proof concept: do statement parametrization

Hello

I enhanced DO statement syntax to allowing a parameters. Syntax is
relative simple:

do ([varname] vartype := value, ...) $$ ... $$

It allows to pass a content of psql variables to inline code block to
allows more easy scripting

\set schema 'public'

do(text := :'schema') $$
declare r record;
begin
  for r in
      select * from information_schema.tables where table_schema = $1
  loop
    raise notice '>>> table %', r.table_name;
  end loop;
end $$;
NOTICE:  >>> table t
NOTICE:  >>> table t1
DO

ToDo:

* doesn't allows SubLinks :(

pavel@postgres:5432=# do(text := (SELECT :'schema')) $$ declare r
record; begin for r in select * from information_schema.tables where
table_schema = $1 loop raise notice '>>> table %', r.table_name; end
loop; end $$;
ERROR:  XX000: unrecognized node type: 315
LOCATION:  ExecInitExpr, execQual.c:4868

ideas, notes, comments??

Regards

Pavel Stehule