Issue #13064 has been reported by Jrg W Mittag.

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Bug #13064: Inconsistent behavior with `next` inside `begin`/`end` across different implementations.
https://bugs.ruby-lang.org/issues/13064

* Author: Jrg W Mittag
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: ruby 2.4.0dev (2016-12-22 trunk 57151) [x86_64-darwin16]
* Backport: 2.1: UNKNOWN, 2.2: UNKNOWN, 2.3: UNKNOWN
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[@Kalsan over on StackOverflow observed inconsistent behavior](http://stackoverflow.com/q/41283514/2988) with `next` inside `begin`/`end` across different implementations. In particular, Rubinius, JRuby, and MRuby all behave the same while YARV behaves differently. In addition, running the same code inside IRb behaves differently than running it as a script.

Usually, YARV is the gold standard, and if some behavior differs from YARV, YARV is right and the other implementation is wrong. However, in this case, not only do *all other* implementations disagree with YARV, but in particular, MRuby/Rite, the implementation written and maintained by matz himself disagrees with YARV.

So, what is the correct behavior for this (admittedly) non-sensical code?

Here is the behavior across different versions of YARV and different implementations:

* YARV 2.2.0 (the build shipping with macOS)

        # ruby -v -W -e 'begin; begin puts 1; next end; puts 2 end'
        ruby 2.0.0p648 (2015-12-16 revision 53162) [universal.x86_64-darwin16]
        -e:1: warning: statement not reached
        -e:1: Invalid next
        -e: compile error (SyntaxError)

        # irb -f -d -w -W
        irb(main):001:0> p RUBY_VERSION
        "2.0.0"
        => "2.0.0"
        irb(main):002:0> p RUBY_ENGINE
        "ruby"
        => "ruby"
        irb(main):003:0> 
        irb(main):004:0* begin
        irb(main):005:1*   begin
        irb(main):006:2*     puts 1
        irb(main):007:2>     next
        irb(main):008:2>   end
        irb(main):009:1>   puts 2
        irb(main):010:1> end
        (irb):9: warning: statement not reached
        Exception `SyntaxError' at /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/irb/workspace.rb:86 - (irb):7: Can't escape from eval with next
        Exception `SyntaxError' at /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/irb/workspace.rb:86 - (irb):7: Can't escape from eval with next
        SyntaxError: (irb):7: Can't escape from eval with next
        	from (irb)
        irb(main):011:0> 
        irb(main):012:0* exit

* YARV 2.3.1 (the version JRuby claims to be compatible with at the moment)

        # ruby -v -W -e 'begin; begin puts 1; next end; puts 2 end'
        ruby 2.3.1p112 (2016-04-26 revision 54768) [x86_64-darwin16]
        -e:1: warning: statement not reached
        -e: -e:1: Invalid next (SyntaxError)

        # irb -f -d -w -W
        irb(main):001:0> p RUBY_VERSION
        "2.3.1"
        => "2.3.1"
        irb(main):002:0> p RUBY_ENGINE
        "ruby"
        => "ruby"
        irb(main):003:0> 
        irb(main):004:0* begin
        irb(main):005:1*   begin
        irb(main):006:2*     puts 1
        irb(main):007:2>     next
        irb(main):008:2>   end
        irb(main):009:1>   puts 2
        irb(main):010:1> end
        (irb):9: warning: statement not reached
        Exception `SyntaxError' at /Users/joerg/.rbenv/versions/2.3.1/lib/ruby/2.3.0/irb/workspace.rb:87 - (irb):7: Can't escape from eval with next
        Exception `SyntaxError' at /Users/joerg/.rbenv/versions/2.3.1/lib/ruby/2.3.0/irb/workspace.rb:87 - (irb):7: Can't escape from eval with next
        Exception `SyntaxError' at /Users/joerg/.rbenv/versions/2.3.1/lib/ruby/2.3.0/irb/workspace.rb:87 - (irb):7: Can't escape from eval with next
        SyntaxError: (irb):7: Can't escape from eval with next
        	from (irb)
        irb(main):011:0> 
        irb(main):012:0* exit

* YARV 2.3.3

        # ruby -v -W -e 'begin; begin puts 1; next end; puts 2 end'
        ruby 2.3.3p222 (2016-11-21 revision 56859) [x86_64-darwin16]
        -e:1: warning: statement not reached
        -e: -e:1: Invalid next (SyntaxError)

        # irb -f -d -w -W
        irb(main):001:0> p RUBY_VERSION
        "2.3.3"
        => "2.3.3"
        irb(main):002:0> p RUBY_ENGINE
        "ruby"
        => "ruby"
        irb(main):003:0> 
        irb(main):004:0* begin
        irb(main):005:1*   begin
        irb(main):006:2*     puts 1
        irb(main):007:2>     next
        irb(main):008:2>   end
        irb(main):009:1>   puts 2
        irb(main):010:1> end
        (irb):9: warning: statement not reached
        Exception `SyntaxError' at /Users/joerg/.rbenv/versions/2.3.3/lib/ruby/2.3.0/irb/workspace.rb:87 - (irb):7: Can't escape from eval with next
        Exception `SyntaxError' at /Users/joerg/.rbenv/versions/2.3.3/lib/ruby/2.3.0/irb/workspace.rb:87 - (irb):7: Can't escape from eval with next
        Exception `SyntaxError' at /Users/joerg/.rbenv/versions/2.3.3/lib/ruby/2.3.0/irb/workspace.rb:87 - (irb):7: Can't escape from eval with next
        SyntaxError: (irb):7: Can't escape from eval with next
        	from (irb)
        irb(main):011:0> 
        irb(main):012:0* exit

* YARV 2.4.0-preview3:

        # ruby -v -W -e 'begin; begin puts 1; next end; puts 2 end'
        ruby 2.4.0preview3 (2016-11-07 trunk 56661) [x86_64-darwin16]
        -e:1: warning: statement not reached
        -e: -e:1: Invalid next (SyntaxError)

        # irb -f -d -w -W
        irb(main):001:0> p RUBY_VERSION
        "2.4.0"
        => "2.4.0"
        irb(main):002:0> p RUBY_ENGINE
        "ruby"
        => "ruby"
        irb(main):003:0> 
        irb(main):004:0* begin
        irb(main):005:1*   begin
        irb(main):006:2*     puts 1
        irb(main):007:2>     next
        irb(main):008:2>   end
        irb(main):009:1>   puts 2
        irb(main):010:1> end
        (irb):9: warning: statement not reached
        Exception `SyntaxError' at /Users/joerg/.rbenv/versions/2.4.0-preview3/lib/ruby/2.4.0/irb/workspace.rb:87 - (irb):7: Can't escape from eval with next
        SyntaxError: (irb):7: Can't escape from eval with next
        	from (irb)
        irb(main):011:0> 
        irb(main):012:0* exit

* YARV 2.4.0-dev (current SVN trunk as of yesterday):

        # ruby -v -W -e 'begin; begin puts 1; next end; puts 2 end'
        ruby 2.4.0dev (2016-12-22 trunk 57151) [x86_64-darwin16]
        -e:1: warning: statement not reached
        -e: -e:1: Invalid next (SyntaxError)

        # irb -f -d -w -W
        irb(main):001:0> p RUBY_VERSION
        "2.4.0"
        => "2.4.0"
        irb(main):002:0> p RUBY_ENGINE
        "ruby"
        => "ruby"
        irb(main):003:0> 
        irb(main):004:0* begin
        irb(main):005:1*   begin
        irb(main):006:2*     puts 1
        irb(main):007:2>     next
        irb(main):008:2>   end
        irb(main):009:1>   puts 2
        irb(main):010:1> end
        (irb):9: warning: statement not reached
        Exception `SyntaxError' at /Users/joerg/.rbenv/versions/2.4.0-dev/lib/ruby/2.4.0/irb/workspace.rb:87 - (irb):7: Can't escape from eval with next
        SyntaxError: (irb):7: Can't escape from eval with next
        	from (irb)
        irb(main):011:0> 
        irb(main):012:0* exit

* Rubinius 3.69

        # rbx -v -W -e 'begin; begin puts 1; next end; puts 2 end'
        rubinius 3.69 (2.3.1 a57071c6 2016-11-17 3.8.1) [x86_64-darwin15.6.0]
        1
                        main # Rubinius::Loader at core/loader.rb:860
                       evals # Rubinius::Loader at core/loader.rb:646
                        eval # Kernel(Rubinius::Loader) at core/kernel.rb:1130
            call_on_instance # Rubinius::BlockEnvironment at core/block_environment.rb:147
           { } in __script__ # Object at -e:1
                  jump_error . Rubinius at core/rubinius.rb:279

        invalid context for 'next' (LocalJumpError)

        An exception occurred evaluating command line code

        # irb
        irb(main):001:0> p RUBY_VERSION
        "2.3.1"
        => "2.3.1"
        irb(main):002:0> p RUBY_ENGINE
        "rbx"
        => "rbx"
        irb(main):003:0> 
        irb(main):004:0* begin
        irb(main):005:1*   begin
        irb(main):006:2*     puts 1
        irb(main):007:2>     next
        irb(main):008:2>   end
        irb(main):009:1>   puts 2
        irb(main):010:1> end
        1
        LocalJumpError: invalid context for 'next'
        	from core/rubinius.rb:279:in `jump_error'
        	from (irb):7
        	from core/block_environment.rb:147:in `call_on_instance'
        	from core/kernel.rb:1130:in `eval'
        	from core/kernel.rb:585:in `loop'
        	from core/proc.rb:20:in `call'
        	from core/kernel.rb:1067:in `catch'
        	from core/throw_catch.rb:8:in `register'
        	from core/kernel.rb:1066:in `catch'
        	from core/proc.rb:20:in `call'
        	from core/kernel.rb:1067:in `catch'
        	from core/throw_catch.rb:8:in `register'
        	from core/kernel.rb:1066:in `catch'
        	from core/code_loader.rb:505:in `load_script'
        	from core/code_loader.rb:590:in `load_script'
        	from core/loader.rb:679:in `script'
        	from core/loader.rb:861:in `main'irb(main):011:0> 
        irb(main):012:0* exit

* JRuby 9.1.6.0 (the latest release)

        # jruby -v -W -e 'begin; begin puts 1; next end; puts 2 end'
        jruby 9.1.6.0 (2.3.1) 2016-11-09 0150a76 Java HotSpot(TM) 64-Bit Server VM 25.102-b14 on 1.8.0_102-b14 +jit [darwin-x86_64]
        1
        LocalJumpError: unexpected next
          <main> at -e:1

        # irb -f -d -w -W
        irb(main):001:0> p RUBY_VERSION
        "2.3.1"
        => "2.3.1"
        irb(main):002:0> p RUBY_ENGINE
        "jruby"
        => "jruby"
        irb(main):003:0> 
        irb(main):004:0* begin
        irb(main):005:1*   begin
        irb(main):006:2*     puts 1
        irb(main):007:2>     next
        irb(main):008:2>   end
        irb(main):009:1>   puts 2
        irb(main):010:1> end
        1
        => nil
        irb(main):011:0> 
        irb(main):012:0* exit

* MRuby 1.2.0 (the minimal ISO compliant Ruby implementation written by matz himself)

        # mruby -v -e 'begin; begin puts 1; next end; puts 2 end'
        mruby 1.2.0 (2015-11-17) 
        00001 NODE_SCOPE:
        00001   NODE_BEGIN:
        00001     NODE_BEGIN:
        00001       NODE_BEGIN:
        00001         NODE_CALL:
        00001           NODE_SELF
        00001           method='puts' (383)
        00001           args:
        00001             NODE_INT 1 base 10
        00001         NODE_NEXT:
        00001       NODE_CALL:
        00001         NODE_SELF
        00001         method='puts' (383)
        00001         args:
        00001           NODE_INT 2 base 10
        irep 0x7fe0e3c1b630 nregs=4 nlocals=1 pools=1 syms=1 reps=0
        file: -e
            1 000 OP_LOADSELF	R1		
            1 001 OP_LOADI	R2	1	
            1 002 OP_SEND	R1	:puts	1
            1 003 OP_ERR	"unexpected next"
            1 004 OP_LOADSELF	R1		
            1 005 OP_LOADI	R2	2	
            1 006 OP_SEND	R1	:puts	1
            1 007 OP_STOP

        1
        trace:
        	[0] -e:1
        LocalJumpError: unexpected next

        # irb -v
        mruby 1.2.0 (2015-11-17) 
        mirb - Embeddable Interactive Ruby Shell

        > p RUBY_VERSION
        00001 NODE_SCOPE:
        00001   NODE_BEGIN:
        00001     NODE_CALL:
        00001       NODE_SELF
        00001       method='p' (384)
        00001       args:
        00001         NODE_CONST RUBY_VERSION
        irep 0x7fceeac05220 nregs=4 nlocals=1 pools=0 syms=2 reps=0
        file: (mirb)
            1 000 OP_LOADSELF	R1		
            1 001 OP_GETCONST	R2	:RUBY_VERSION
            1 002 OP_SEND	R1	:p	1
            1 003 OP_STOP

        "1.9"
         => "1.9"
        > p RUBY_ENGINE
        00002 NODE_SCOPE:
        00002   NODE_BEGIN:
        00002     NODE_CALL:
        00002       NODE_SELF
        00002       method='p' (384)
        00002       args:
        00002         NODE_CONST RUBY_ENGINE
        irep 0x7fceeae05cf0 nregs=4 nlocals=1 pools=0 syms=2 reps=0
        file: (mirb)
            2 000 OP_LOADSELF	R1		
            2 001 OP_GETCONST	R2	:RUBY_ENGINE
            2 002 OP_SEND	R1	:p	1
            2 003 OP_STOP

        "mruby"
         => "mruby"
        > 
        00004 NODE_SCOPE:
        00004   NODE_BEGIN:
        irep 0x7fceeac06a50 nregs=2 nlocals=1 pools=0 syms=0 reps=0
        file: (mirb)
            4 000 OP_LOADNIL	R1		
            4 001 OP_STOP

         => nil
        > begin
        00005 NODE_NIL
        *   begin
        00007 NODE_NIL
        *     puts 1
        00009 NODE_NIL
        *     next
        00011 NODE_NIL
        *   end
        00013 NODE_NIL
        *   puts 2
        00015 NODE_NIL
        * end
        00012 NODE_SCOPE:
        00012   NODE_BEGIN:
        00012     NODE_BEGIN:
        00012       NODE_BEGIN:
        00012         NODE_CALL:
        00012           NODE_SELF
        00012           method='puts' (383)
        00012           args:
        00012             NODE_INT 1 base 10
        00013         NODE_NEXT:
        00015       NODE_CALL:
        00015         NODE_SELF
        00015         method='puts' (383)
        00015         args:
        00015           NODE_INT 2 base 10
        irep 0x7fceeae01130 nregs=4 nlocals=1 pools=1 syms=1 reps=0
        file: (mirb)
           12 000 OP_LOADSELF	R1		
           12 001 OP_LOADI	R2	1	
           12 002 OP_SEND	R1	:puts	1
           13 003 OP_ERR	"unexpected next"
           15 004 OP_LOADSELF	R1		
           15 005 OP_LOADI	R2	2	
           15 006 OP_SEND	R1	:puts	1
           15 007 OP_STOP

        1
        LocalJumpError: unexpected next
        > 
        00012 NODE_SCOPE:
        00012   NODE_BEGIN:
        irep 0x7fceeae078f0 nregs=2 nlocals=1 pools=0 syms=0 reps=0
        file: (mirb)
           12 000 OP_LOADNIL	R1		
           12 001 OP_STOP

         => nil
        > exit

What is most interesting is that MRuby, JRuby and Rubinius actually agree on the behavior, but differ from YARV. Either YARV or all the other ones are wrong. I cannot say which ones, though.



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