Issue with CHAR column and "column LIKE column" condition

Hi everyone,

I was surprised by the behavior of LIKE and the CHAR type. Consider
the following statements:

CREATE TABLE t0(c0 CHAR(2)) ;
INSERT INTO t0(c0) VALUES('a');
SELECT * FROM t0 WHERE c0 LIKE c0; -- expected: fetches the row,
actual: does not fetch the row

According to the docs, CHAR values are padded, and the padding is
supposed to be semantically significant in "LIKE and regular
expressions" [1], which is why I would expect the query to be
equivalent to the following:

SELECT * FROM t0 WHERE 'a ' LIKE 'a '; -- fetches the row

It seems that the trailing spaces on the right hand side are
disregarded, but not on the left hand side:

SELECT 'a' LIKE c0 FROM t0; -- unexpected: TRUE
SELECT 'a ' LIKE c0 FROM t0; -- unexpected: FALSE
SELECT c0 LIKE 'a' FROM t0; -- FALSE
SELECT c0 LIKE 'a ' FROM t0; -- TRUE

Is this behavior expected or is this a bug? By the way, this is unlike
what happens in MySQL and SQLite3, where the row would be fetched.

[1] https://www.postgresql.org/docs/11/datatype-character.html

Best,
Manuel