From c476171d838c55bbfe36856e73a470e826748acc Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Mon, 27 Jan 2014 15:35:12 +0100
Subject: Cache result of narrow on Methods.

narrow is exercised a lot after the improvement to normalize. So it's important to cache it in order not to bust `uniques` with NoprefixTermRefs.
---
 src/dotty/tools/dotc/core/Types.scala   | 11 ++++++++++-
 src/dotty/tools/dotc/core/Uniques.scala |  7 ++++++-
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/src/dotty/tools/dotc/core/Types.scala b/src/dotty/tools/dotc/core/Types.scala
index 38ed09ebd..4f740d2e5 100644
--- a/src/dotty/tools/dotc/core/Types.scala
+++ b/src/dotty/tools/dotc/core/Types.scala
@@ -965,6 +965,15 @@ object Types {
     def map(tm: TypeMap): ProtoType
   }
 
+  /** Implementations of this trait cache the resukts of `narrow`. */
+  trait NarrowCached extends Type {
+    private var myNarrow: TermRef = null
+    override def narrow(implicit ctx: Context): TermRef = {
+      if (myNarrow eq null) myNarrow = super.narrow
+      myNarrow
+    }
+  }
+
 // --- NamedTypes ------------------------------------------------------------------
 
   /** A NamedType of the form Prefix # name */
@@ -1408,7 +1417,7 @@ object Types {
 
   abstract case class MethodType(paramNames: List[TermName], paramTypes: List[Type])
       (resultTypeExp: MethodType => Type)
-    extends CachedGroundType with BindingType with TermType with MethodOrPoly { thisMethodType =>
+    extends CachedGroundType with BindingType with TermType with MethodOrPoly with NarrowCached { thisMethodType =>
 
     override val resultType = resultTypeExp(this)
     assert(resultType != NoType)
diff --git a/src/dotty/tools/dotc/core/Uniques.scala b/src/dotty/tools/dotc/core/Uniques.scala
index 765b5d73f..9ad736c9c 100644
--- a/src/dotty/tools/dotc/core/Uniques.scala
+++ b/src/dotty/tools/dotc/core/Uniques.scala
@@ -24,7 +24,12 @@ object Uniques {
   def unique[T <: Type](tp: T)(implicit ctx: Context): T = {
     if (monitored) recordCaching(tp)
     if (tp.hash == NotCached) tp
-    else ctx.uniques.findEntryOrUpdate(tp).asInstanceOf[T]
+    else if (monitored) {
+      val size = ctx.uniques.size
+      val result = ctx.uniques.findEntryOrUpdate(tp).asInstanceOf[T]
+      if (ctx.uniques.size > size) record(s"fresh unique ${tp.getClass}")
+      result
+    } else ctx.uniques.findEntryOrUpdate(tp).asInstanceOf[T]
   } /* !!! DEBUG
   ensuring (
     result => tp.toString == result.toString || {
-- 
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