We would like to switch LoadImplicitClosure and LoadFrameClosure to be simple operands, to reduce the complexity of code surrounding them. Unfortunately, in order to make LoadImplicitClosure into an operand (PassedBlock), Operand#retrieve needs to receive the passed block. That cascades into changes to Instr#interpret and callers of each. At the moment it was deemed "polishing the diamond", too big and too risky for too little gain. I will provide a patch based on the almost-complete version (minus the massive refactoring).