[PR c++/84804] ICE with default arg, template friend & lambda

https://gcc.gnu.org/ml/gcc-patches/2018-03/msg01108.html
	PR c++/84804
	* name-lookup.c (do_pushtag): Permit lambdas to be pushed into
	complete classes.


	PR c++/84804
	* g++.dg/lookup/pr84804.C: New.

From-SVN: r258722

gcc/cp/ChangeLog

+2018-03-21  Nathan Sidwell  <nathan@acm.org>
+
+	PR c++/84804
+	* name-lookup.c (do_pushtag): Permit lambdas to be pushed into
+	complete classes.
+
 2018-03-21  Martin Sebor  <msebor@redhat.com>
 
 	PR c++/84850

gcc/cp/name-lookup.c

@@ -6436,7 +6436,8 @@ do_pushtag (tree name, tree type, tag_scope scope)
 
       if (b->kind == sk_class)
 	{
-	  if (!TYPE_BEING_DEFINED (current_class_type))
+	  if (!TYPE_BEING_DEFINED (current_class_type)
+	      && !LAMBDA_TYPE_P (type))
 	    return error_mark_node;
 
 	  if (!PROCESSING_REAL_TEMPLATE_DECL_P ())

gcc/testsuite/ChangeLog

+2018-03-21  Nathan Sidwell  <nathan@acm.org>
+
+	PR c++/84804
+	* g++.dg/lookup/pr84804.C: New.
+
 2018-03-21  Martin Sebor  <msebor@redhat.com>
 
 	PR c++/84850

gcc/testsuite/g++.dg/lookup/pr84804.C

+// { dg-do compile { target c++11 } }
+// PR c++/84804 ICE instantiating friend with default arg containing a lambda
+template<int> struct A
+{
+  // Note, instantiation injects this into ::, so there can only be one!
+  friend void foo(int i = []{ return 0;}()) {}
+};
+
+void bar()
+{
+  A<0> x;
+}