Issue #20504 has been updated by Eregon (Benoit Daloze). Agreed, the current behavior breaks referential transparency and unexpectedly analyzes string literals inside interpolated parts. This leads to extra confusion and I would think has no value in real-world usages of interpolated regexps (because it causes an error instead of none). So I think this is a bug and the implementation should not analyze those parts and consequently the behavior should be the same as with the extra local variable. ---------------------------------------- Misc #20504: Interpolated string literal in regexp encoding handling https://bugs.ruby-lang.org/issues/20504#change-108433 * Author: kddnewton (Kevin Newton) * Status: Open ---------------------------------------- There is some very odd behavior that I'm not sure is intentional or not, so I'm looking for guidance. In here: ```ruby # encoding: us-ascii interp = "\x80" regexp = /#{interp}/ ``` the `regexp` variable is a ascii-8bit regular expression with the byte interpolated into the middle. However, if you inline that interpolation: ```ruby # encoding: us-ascii regexp = /#{"\x80"}/ ``` you get a syntax error, saying it's an invalid multi-byte character. I'm not sure what the rule is here, as it seems inconsistent. Is this the correct behavior? I would prefer if it would create an ascii-8bit regular expression like the first example, which would be consistent. -- https://bugs.ruby-lang.org/