Made typedUnApply a hook that has to be overridden in a ReTyper.

Change exhibits a problem in the transformers: pattern matching try's
do not seem to be handled.

Author: odersky

src/dotty/tools/dotc/typer/Applications.scala

@@ -763,15 +763,11 @@ trait Applications extends Compatibility { self: Typer =>
     }
   }
 
-  /** A dummmy typed unapply, to make re-typers between frontend and pattern matcher
-   *  visit all subnodes of an unApply tree.
+  /** A typed unapply hook, can be overridden by re any-typers between frontend
+   *  and pattern matcher.
    */
-  def typedUnApply(tree: untpd.UnApply, selType: Type)(implicit ctx: Context) = {
-    val unappType = typed(tree.fun)
-    tree.implicits.foreach(typed(_))
-    tree.patterns.foreach(typedPattern(_))
-    tree.withType(selType)
-  }
+  def typedUnApply(tree: untpd.UnApply, selType: Type)(implicit ctx: Context) =
+    throw new UnsupportedOperationException("cannot type check an UnApply node")
 
   /** Is given method reference applicable to type arguments `targs` and argument trees `args`?
    *  @param  resultType   The expected result type of the application