a = 0
d = [1, nil, " sdfg"]
a = rand.instance_eval do
  def d.abc
  end
end

$ /home/mruby/build/host/bin/mruby input.rb
/home/mruby/src/class.c:927:23: runtime error: member access within null pointer of type 'struct REnv'
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /home/mruby/src/class.c:927:23 in
AddressSanitizer:DEADLYSIGNAL
=================================================================
==54350==ERROR: AddressSanitizer: SEGV on unknown address 0x000000000010 (pc 0x0000004f4734 bp 0x7fffffddcff0 sp 0x7fffffddcfa0 T0)
==54350==The signal is caused by a READ memory access.
==54350==Hint: address points to the zero page.
    #0 0x4f4734 in find_visibility_scope /home/mruby/src/class.c:927:26
    #1 0x4f3b66 in mrb_define_method_raw /home/mruby/src/class.c:1003:5
    #2 0x5f2970 in mrb_vm_exec /home/mruby/src/vm.c:3031:7
    #3 0x6f8164 in mrb_load_exec /home/mruby/mrbgems/mruby-compiler/core/parse.y:6935:7
    #4 0x6f94b9 in mrb_load_detect_file_cxt /home/mruby/mrbgems/mruby-compiler/core/parse.y:6978:12
    #5 0x4c7aed in main /home/mruby/mrbgems/mruby-bin-mruby/tools/mruby/mruby.c:353:11
    #6 0x7f21a13e4082 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x24082)
    #7 0x41d81d in _start (/home/mruby/build/host/bin/mruby+0x41d81d)
AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV /home/mruby/src/class.c:927:26 in find_visibility_scope
==54350==ABORTING