如何识别 Scala 宏中的匿名类? [英] How to recognize an anonymous class in a Scala macro?

问题描述

我有一个枚举类成员的宏.我想扩展宏，以便它通过在表单中​​将内部枚举到任何类成员中来递归地工作:

I have a macro which enumerates class members. I would like to extend the macro so that it works recursively by enumerating inside into any class members in a form:

    object obj {
      var name = "value"
      var nested = new {
        var x = 0
      }
    }

在过渡到宏之前我使用的运行时反射中，对我来说效果很好的相应测试是symbol.info.widen =:= typeOf[AnyRef]，但是这不能用于宏，因为在这个 can 中类型不是 AnyRef，而是它的子类(细化).

In a runtime reflection I have used before transitioning to macros the corresponding test which works well for me is symbol.info.widen =:= typeOf[AnyRef], however this cannot work with macro, as in this can the type is not AnyRef, but its subclass (refinement).

当我将类型打印到控制台时，我得到例如:

When I print the type to the console, I get e.g.:

AnyRef{def x: Int;def x_=(x$1: Int): 单位}

当我列出所有基类时，我得到:

When I list all base classes, I get:

List(, class Object, class Any)

我不能使用测试 <:，因为几乎任何东西都会通过这样的测试.

I cannot use a test <:< typeOf[AnyRef], as almost anything would pass such test.

我该如何测试?

这是函数的反射版本，工作正常:

Here is the reflection version of the function, working fine:

  def listMembersNested_A(m: Any): Seq[(String, Any)] = {
    import scala.reflect.runtime.currentMirror
    import scala.reflect.runtime.universe._

    val anyMirror = currentMirror.reflect(m)
    val members = currentMirror.classSymbol(m.getClass).toType.members
    val items = for {
      symbol <- members
      if symbol.isTerm && !symbol.isMethod && !symbol.isModule
    } yield {
      val field = anyMirror.reflectField(symbol.asTerm)
      symbol.name.decodedName.toString.trim -> (if (symbol.info.widen =:= typeOf[AnyRef]) {
        listMembersNested_A(field.get)
      } else {
        field.get
      })
    }
    items.toSeq
  }

它的宏对应物(它是一个物化宏):

Its macro counterpart (it is a materialization macro):

    def impl[O: c.WeakTypeTag](c: blackbox.Context): c.Expr[ListMembersNested[O]] = {
      import c.universe._

      val O = weakTypeOf[O]

      val dive = O.members.sorted.collect {
        case f if f.isMethod && f.asMethod.paramLists.isEmpty && f.asMethod.isGetter =>
          val fName = f.name.decodedName.toString
          if (f.info.widen =:= typeOf[AnyRef]) { /// <<<<<< this does not work
            q"$fName -> listMembersNested(t.$f)"
          } else {
            q"$fName -> t.$f"
          }
      }
      val r = q" Seq(..$dive)"
      val membersExpr = c.Expr[Seq[(String, Any)]](r)

      reify {
        new ListMembersNested[O] {
          def listMembers(t: O) = membersExpr.splice
        }
      }
    }

推荐答案

在你的宏中尝试用类型匹配的模式替换 if-else

In your macro try to replace if-else with pattern matching by types

val anyRefType = typeOf[AnyRef]

f.info match {
  case NullaryMethodType(RefinedType(List(`anyRefType`), _)) =>
    q"$fName -> listMembersNested(t.$f)"
  case _ =>
    q"$fName -> t.$f"
}

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