bracket expressions and POSIX

[Clint Adams <clint@xxxxxxx>]

POSIX says that \ loses its special meaning within a bracket
expression for pattern matching and also that ! is the
^ character in that context.

So this strikes me as non-compliant:

% emulate sh
% touch \\test abc
% echo [!a]*
zsh: event not found: a]
% echo [\!a]*
\test
% echo [\]*
[]*
% echo [\\]*
\test

More specifically, the first three echoes appear to be
non-POSIX-compliant.