Revert 6cb12273e2 which reverted
08d48b0fff.
Issue was the support for sub-parameters (aka @param {type} foo.bar)
where the "parent" parameter was not formal (only present in a
function's docstring, but not in the function's parameters list),
subtype creation would fail to find a root parameter to attach the
sub-parameter to.
This has not actually been fixed, but for the specific case where the
formal parameters list is *completely empty* we fall back on a list of
the docstring's parameters, which works well enough for this case.
Xavier Morel
f7323dbe23