CASE with alias is not properly parsed

Feeding this SQL to the Parser:

SELECT
  CASE 
    WHEN a.kol = 1 THEN 'one'
    ELSE a.kol
  END as 'case'
FROM foo a;

will result in errors, and calling build() on the statement will result in this SQL:

SELECT CASE 'case' ELSE a.kol AS `END` END FROM foo AS `a`

The errors array contains these errors:

• An alias was previously found.
• An alias was expected.
• Unexpected keyword.
• Unexpected end of CASE expression

I encountered this problem since I upgraded from 5.8.2 to 5.9.1.

Commencez par reproduire l’expression CASE fournie via le Parser et comparez les erreurs signalées ainsi que la sortie de build(). Suivez la manière dont les expressions CASE consomment les alias et les mots-clés, puis ajoutez un cas de régression montrant que ce SQL est analysé sans erreur et que build() est généré avec l’alias correctement préservé.