code: LocalItem makeTemp(Type type) {
          VarSymbol v = new VarSymbol(Flags.SYNTHETIC,
                                      names.empty,
                                      type,
                                      env.enclMethod.sym);
          code.newLocal(v);
          return items.makeLocalItem(v);
      }
docs: Create a tempory variable.
  @param type   The variable's type.