Fix for exponential compile time in specialization.

Review by @Prokopec.

Author: paulp

src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala

@@ -1366,7 +1366,7 @@ abstract class SpecializeTypes extends InfoTransform with TypingTransformers {
 
     override def transform(tree: Tree): Tree =
       reportError { transform1(tree) } {_ => tree}
-    
+
     def transform1(tree: Tree) = {
       val symbol = tree.symbol
 
@@ -1437,7 +1437,10 @@ abstract class SpecializeTypes extends InfoTransform with TypingTransformers {
                 localTyper.typedOperator(atPos(tree.pos)(tree1)) // being polymorphic, it must be a method
               }
 
-            case None => super.transform(tree)
+            case None =>
+              treeCopy.TypeApply(tree, treeCopy.Select(sel, qual1, name), super.transformTrees(targs))
+              // See pos/exponential-spec.scala - can't call transform on the whole tree again.
+              // super.transform(tree)
           }
 
         case Select(Super(_, _), name) if illegalSpecializedInheritance(currentClass) =>

test/files/pos/exponential-spec.scala

@@ -0,0 +1,47 @@
+// a.scala
+// Sat Jun 30 19:51:17 PDT 2012
+
+trait Exp[T]
+
+object Test {
+  def f[T](exp: Exp[T]): Exp[T] = (
+    f[T] _ 
+      compose f[T]
+      compose f[T]
+      compose f[T]
+      compose f[T]
+      compose f[T]
+      compose f[T]
+      compose f[T]
+      compose f[T]
+      compose f[T]
+      compose f[T]      // 4s
+      compose f[T]      // 5s
+      compose f[T]      // 5s
+      compose f[T]      // 6s
+      compose f[T]      // 7s
+      compose f[T]      // 8s
+      compose f[T]      // 11s
+      compose f[T]      // 17s
+      compose f[T]      // 29s
+      compose f[T]      // 54s
+      compose f[T]
+      compose f[T]
+      compose f[T]
+      compose f[T]
+      compose f[T]
+      compose f[T]
+      compose f[T]
+      compose f[T]
+      compose f[T]
+      compose f[T]
+      compose f[T]
+      compose f[T]
+      compose f[T]
+      compose f[T]
+      compose f[T]
+      compose f[T]
+      compose f[T]
+      compose f[T]      
+    )(exp)
+}