IN clause behaving badly with missing comma and line break

if you use IN() clause (I've tested in WHERE and CASE) and you forget comma between values, it is syntax error (correct behaviour). But if there is newline between those two values, suddenly it is not syntax error (query will run successfully), and all values are simply ignored. 

Examples:

WITH sample AS (SELECT 'c' AS t) SELECT CASE WHEN t IN ('a','b') THEN 1 WHEN t IN ('c'
  'd') THEN 2 END FROM sample;

WITH sample AS (SELECT 'c' AS t)
SELECT * FROM sample WHERE t IN ('a'
'c');