Issue #20856 has been updated by Eregon (Benoit Daloze). Backport changed from 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN to 3.1: DONTNEED, 3.2: DONTNEED, 3.3: DONTNEED It's a bug of 3.4.0-preview2 and specifically of the Prism compiler, 3.3 and earlier and `--parser=parse.y` succeed for all cases. The order is: * parse that file: * execute it * in that new thread eval is called * that parses `"a == b"`, with outer scopes [[a,x], [s,b]]. ---------------------------------------- Bug #20856: Incorrect and inconsistent multi-thread eval execution https://bugs.ruby-lang.org/issues/20856#change-110317 * Author: hurricup (Alexandr Evstigneev) * Status: Open * ruby -v: 3.4.0-preview2 * Backport: 3.1: DONTNEED, 3.2: DONTNEED, 3.3: DONTNEED ---------------------------------------- Consider example: ``` s = Thread.new { a = 5 puts eval("a == b") x = 6 } s.join b = 11 ``` As far as I see it, it should not work. Because at the moment of eval, b is unknown and not even declared (it can even be in condition). But it may be available because file `iseq` already compiled and we know that there is b. So, this works in ruby 3.3 in a script we running, wrapped into the method, or required by other file. But in 3.4-preview2: - it works in file - it works in method - it fails if required from other file with: ``` #<Thread:0x00007725530d6a98 /home/hurricup/Projects/ruby-debugger/rdi30/test2.rb:1 run> terminated with exception (report_on_exception is true): (eval at /home/hurricup/Projects/ruby-debugger/rdi30/test2.rb:3):1:in 'block in <top (required)>': undefined local variable or method 'b' for main (NameError) from /home/hurricup/Projects/ruby-debugger/rdi30/test2.rb:3:in 'Kernel#eval' from /home/hurricup/Projects/ruby-debugger/rdi30/test2.rb:3:in 'block in <top (required)>' (eval at /home/hurricup/Projects/ruby-debugger/rdi30/test2.rb:3):1:in 'block in <top (required)>': undefined local variable or method 'b' for main (NameError) from /home/hurricup/Projects/ruby-debugger/rdi30/test2.rb:3:in 'Kernel#eval' from /home/hurricup/Projects/ruby-debugger/rdi30/test2.rb:3:in 'block in <top (required)>' ``` And this ^^ is correct behavior if you ask me :) but atm it is inconsistent between the ruby versions and even in the scope of 3.4-preview2 -- https://bugs.ruby-lang.org/