RFR: 8360459: UNICODE_CASE and character class with non-ASCII range does not match ASCII char [v5]

[Xueming Shen]

> Regex class should conform to **_Level 1_** of [Unicode Technical Standard #18: Unicode Regular Expressions](http://www.unicode.org/reports/tr18/), plus RL2.1 Canonical Equivalents and RL2.2 Extended Grapheme Clusters.
> 
> This PR primarily addresses conformance with RL1.5: Simple Loose Matches, which requires that simple case folding be applied to literals and (optionally) to character classes. When applied to character classes, each class is expected to be closed under simple case folding. See the standard for a detailed explanation of what it means for a class to be “**_closed_**.”
> 
> **RL1.5 states**: 
> 
> To meet this requirement, an implementation that supports case-sensitive matching should
> 
>     1. Provide at least the simple, default Unicode case-insensitive matching, and
>     2. Specify which character properties or constructs are closed under the matching.
> 
> **In the Pattern implementation**, 5 types of constructs may be affected by case sensitivity:
> 
>     1. back-refs
>     2. string slices (sequences)
>     3. single character,
>     4. character families (Unicode Properties ...), and
>     5. character class ranges
> 
> **Note**: Single characters and families may appear independently or within a character class.
> 
> For case-insensitive (loose) matching, the implementation already applies Character.toUpperCase() and Character.toLowerCase() to **both the pattern and the input string** for back-refs, slices, and single characters. This effectively makes these constructs closed under case folding.
> 
> This has been verified in the newly added test case **_test/jdk/java/util/regex/CaseFoldingTest.java_**.
> 
> For example:
> 
> Pattern.compile("(?ui)\u017f").matcher("S").matches().      => true
> Pattern.compile("(?ui)[\u017f]").matcher("S").matches()    => true
> 
> The character properties (families)  are not "closed" and should remain unchanged. This is acceptable per RL1.5, if the  behavior is clearly specified (TBD: update javadoc to reflect this).
> 
> **Current Non-Conformance: Character Class Ranges**, as reported in the original bug report.
> 
> Pattern.compile("(?ui)[\u017f-\u017f]").matcher("S").matches()  => false
> vs
> Pattern.compile("(?ui)[S-S]").matcher("\u017f").matches().         => true
> 
> vs Perl. (Perl also claims to support the Unicode's loose match with it it's "i" modifier)
> 
> perl -C -e 'print "S" =~ /[\x{017f}-\x{017f}]/ ? "true\n" : "false\n"'.  => false
> perl -C -e 'print "S" =~ /[\x{017f}-\x{017f}]/**_i_** ? "true\n" : "false\n"'. => **_true_**
> 
> The root issue is that the ran...

Xueming Shen has updated the pull request incrementally with one additional commit since the last revision:

  improve the lookup logic and test case for +00df

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/26285/files
  - new: https://git.openjdk.org/jdk/pull/26285/files/c2afc42c..b85f581f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=26285&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=26285&range=03-04

  Stats: 44 lines in 3 files changed: 31 ins; 3 del; 10 mod
  Patch: https://git.openjdk.org/jdk/pull/26285.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26285/head:pull/26285

PR: https://git.openjdk.org/jdk/pull/26285