Bryn Llewellyn <bryn(at)yugabyte(dot)com> writes:
> The DO block runs without error and reports "INFO: 42". This is an unambiguous semantic error because "a" is declared "constant".
> Is this a known issue?
It is, see
https://git.postgresql.org/gitweb/?p=postgresql.git&a=commitdiff&h=ccd10a9bf
regards, tom lane