From: "nobu (Nobuyoshi Nakada) via ruby-core" <ruby-core@...>
Date: 2025-06-24T06:56:16+00:00
Subject: [ruby-core:122590] [Ruby Bug#21450] Inconsistent `upcase` between `String` and `Symbol`

Issue #21450 has been updated by 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 a symbol, `:i`, that contains ASCII 7bit characters only is US-ASCII.

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

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

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


----------------------------------------
Bug #21450: Inconsistent `upcase` between `String` and `Symbol`
https://bugs.ruby-lang.org/issues/21450#change-113825

* Author: Stranger6667 (Dmitry Dygalo)
* Status: Closed
* ruby -v: 3.4
* Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN
----------------------------------------
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:

```ruby
'i'.upcase(:turkic)
# "��"   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`:


```ruby
:i��.upcase(:turkic)
# :����   # with dot
'i��'.upcase(:turkic)
# "����"  # with dot 

```



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