在宏扩展时访问特定符号的 typeSignature 时确认编译失败

Question

我不得不查看宏中的特定声明并单独检查它们。许多此类错误在尝试检查 akka 流声明时发生。

def getType(symbol: Symbol): Type = {
  symbol.typeSignature
}

[error] error while loading SmallSortedMap$Entry, class file '/Users/xxx/.ivy2/cache/com.typesafe.akka/akka-protobuf_2.13/jars/akka-protobuf_2.13-2.5.23.jar(akka/protobuf/SmallSortedMap$Entry.class)' is broken
[error] (class java.util.NoSuchElementException/key not found: K)

这样看来，访问特定符号的typeSygnature时似乎出错了。

我要忽略这个，隐藏它，编译成功

def getType(symbol: Symbol): Option[Type] = {
  Try {
    symbol.typeSignature
  }.getOrElse(None) // Can not capture
}

不过，好像“class坏掉了”用“Try”抓不到。例如，带有此符号的包被排除在黑名单之外。因此，每次添加依赖时都可能发生复杂的维护。

  if (symbol.isNotBroken) {
    symbol.typeSignature
  }

这种方式有办法解决吗？

尝试

我试过 typeCheck。

implicit class RichVectorSymbol(value: Vector[Symbol]) {
    def accessible: Vector[Symbol] = {
      value.flatMap { x =>
        scala.util.Try {
          print(s"typecheck ${x.fullName} ")
          c.typecheck(q"${c.parse(x.fullName)}", silent = true)
        } match {
          case Success(r) if r.nonEmpty =>
            println("Success")
            Some(r.symbol)
          case Failure(e) =>
            println("Fail")
            c.warning(c.enclosingPosition, e.getMessage)
            None
          case _ =>
            println("Empty")
            None
        }
      }
    }
  }

结果。

// Success case
typecheck akka.event.jul.Logger Success
typecheck akka.io.dns.CachePolicy Success
typecheck akka.io.dns.DnsSettings Success

// Fail case
typecheck com.fasterxml.jackson.databind.ObjectMapper [error] error while loading ObjectMapper, class file '/Users/xxxxx/.ivy2/cache/com.fasterxml.jackson.core/jackson-databind/bundles/jackson-databind-2.9.8.jar(com/fasterxml/jackson/databind/ObjectMapper.class)' is broken
[error] (class java.util.NoSuchElementException/key not found: T)
Empty
typecheck akka.protobuf.SmallSortedMap$Entry [error] error while loading SmallSortedMap$Entry, class file '/Users/xxxxx/.ivy2/cache/com.typesafe.akka/akka-protobuf_2.13/jars/akka-protobuf_2.13-2.5.23.jar(akka/protobuf/SmallSortedMap$Entry.class)' is broken
[error] (class java.util.NoSuchElementException/key not found: K)
Empty

像这样，我被逼编译出错了。样本在这里。 https://github.com/giiita/scaladia/blob/master/scaladia-macro/src/main/scala/com/phylage/scaladia/internal/AutoDIExtractor.scala

调试

看了scala源码后，我在内部抛出一个明确的IOException，但我无法捕捉到它，所以我报告了这个问题以防万一 https://github.com/scala/bug/issues/11611

Answer 1

在宏中你可以试试

c.typecheck(q"${... some tree ...}", silent = true)

If tree 不对这个 returns 空树进行类型检查。

akka.protobuf.SmallSortedMap$Entry 中的内容似乎是美元符号。如果我们将 $ 替换为 # 或 . 则错误 class file is broken 变为 class SmallSortedMap in package protobuf cannot be accessed in package akka.protobuf，这是因为 SmallSortedMap has package-private（Java默认）访问。

当我将类型作为字符串参数提供给宏并使用 # 或 . 而不是 $ 时，我设法捕获了错误。

  def foo[T]: Unit = macro fooImpl[T]

  def fooImpl[T: c.WeakTypeTag](c: blackbox.Context): c.Tree = {
    import c.universe._
    try {
      println(weakTypeOf[T].typeSymbol.typeSignature)
    } catch {
      case ex: Throwable => println(ex)
    }
    q"()"
  }

  def foo1(tpe: String): Unit = macro foo1Impl

  def foo1Impl(c: blackbox.Context)(tpe: c.Tree): c.Tree = {
    import c.universe._
    val q"${tpeStr: String}" = tpe
    try {
      println(c.typecheck(c.parse(s"val ${c.freshName()}: $tpeStr = ???")))
//      println(c.typecheck(c.parse(tpeStr), mode = c.TYPEmode))
//      println(c.typecheck(c.parse(tpeStr), mode = c.TYPEmode).symbol.companion.typeSignature)
//      println(c.typecheck(c.parse(tpeStr), mode = c.TYPEmode).tpe.typeSymbol.typeSignature)
//      println(c.typecheck(c.parse(tpeStr), mode = c.TYPEmode).tpe)
    } catch {
      case ex: Throwable => println(ex)
    }
    q"()"
  }

  foo[Int]
//  foo[akka.protobuf.SmallSortedMap$Entry]//Error:scalac: error while loading SmallSortedMap$Entry, class file '.ivy2/cache/com.typesafe.akka/akka-protobuf_2.13/jars/akka-protobuf_2.13-2.5.23.jar(akka/protobuf/SmallSortedMap$Entry.class)' is broken(class java.util.NoSuchElementException/key not found: K)
//  foo[akka.protobuf.SmallSortedMap#Entry]//Error: class SmallSortedMap in package protobuf cannot be accessed in package akka.protobuf
//  foo[akka.protobuf.SmallSortedMap.Entry]//Error:class SmallSortedMap in package protobuf cannot be accessed in package akka.protobuf

//  foo1("Int")
//  foo1("akka.protobuf.SmallSortedMap$Entry")//Error:scalac: error while loading SmallSortedMap$Entry, class file '.ivy2/cache/com.typesafe.akka/akka-protobuf_2.13/jars/akka-protobuf_2.13-2.5.23.jar(akka/protobuf/SmallSortedMap$Entry.class)' is broken (class java.util.NoSuchElementException/key not found: K)
  foo1("akka.protobuf.SmallSortedMap#Entry")//Warning:scalac: scala.reflect.macros.TypecheckException: class SmallSortedMap in package protobuf cannot be accessed in package akka.protobuf
  foo1("akka.protobuf.SmallSortedMap.Entry")//Warning:scalac: scala.reflect.macros.TypecheckException: class SmallSortedMap in package protobuf cannot be accessed in package akka.protobuf

否则，当您调用 foo[... SomeType ...] 时，SomeType 会在宏 foo 展开之前进行类型检查。

http://www.scala-archive.org/Expand-macros-before-typechecking-its-arguments-trees-td4641188.html

在宏扩展时访问特定符号的 typeSignature 时确认编译失败

Compilation failure is confirmed at the moment of accessing typeSignature of a specific symbol at macro expansion

scala

scala-macros

尝试

调试