void_fun is rewritten with new visitor

Signed-off-by: Akira Hayakawa <ruby.wktk@gmail.com>
refactor

Signed-off-by: Akira Hayakawa <ruby.wktk@gmail.com>
Add CommaOp

Signed-off-by: Akira Hayakawa <ruby.wktk@gmail.com>
add failure test

Signed-off-by: Akira Hayakawa <ruby.wktk@gmail.com>
Merge branch 'feature/use-comma-op' into develop