docs: private Statement store(final Expression expr, final Optional<Label> firstVarInstruction) {
      expr.checkAssignableTo(resultType());
      return new Statement() {
        @Override
        protected void doGen(CodeBuilder adapter) {
          expr.gen(adapter);
          if (firstVarInstruction.isPresent()) {
            adapter.mark(firstVarInstruction.get());
          }
          adapter.visitVarInsn(resultType().getOpcode(Opcodes.ISTORE), index());
        }
      };
    }