Scala example source code file (ReflectGlobal.scala)

This example Scala source code file (ReflectGlobal.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

classloader, classtag, compiler, global, javamirror, mirror, mirrortag, nsc, reflectglobal, runtimeclass, runtimeclasstag, symbol

The ReflectGlobal.scala Scala example source code

package scala.tools
package reflect

import scala.tools.nsc.Global
import scala.tools.nsc.reporters.Reporter
import scala.tools.nsc.Settings

/** A version of Global that uses reflection to get class
 *  infos, instead of reading class or source files.
 */
class ReflectGlobal(currentSettings: Settings, reporter: Reporter, override val rootClassLoader: ClassLoader)
  extends Global(currentSettings, reporter) with scala.tools.reflect.ReflectSetup with scala.reflect.runtime.SymbolTable {

  override def transformedType(sym: Symbol) =
    postErasure.transformInfo(sym,
      erasure.transformInfo(sym,
        uncurry.transformInfo(sym,
          refChecks.transformInfo(sym, sym.info))))

  override def isCompilerUniverse = true

  // Typically `runtimeMirror` creates a new mirror for every new classloader
  // and shares symbols between the created mirrors.
  //
  // However we can't do that for the compiler.
  // The problem is that symbol sharing violates owner chain assumptions that the compiler has.
  //
  // For example, we can easily end up with a situation when:
  //
  //   Predef defined in package scala loaded by the classloader that has scala-library.jar
  //
  // cannot be accessed in:
  //
  //   package scala for the rootMirror of ReflectGlobal that might correspond to a different classloader
  //
  // This happens because, despite the fact that `Predef` is shared between multiple `scala` packages (i.e. multiple scopes)
  // (each mirror has its own set package symbols, because of the peculiarities of symbol loading in scala),
  // that `Predef` symbol only has a single owner, and this messes up visibility, which is calculated based on owners, not scopes.
  override def runtimeMirror(cl: ClassLoader): Mirror = rootMirror

  // Mirror and RuntimeClass come from both Global and reflect.runtime.SymbolTable
  // so here the compiler needs an extra push to help decide between those (in favor of the latter)
  import scala.reflect.ClassTag
  override type Mirror = JavaMirror
  override implicit val MirrorTag: ClassTag[Mirror] = ClassTag[Mirror](classOf[Mirror])
  override type RuntimeClass = java.lang.Class[_]
  override implicit val RuntimeClassTag: ClassTag[RuntimeClass] = ClassTag[RuntimeClass](classOf[RuntimeClass])
}