code: func (v *evalVisitor) popBlock() *ast.BlockStatement {
  	if len(v.blocks) == 0 {
  		return nil
  	}
  
  	var result *ast.BlockStatement
  	result, v.blocks = v.blocks[len(v.blocks)-1], v.blocks[:len(v.blocks)-1]
  
  	return result
  }
docs: // popBlock pops last block statement from stack