This involved adding 'copy' to more generics than I hoped, but an
experiment with making it implicit showed that that way lies madness --
unless enforced, you will not remember to mark functions that don't
copy as not requiring copyable kind.
Issue #1177
trans was failing with a bounds check error because the caller
was using the declared type (an out-of-scope ty param) and not
the actual type in a list of argument types to zero.
Closes#811
