The types only optimization for callees looked at the type of the
receiver to figure out if it was a dynamic call. If the selection
involves any implicit selections, we cannot be sure that this type
is the one that will actually receive the call.
Fix by working backwards from function signature to find the true
receiver
Change-Id: If79e3de7af33480e37bcf1081abe44bb04914da4
Reviewed-on: https://go-review.googlesource.com/18563
Reviewed-by: Alan Donovan <adonovan@google.com>
ae18226edd