Improve error for undefined name in imported package.

Avoid emitting some followon errors.

From-SVN: r179020

gcc/go/gofrontend/expressions.cc

@@ -9730,7 +9730,10 @@ Call_result_expression::do_type()
   if (fntype == NULL)
     {
       if (ce->issue_error())
+	{
+	  if (!ce->fn()->type()->is_error())
 	    this->report_error(_("expected function"));
+	}
       this->set_is_error();
       return Type::make_error_type();
     }
@@ -10043,7 +10046,9 @@ Array_index_expression::do_check_types(Gogo*)
     this->report_error(_("index must be integer"));
   if (this->end_ != NULL
       && this->end_->type()->integer_type() == NULL
-      && !this->end_->is_nil_expression())
+      && !this->end_->type()->is_error()
+      && !this->end_->is_nil_expression()
+      && !this->end_->is_error_expression())
     this->report_error(_("slice end must be integer"));
 
   Array_type* array_type = this->array_->type()->array_type();

gcc/go/gofrontend/parse.cc

@@ -335,10 +335,17 @@ Parse::type_name(bool issue_error)
   bool ok = true;
   if (named_object == NULL)
     {
-      if (package != NULL)
-	ok = false;
-      else
+      if (package == NULL)
 	named_object = this->gogo_->add_unknown_name(name, location);
+      else
+	{
+	  const std::string& packname(package->package_value()->name());
+	  error_at(location, "reference to undefined identifer %<%s.%s%>",
+		   Gogo::message_name(packname).c_str(),
+		   Gogo::message_name(name).c_str());
+	  issue_error = false;
+	  ok = false;
+	}
     }
   else if (named_object->is_type())
     {