test a = a b: undetected error

[McDutchie]

In https://bugs.debian.org/1068340, Vincent Lefevre reports:

Package: ksh93u+m
Version: 1.0.8-1
Severity: normal

$ test a = a b ; echo $?
0

while this should be an error.

Further discussion (thread): https://www.mail-archive.com/austin-group-l@opengroup.org/msg12484.html

[McDutchie]

The behaviour is identical in the original Bourne shell (tested /bin/sh on Solaris 9) and on ksh88.

[vinc17fr]

However, it could have been just a missing test for error (i.e. possibly a bug unknown at that time). Or was this done on purpose and documented? Or at least a case that was checked in the testsuite? And are there scripts that expect this behavior? I could imagine that after the equal, one may have something with a * character to perform an expansion (globbing), so that the test would be done against the first expanded word.