[RaphaelFakhri]

Parser.descape indexes the 128-entry HexChars table with the raw escape character. A non-ASCII character in a \u escape, such as "\u00é0", throws ArrayIndexOutOfBoundsException. Parser.parse treats that as end of input and throws IncompleteParseException("exhausted input"). As a result:

• Sync parsers fail with "exhausted input" and no position, instead of ParseException: expected valid unicode escape.
• AsyncParser.absorb and finalAbsorb throw instead of returning Left.

This change treats any character outside the table as an invalid hex digit, so these inputs fail the same way "\uqqqq" already does.

Tests

SyntaxCheck adds two properties for non-ASCII escape characters (Latin-1, two-byte and three-byte UTF-8). One checks the String and ByteBuffer parsers and the other checks AsyncParser. Both fail on main and pass with the fix. parserJVM/test and astJVM/test pass on Scala 2.12, 2.13 and 3.

Fixes #800

[eed3si9n]

Thanks!