Unable parse a comment in gram.y

I was unable to parse a comment in src/backend/parser/gram.y around line 11364:

/*
 * As func_expr but does not accept WINDOW functions directly (they
 * can still be contained in arguments for functions etc.)
 * Use this when window expressions are not allowed, so to disambiguate
 * the grammar. (e.g. in CREATE INDEX)
 */

Maybe "but" is unnecessary in the first sentence in the comment?

Best reagards,
--
Tatsuo Ishii
SRA OSS LLC
English: http://www.sraoss.co.jp/index_en/
Japanese:http://www.sraoss.co.jp