BUG #15477: Procedure call with named inout refcursor parameter - "invalid input syntax for type boolean" error

The following bug has been logged on the website:

Bug reference: 15477
Logged by: Alexey Stepanov
Email address: stepaunov(at)gmail(dot)com
PostgreSQL version: 11.0
Operating system: RedOS (based on Red Hat Linux) (red-soft.ru)
Description:

Calling procedure with named inout refcursor parameter leads to "invalid
input syntax for type boolean" error.

Repro:
/*
select version()
PostgreSQL 11.0 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5 20150623
(Red Hat 4.8.5-28), 64-bit
*/

drop table if exists t1;
drop procedure if exists p1(integer, refcursor);

create table t1 (key serial, name text);

create or replace procedure p1(v_cnt int, v_ResultSet inout refcursor =
null)
as $$
begin
insert into t1 (name) values('name_test');
open v_ResultSet for select * from t1;
end;
$$
language plpgsql security definer
;

-- trying to call with named v_ResultSet parameter
do $$
declare
v_ResultSet refcursor;
v_cnt integer;
begin
call p1(v_cnt:=v_cnt, v_ResultSet := v_ResultSet);
raise notice '%', v_ResultSet;
end;$$
;

result (in pgAdmin3):
ERROR: invalid input syntax for type boolean: "<unnamed portal 7>"
CONTEXT: PL/pgSQL function inline_code_block line 6 at CALL
********** Error **********

ERROR: invalid input syntax for type boolean: "<unnamed portal 7>"
SQL state: 22P02
Context: PL/pgSQL function inline_code_block line 6 at CALL

-- trying to call with ordinal parameters - success!
do $$
declare
v_ResultSet refcursor;
v_cnt integer;
begin
call p1(v_cnt, v_ResultSet);
raise notice '%', v_ResultSet;
end;$$
;

result - ok