Adds debug logging for synthetic registration.

Investigatory tools for SI-5877

Author: retronym

src/compiler/scala/tools/nsc/CompilationUnits.scala

@@ -23,7 +23,7 @@ trait CompilationUnits { self: Global =>
   /** One unit of compilation that has been submitted to the compiler.
     * It typically corresponds to a single file of source code.  It includes
     * error-reporting hooks.  */
-  class CompilationUnit(val source: SourceFile) extends CompilationUnitContextApi {
+  class CompilationUnit(val source: SourceFile) extends CompilationUnitContextApi { self =>
 
     /** the fresh name creator */
     var fresh: FreshNameCreator = new FreshNameCreator.Default
@@ -57,7 +57,23 @@ trait CompilationUnits { self: Global =>
 
     /** Synthetic definitions generated by namer, eliminated by typer.
      */
-    val synthetics = mutable.HashMap[Symbol, Tree]()
+    object synthetics {
+      private val map = mutable.HashMap[Symbol, Tree]()
+      def update(sym: Symbol, tree: Tree) {
+        debuglog(s"adding synthetic ($sym, $tree) to $self")
+        map.update(sym, tree)
+      }
+      def -=(sym: Symbol) {
+        debuglog(s"removing synthetic $sym from $self")
+        map -= sym
+      }
+      def get(sym: Symbol): Option[Tree] = logResultIf[Option[Tree]](s"found synthetic for $sym in $self", _.isDefined) {
+        map get sym
+      }
+      def keys: Iterable[Symbol] = map.keys
+      def clear(): Unit = map.clear()
+      override def toString = map.toString
+    }
 
     /** things to check at end of compilation unit */
     val toCheck = new ListBuffer[() => Unit]