C++ PATCH for c++/79580, ICE with compound literal

[Jason Merrill]

We were treating a compound literal type defined in the initializer
for a static data member as though it were a member of the class.
Fixed by ignoring classes when defining a type from within an
expression.

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

commit 23c08aed737764678bbe1af31ddaa16b2d0a4061
Author: Jason Merrill <ja...@redhat.com>
Date:   Sun Feb 19 16:50:38 2017 -0500

            PR c++/79580 - ICE with compound literal
    
            * parser.c (cp_parser_class_head): If we're in the middle of an
            expression, use ts_within_enclosing_non_class.

diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index feeafce..4656b4f 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -22771,7 +22771,10 @@ cp_parser_class_head (cp_parser* parser,
       /* If the class was unnamed, create a dummy name.  */
       if (!id)
        id = make_anon_name ();
-      type = xref_tag (class_key, id, /*tag_scope=*/ts_current,
+      tag_scope tag_scope = (parser->in_type_id_in_expr_p
+                            ? ts_within_enclosing_non_class
+                            : ts_current);
+      type = xref_tag (class_key, id, tag_scope,
                       parser->num_template_parameter_lists);
     }
 
diff --git a/gcc/testsuite/g++.dg/ext/complit15.C 
b/gcc/testsuite/g++.dg/ext/complit15.C
new file mode 100644
index 0000000..f12752d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/complit15.C
@@ -0,0 +1,8 @@
+// PR c++/79580
+// { dg-options "-flto -std=c++98" }
+
+class a
+{
+  static const double b;
+};
+const double a::b ((union { double c; }){}.c);