Bug #22451: Coderange may be set incorrectly when concatenating a string into itself

• Status: Open
• Assignee: -
• Target version: -
• Backport: 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN

[jhawthorn (John Hawthorn)]

s = "\x81\x30".force_encoding("GB18030")
#=> "\x810"
s.valid_encoding? # This is invalid
#=> false
(s + s).valid_encoding? # However it becomes valid when repeated
#=> true
(s << s).valid_encoding? # But concat assumed the coderange would not change
#=> false
s.b.force_encoding(s.encoding).valid_encoding? # Same bytes, different answer
#=> true

https://github.com/ruby/ruby/pull/19357