BUG #13652: Function names as a table prefiex by underscore, confused with array

The following bug has been logged on the website:

Bug reference:      13652
Logged by:          Maris Radu
Email address:      marisradu@gmail.com
PostgreSQL version: 9.4.4
Operating system:   Ubuntu Server 14.04.1
Description:

Creating a method "_c()" as:
create or replace function _c(text) returns text as $$
    select $1;
$$ language sql immutable;

and a table "c" as:
create table c (id int);

Select by _c(text) returns unexpected error:

# select _c('text');
ERROR:  malformed array literal: "text"
LINE 1: select _c('text');
                  ^
DETAIL:  Array value must start with "{" or dimension information.


Dropping the table or renaming the function to solves the issue.

Expecting: The query to run normally, or an error when creating the function
or the table if the function was defined first.