error on close-parenthesis in positional parameter substitution: `ksh -c 'echo "${1:+a)c}"'`

[avih]

The following:

ksh -c 'echo "${1+)}"'
ksh -c 'echo "${1+a)c}"'
ksh -c 'echo "${1:+a)b}"'

error with

syntax error at line 1: `)' unexpected

In both default and POSIX modes (--posix).

All other shells I have access to think it's fine.

No such issue with non-positional parameter. These are OK:

ksh -c 'echo "${x+)}"'
ksh -c 'echo "${x+a)c}"'
ksh -c 'echo "${x:+a)b}"'

Tested with the latest ksh93u+m release: v1.0.10 (not master), built from source on Ubuntu.

[avih]

Could anyone reproduce this issue?

[jghub]

yes I can. additionally, these remarks:

1. while "${x+)}" expands correctly, ${x+)} (w/o quotes) throws the same "`)' unexpected" syntax error as with the positional paramters
2. no problems with this construct in bash, zsh, mksh, dash
3. as a work-around, defining par=')' makes ${1+$par} expand correctly again.

[avih]

Thanks.