@var{string}. The arguments to this function (aside from
@var{nospace}) are the same as those of @code{try-completion}. Also,
this function uses @code{completion-regexp-list} in the same way that
-@code{try-completion} does. The optional argument @var{nospace} only
-matters if @var{string} is the empty string. In that case, if
-@var{nospace} is non-@code{nil}, completions that start with a space
-are ignored.
+@code{try-completion} does.
+
+The optional argument @var{nospace} is obsolete. If it is
+non-@code{nil}, completions that start with a space are ignored unless
+@var{string} starts with a space.
If @var{collection} is a function, it is called with three arguments:
@var{string}, @var{predicate} and @code{t}; then @code{all-completions}