Bug #21450: Inconsistent `upcase` between `String` and `Symbol`

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: 3.4
• Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN

[Stranger6667 (Dmitry Dygalo)]

Behavior for Symbol#upcase and String#upcase differs for i character if the :turkic option is present

I'd expect val.upcase(:turkic) behaves consistently for both cases:

'i'.upcase(:turkic)
# "İ"   with dot
:i.upcase(:turkic)
# :I    no dot

However, when a non-ASCII character is present, then the case mapping on Symbol works the same way as with String:

:iФ.upcase(:turkic)
# :İФ   # with dot
'iФ'.upcase(:turkic)
# "İФ"  # with dot 

[Stranger6667 (Dmitry Dygalo)]

• Description updated (diff)

[Stranger6667 (Dmitry Dygalo)]

• Description updated (diff)

[nobu (Nobuyoshi Nakada)]

• Status changed from Open to Closed

That difference is because of the difference of encodings.

The string "i" is UTF-8, even it contains ASCII 7bit characters only, because the source encoding is defaulted to UTF-8.
On the other hand, the encoding of :i, the symbol that contains ASCII 7bit characters only is US-ASCII.

"i".encoding #=> #<Encoding:UTF-8>
:i.encoding  #=> #<Encoding:US-ASCII>

The string in US-ASCII does the same behavior as the symbol.

"i".encode("us-ascii").upcase(:turkic) #=> "I"