compiler: support alias to pointer type as receiver in method declaration

    
    Fixes golang/go#27994.
    
    Reviewed-on: https://go-review.googlesource.com/c/160459

From-SVN: r268450

gcc/go/gofrontend/MERGE

-2206f40fc1e0e1e2ba3eacb7388dd26b72729bde
+cbcc538adc5177778da5788d1101e16f106a1514
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

gcc/go/gofrontend/gogo.cc

@@ -2096,12 +2096,20 @@ Gogo::declare_function(const std::string& name, Function_type* type,
       // declarations.
       Type* rtype = type->receiver()->type();
 
+      while (rtype->named_type() != NULL
+	  && rtype->named_type()->is_alias())
+	rtype = rtype->named_type()->real_type()->forwarded();
+
       // We want to look through the pointer created by the
       // parser, without getting an error if the type is not yet
       // defined.
       if (rtype->classification() == Type::TYPE_POINTER)
 	rtype = rtype->points_to();
 
+      while (rtype->named_type() != NULL
+	  && rtype->named_type()->is_alias())
+	rtype = rtype->named_type()->real_type()->forwarded();
+
       if (rtype->is_error_type())
 	return NULL;
       else if (rtype->named_type() != NULL)