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package org.scalamacros.paradise
package reflect

import java.lang.{Class => jClass}
import java.lang.reflect.{ Method, InvocationTargetException, UndeclaredThrowableException }

trait ReflectionUtils {
  self: Enrichments =>
  import global._

  // Unwraps some chained exceptions which arise during reflective calls.
  def unwrapThrowable(x: Throwable): Throwable = x match {
    case  _: InvocationTargetException |      // thrown by reflectively invoked method or constructor
          _: ExceptionInInitializerError |    // thrown when running a static initializer (e.g. a scala module constructor)
          _: UndeclaredThrowableException |   // invocation on a proxy instance if its invocation handler's `invoke` throws an exception
          _: ClassNotFoundException |         // no definition for a class instantiated by name
          _: NoClassDefFoundError             // the definition existed when the executing class was compiled, but can no longer be found
            if x.getCause != null =>
              unwrapThrowable(x.getCause)
    case _ => x
  }

  // Transforms an exception handler into one which will only receive the unwrapped
  // exceptions (for the values of wrap covered in unwrapThrowable.)
  def unwrapHandler[T](pf: PartialFunction[Throwable, T]): PartialFunction[Throwable, T] = {
    case ex if pf isDefinedAt unwrapThrowable(ex)   => pf(unwrapThrowable(ex))
  }
}