Issue #11859 has been updated by Martin Drst.


Some additional comments following up on the commiters' meeting yesterday:

There are many single-byte non-Unicode encodings that have case tables.

Checking the paper versions of the standards in question,  (LATIN CAPITAL LETTER A WITH GRAVE) exists in JIS X 0212-1990 at position () 10-2, and in JIS X 0213-2004 at position 9-23 on the first plane(). JIS X 0213-2004 is the version I have at hand, but that character didn't change from the -2000 version.

Checking the actual encoding of  in EUC-JP in Ruby shows the following:
```
$ ruby -e 'puts "\u00C0".encode("EUC-JP").b.inspect'
"\x8F\xAA\xA2"
```

This is clearly the JIS X 0212-1990 version, using SS3 (0x8F) to switch to the JIS X 0212 plane at G3. The 1990 version of JIS X 0212 is the first one, so the  character didn't exist in EUC-JP before.

----------------------------------------
Bug #11859: Regexp matching with \p{Upper} and \p{Lower} for EUC-JP doesnt work.
https://bugs.ruby-lang.org/issues/11859#change-59218

* Author: Kimihito Matsui
* Status: Rejected
* Priority: Normal
* Assignee: 
* ruby -v: ruby 2.2.2p95 (2015-04-13 revision 50295) [x86_64-darwin14]
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN
----------------------------------------
U+FF21 (, FULLWIDTH LATIN CAPITAL LETTER A) and U+00c0 (, LATIN CAPITAL LETTER A WITH GRAVE) is `Uppercase_Letter` so it should match and return 0 in following case but this returns 1.

~~~
ruby -e 'puts "\uFF21A".encode("EUC-JP") =~ Regexp.compile("\\\p{Upper}".encode("EUC-JP))' # => 1
ruby -e 'puts "\u00C0A".encode("EUC-JP") =~ Regexp.compile("\\\p{Upper}".encode("EUC-JP")) # => 1
~~~
This also happens in lower case matching.

~~~
ruby -e 'puts "\uFF41a".encode("EUC-JP") =~ Regexp.compile("\\\p{Lower}".encode("EUC-JP")) => 1
~~~

In Unicode encoding it works as follows.

~~~
ruby -e 'puts "\uFF21A" =~ Regexp.compile("\\\p{Upper}")'  # => 0
~~~
Looks like EUC-JP `\p{Upper}` and `\p{Lower}` regex is limited to ASCII characters.



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