"Bug" from time immemorial with subscript flags

[Bart Schaefer <schaefer@xxxxxxxxxxxxxxxx>]

No suggested solution at the moment:

% a='three words here'
% : ${a[(w)*]}
zsh: bad math expression: operand expected at `*'

That example is a bit nonsense because (w) does not cause the result
to be returned as an array, only to be indexed differently, so there
would be no reason to use [*] (or [@]) there.  However, any subscript
flags cause the same error.