问题
I had to look at specific declarations in the macro and examine them individually. Many such errors occurred when trying to examine the akka stream declaration.
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)
In this way, it seems that an error occurs when accessing a typeSygnature for a specific symbol.
I want to ignore this, hide it and compile successfully
def getType(symbol: Symbol): Option[Type] = {
Try {
symbol.typeSignature
}.getOrElse(None) // Can not capture
}
However, it seems that "class is broken" can not be caught by "Try". For example, packages with this symbol are excluded as blacklists. As a result, complex maintenance may occur each time a dependency is added.
if (symbol.isNotBroken) {
symbol.typeSignature
}
Is there a way to solve this way?
Try
I tried 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
}
}
}
}
as a result.
// 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$2 [error] error while loading ObjectMapper$2, class file '/Users/xxxxx/.ivy2/cache/com.fasterxml.jackson.core/jackson-databind/bundles/jackson-databind-2.9.8.jar(com/fasterxml/jackson/databind/ObjectMapper$2.class)' is broken
[error] (class java.util.NoSuchElementException/key not found: T)
Empty
typecheck akka.protobuf.SmallSortedMap$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
Like this, I've been forced to compile error. The sample is here. https://github.com/giiita/scaladia/blob/master/scaladia-macro/src/main/scala/com/phylage/scaladia/internal/AutoDIExtractor.scala
Debugging
After reading the scala source code, I was throwing a clear IOException internally, but I could not catch it, so I reported the issue just in case https://github.com/scala/bug/issues/11611
回答1:
In macro you can try
c.typecheck(q"${... some tree ...}", silent = true)
If tree doesn't typecheck this returns empty tree.
The thing seems to be in dollar sign in akka.protobuf.SmallSortedMap$Entry. If we replace $ with # or . then error class file is broken changes to class SmallSortedMap in package protobuf cannot be accessed in package akka.protobuf, this is because SmallSortedMap has package-private (Java default) access.
I managed to catch the error when I feed type as a string parameter to macro and use # or . instead of $.
def foo[T]: Unit = macro fooImpl[T]
def fooImpl[T: c.WeakTypeTag](c: blackbox.Context): c.Tree = {
import c.universe._
try {
println(weakTypeOf[T].typeSymbol.typeSignature)
} catch {
case ex: Throwable => println(ex)
}
q"()"
}
def foo1(tpe: String): Unit = macro foo1Impl
def foo1Impl(c: blackbox.Context)(tpe: c.Tree): c.Tree = {
import c.universe._
val q"${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
Otherwise when you call foo[... SomeType ...], SomeType is typechecked before macro foo is expanded.
https://stackoverflow.com/a/56754290/5249621
http://www.scala-archive.org/Expand-macros-before-typechecking-its-arguments-trees-td4641188.html
来源：https://stackoverflow.com/questions/56890996/compilation-failure-is-confirmed-at-the-moment-of-accessing-typesignature-of-a-s