Go patch committed: Fix spurious redefinition error

[Ian Lance Taylor]

This patch to the Go frontend by Than McIntosh changes
Struct_type::do_mangled_name to incorporate the field names even for
hidden symbols. This is needed in cases where a package imports a type
"S" that has an anonymous struct, e.g.

  // imported from some other package
  type S struct {
    X struct{ _ struct{} }
  }

and then defines a local type that uses a structurally identical
anonymous struct, e.g.

  // defined locally
  type T struct {
    U struct{ _ struct{} }
  }

In the case above both types triggered the creation of hash/equal
methods, but the method names were clashing (since both structs had
the same mangled name).

This fixes https://golang.org/issue/18414.

Bootstrapped and ran Go testsuite on x86_64-pc-linux-gnu.  Committed
to mainline.

Ian

Index: gcc/go/gofrontend/MERGE
===================================================================
--- gcc/go/gofrontend/MERGE     (revision 243805)
+++ gcc/go/gofrontend/MERGE     (working copy)
@@ -1,4 +1,4 @@
-4a0bb435bbb1d1516b486d1998e8dc184576db61
+9a89f32811e6b3a29e22dda46e9c23811f562876
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.
Index: gcc/go/gofrontend/gogo.h
===================================================================
--- gcc/go/gofrontend/gogo.h    (revision 243766)
+++ gcc/go/gofrontend/gogo.h    (working copy)
@@ -202,6 +202,27 @@ class Gogo
   }
 
   // Given a name which may or may not have been hidden, return the
+  // name to use within a mangled symbol name.
+  static std::string
+  mangle_possibly_hidden_name(const std::string& name)
+  { 
+    // FIXME: This adds in pkgpath twice for hidden symbols, which is
+    // less than ideal.
+    std::string n;
+    if (!Gogo::is_hidden_name(name))
+      n = name;
+    else
+      {
+        n = ".";
+        std::string pkgpath = Gogo::hidden_name_pkgpath(name);
+        n.append(Gogo::pkgpath_for_symbol(pkgpath));
+        n.append(1, '.');
+        n.append(Gogo::unpack_hidden_name(name));
+      }
+    return n;
+  }
+
+  // Given a name which may or may not have been hidden, return the
   // name to use in an error message.
   static std::string
   message_name(const std::string& name);
Index: gcc/go/gofrontend/types.cc
===================================================================
--- gcc/go/gofrontend/types.cc  (revision 243735)
+++ gcc/go/gofrontend/types.cc  (working copy)
@@ -1337,18 +1337,8 @@ Type::type_descriptor_var_name(Gogo* gog
        }
     }
 
-  // FIXME: This adds in pkgpath twice for hidden symbols, which is
-  // pointless.
-  const std::string& name(no->name());
-  if (!Gogo::is_hidden_name(name))
-    ret.append(name);
-  else
-    {
-      ret.append(1, '.');
-      ret.append(Gogo::pkgpath_for_symbol(Gogo::hidden_name_pkgpath(name)));
-      ret.append(1, '.');
-      ret.append(Gogo::unpack_hidden_name(name));
-    }
+  std::string mname(Gogo::mangle_possibly_hidden_name(no->name()));
+  ret.append(mname);
 
   return ret;
 }
@@ -5638,8 +5628,9 @@ Struct_type::do_mangled_name(Gogo* gogo,
          if (p->is_anonymous())
            ret->append("0_");
          else
-           {
-             std::string n = Gogo::unpack_hidden_name(p->field_name());
+            {
+
+              std::string 
n(Gogo::mangle_possibly_hidden_name(p->field_name()));
              char buf[20];
              snprintf(buf, sizeof buf, "%u_",
                       static_cast<unsigned int>(n.length()));
@@ -8712,17 +8703,7 @@ Interface_type::do_mangled_name(Gogo* go
        {
          if (!p->name().empty())
            {
-             std::string n;
-             if (!Gogo::is_hidden_name(p->name()))
-               n = p->name();
-             else
-               {
-                 n = ".";
-                 std::string pkgpath = Gogo::hidden_name_pkgpath(p->name());
-                 n.append(Gogo::pkgpath_for_symbol(pkgpath));
-                 n.append(1, '.');
-                 n.append(Gogo::unpack_hidden_name(p->name()));
-               }
+             std::string n(Gogo::mangle_possibly_hidden_name(p->name()));
              char buf[20];
              snprintf(buf, sizeof buf, "%u_",
                       static_cast<unsigned int>(n.length()));