RedundantStringChars gives invalid code advice

[forthrin]

Expected behavior

Use [0, 2] instead of .chars[0, 2].join if anything.

Actual behavior

a.rb:1:7: C: [Correctable] Performance/RedundantStringChars: Use [0] instead of chars[0, 2].
'foo'.chars[0, 2].join
      ^^^^^^^^^^^

Following the advice as given will produce invalid code.

(Issue was found while trying different techniques to make printf indent correctly for multibyte chars.)

Steps to reproduce the problem

'foo'.chars[0, 2].join

RuboCop version

ruby      2025-08-01 30a20bc16
rubocop   2025-10-04 a08091813
System Version: macOS 15.6 (24G84)
Model Identifier: MacBookAir10,1