Top level break instruction causes panic on REPL

[hachi8833]

The following Goby code from https://github.com/goby-lang/goby/blob/master/vm/statement_test.go#L13 causes panic only on REPL:

x = [1, 2, 3]
y = 0
x.each do |i|
  y += i
  if i == 2
    break
  end
end
y

» y
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x68 pc=0x43ef404]

goroutine 1 [running]:
github.com/goby-lang/goby/vm.(*VM).REPLExec(0xc4200a6780, 0xc4201e69c0, 0x5, 0x8)
	/Users/hachi8833/deve/golang/gopath/sys/src/github.com/goby-lang/goby/vm/repl.go:38 +0x4d4
github.com/goby-lang/goby/igb.StartIgb(0x4577c2d, 0x5)
	/Users/hachi8833/deve/golang/gopath/sys/src/github.com/goby-lang/goby/igb/repl.go:231 +0xd23
main.main()
	/Users/hachi8833/deve/golang/gopath/sys/src/github.com/goby-lang/goby/goby.go:29 +0x954

Note that the code works fine when running as a file.

And the following works fine on REPL; looks like the bug only occurs on top level break instruction.

» def foo
¤   x = [1, 2, 3]
¤   y = 0
¤   x.each do |i|
¤     y += i
¤     if i == 2
¤       break
¤     end
¤   end
¤   y
» end
#»
» foo
#» 3

FYI: complied with Go 1.9.3.

[ear7h]

Was looking into this today. Seem like something with the break statement. The following snippet is interesting because it doesn't panic at the break statement, but at an instruction afterwards. I'm guessing that break pops the stack more times than necessary at the top level.

Goby 0.1.7 🙃 😚 😺
» [1, 2, 3].each do |i|
¤   break
» end
#» [1, 2, 3]
»
» y = 0
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x60 pc=0x44006b5]

goroutine 1 [running]:
github.com/goby-lang/goby/vm.(*VM).REPLExec(0xc4200a6820, 0xc4201fa6c0, 0x3, 0x4)
	/Users/julio/lib/go/src/github.com/goby-lang/goby/vm/repl.go:38 +0x435
github.com/goby-lang/goby/igb.StartIgb(0x459e471, 0x5)
	/Users/julio/lib/go/src/github.com/goby-lang/goby/igb/repl.go:231 +0xc13
main.main()
	/Users/julio/lib/go/src/github.com/goby-lang/goby/goby.go:29 +0x8fc

[ear7h]

@hachi8833

Ran another test (see snippet below) and the problem seems to be related to the top level but not with the break statement being on the top level. I'm not really sure why, but some instruction on the top level after the a break statement.

Goby 0.1.7 🤓 😐 🤧
» def foo
¤   [1, 2, 3].each do |i|
¤     break
¤   end
¤   y = 0
» end
#»
» foo
#» 0
» y = 0
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x60 pc=0x44006b5]

goroutine 1 [running]:
github.com/goby-lang/goby/vm.(*VM).REPLExec(0xc4200a68c0, 0xc420204cc0, 0x5, 0x8)
	/Users/julio/lib/go/src/github.com/goby-lang/goby/vm/repl.go:38 +0x435
github.com/goby-lang/goby/igb.StartIgb(0x459e471, 0x5)
	/Users/julio/lib/go/src/github.com/goby-lang/goby/igb/repl.go:231 +0xc13
main.main()
	/Users/julio/lib/go/src/github.com/goby-lang/goby/goby.go:29 +0x8fc