compiler: don't name type descriptor for alias type

The test case is https://golang.org/cl/275632.

Change-Id: Ibbbdc84f0e2151fb938de8fea7021be8cd26c703
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/275652
Trust: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

go/names.cc

diff --git a/go/names.cc b/go/names.cc
index 0097417..8e73e5e 100644
--- a/go/names.cc
+++ b/go/names.cc
@@ -1017,7 +1017,7 @@
   bool is_pointer = false;
   if (nt == NULL && type->points_to() != NULL)
     {
-      nt = type->points_to()->named_type();
+      nt = type->points_to()->unalias()->named_type();
       is_pointer = true;
     }