From d8f1fa55af2d832c07d89abaf9ecffc44c6572f8 Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Thu, 20 Feb 2014 10:43:54 +0100
Subject: Performance tuning: Inline TypeAlias case for hot maps.

---
 src/dotty/tools/dotc/core/Types.scala | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

(limited to 'src/dotty/tools/dotc/core/Types.scala')

diff --git a/src/dotty/tools/dotc/core/Types.scala b/src/dotty/tools/dotc/core/Types.scala
index aab70a61b..9a7fc59b8 100644
--- a/src/dotty/tools/dotc/core/Types.scala
+++ b/src/dotty/tools/dotc/core/Types.scala
@@ -1871,6 +1871,11 @@ object Types {
       if ((lo eq this.lo) && (hi eq this.hi) && (variance == this.variance)) this
       else TypeBounds(lo, hi, variance)
 
+    /** pre: this is a type alias */
+    def derivedTypeAlias(tp: Type, variance: Int = this.variance)(implicit ctx: Context) =
+      if (lo eq tp) this
+      else TypeAlias(tp, variance)
+
     def contains(tp: Type)(implicit ctx: Context) = lo <:< tp && tp <:< hi
 
     def & (that: TypeBounds)(implicit ctx: Context): TypeBounds =
@@ -2124,8 +2129,9 @@ object Types {
         if (lo eq hi) {
           val saved = variance
           variance = variance * tp.variance
-          val lo1 = try this(lo) finally variance = saved
-          tp.derivedTypeBounds(lo1, lo1)
+          val lo1 = this(lo)
+          variance = saved
+          tp.derivedTypeAlias(lo1)
         } else {
           variance = -variance
           val lo1 = this(lo)
@@ -2247,8 +2253,9 @@ object Types {
         if (lo eq hi) {
           val saved = variance
           variance = variance * bounds.variance
-          try this(x, lo)
-          finally variance = saved
+          val result = this(x, lo)
+          variance = saved
+          result
         }
         else {
           variance = -variance
-- 
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