
+struct A
+{
+  struct B
+  {
+    void foo(auto);
+  };
+
+  void B::foo(auto) {}  // { dg-error "cannot define" }
+
+  struct X
+  {
+    struct Y
+    {
+      struct Z
+      {
+        void foo(auto);
+      };
+    };
+
+    void Y::Z::foo(auto) {}  // { dg-error "cannot define" }
+  };
+
+  void X::Y::Z::foo(auto) {}  // { dg-error "cannot define" }
+};
-- 
1.9.0