BUG #15783: Fail to select with a function in FROM clause plus another table

The following bug has been logged on the website:

Bug reference:      15783
Logged by:          To Sites
Email address:      tosites2019@gmail.com
PostgreSQL version: 10.7
Operating system:   Windows 8.1
Description:

-- FAIL
  select m.nome socio, p.tipo, sum(c.valor * m.percentual / 100) valor
  from contas_pagas('2019-04-01', '2019-04-30', 'R') c, medico m
  inner join planoconta p on (c.cod_planoconta = p.cod)
  where (m.percentual > 0)
  group by m.nome, p.tipo

  -- ERROR
  -- SQL Error [42P01]: ERROR: invalid reference to FROM-clause entry for
table "c"
  -- Hint: There is an entry for table "c", but it cannot be referenced from
this part of the query.
  -- Position: 169

  -- WORKS
  select m.nome socio, p.tipo, sum(c.valor * m.percentual / 100) valor
  from contas_pagas('2019-04-01', '2019-04-30', 'R') c
  inner join planoconta p on (c.cod_planoconta = p.cod)
  cross join medico m
  where (m.percentual > 0)
  group by m.nome, p.tipo

In other words, we need to use cross join instead of put all tables in FROM
clause, if one of these tables was a function that returns a table.