From 95098ba498b5317002395008376a565550189673 Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Sun, 13 Dec 2015 15:34:38 +0100
Subject: Shortcut in derivesFrom for high bound Any.

Any is a supertype of every other type, so no need to analyze types in detail.
This also fixes the cyclic reference error observed for sets.scala, but only
for the special case where the base class is Any.
---
 src/dotty/tools/dotc/core/Types.scala | 31 +++++++++++++++++--------------
 1 file changed, 17 insertions(+), 14 deletions(-)

(limited to 'src/dotty/tools/dotc/core')

diff --git a/src/dotty/tools/dotc/core/Types.scala b/src/dotty/tools/dotc/core/Types.scala
index f65633595..596d1ba24 100644
--- a/src/dotty/tools/dotc/core/Types.scala
+++ b/src/dotty/tools/dotc/core/Types.scala
@@ -141,20 +141,23 @@ object Types {
     }
 
     /** Is this type an instance of a non-bottom subclass of the given class `cls`? */
-    final def derivesFrom(cls: Symbol)(implicit ctx: Context): Boolean = this match {
-      case tp: TypeRef =>
-        val sym = tp.symbol
-        if (sym.isClass) sym.derivesFrom(cls) else tp.underlying.derivesFrom(cls)
-      case tp: TypeProxy =>
-        tp.underlying.derivesFrom(cls)
-      case tp: AndType =>
-        tp.tp1.derivesFrom(cls) || tp.tp2.derivesFrom(cls)
-      case tp: OrType =>
-        tp.tp1.derivesFrom(cls) && tp.tp2.derivesFrom(cls)
-      case tp: JavaArrayType =>
-        cls == defn.ObjectClass
-      case _ =>
-        false
+    final def derivesFrom(cls: Symbol)(implicit ctx: Context): Boolean = {
+      def loop(tp: Type) = tp match {
+        case tp: TypeRef =>
+          val sym = tp.symbol
+          if (sym.isClass) sym.derivesFrom(cls) else tp.underlying.derivesFrom(cls)
+        case tp: TypeProxy =>
+          tp.underlying.derivesFrom(cls)
+        case tp: AndType =>
+          tp.tp1.derivesFrom(cls) || tp.tp2.derivesFrom(cls)
+        case tp: OrType =>
+          tp.tp1.derivesFrom(cls) && tp.tp2.derivesFrom(cls)
+        case tp: JavaArrayType =>
+          cls == defn.ObjectClass
+        case _ =>
+          false
+      }
+      cls == defn.AnyClass || loop(this)
     }
 
     /** Is this type guaranteed not to have `null` as a value?
-- 
cgit v1.2.3