From 058729ceac3354a2cc34490b528e76afb09ee0ce Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Fri, 8 Aug 2014 16:12:01 +0200
Subject: LazyRefs break cycles for unpickled types

Insert LazyRefs to break cycles for F-bounded types that
are unpickled or read from Java signatures.
---
 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 a81d200d3..8ec5c7295 100644
--- a/src/dotty/tools/dotc/core/Types.scala
+++ b/src/dotty/tools/dotc/core/Types.scala
@@ -1236,7 +1236,7 @@ object Types {
       if (ctx.underlyingRecursions < LogPendingUnderlyingThreshold)
         op
       else if (ctx.pendingUnderlying contains this)
-        throw new CyclicReference(symbol)
+        throw CyclicReference(symbol)
       else
         try {
           ctx.pendingUnderlying += this
@@ -1487,7 +1487,7 @@ object Types {
       unique(new CachedConstantType(value))
   }
 
-  case class LazyRef(refFn: () => Type) extends UncachedProxyType with TermType {
+  case class LazyRef(refFn: () => Type) extends UncachedProxyType with ValueType {
     lazy val ref = refFn()
     override def underlying(implicit ctx: Context) = ref
     override def toString = s"LazyRef($ref)"
@@ -2689,10 +2689,17 @@ object Types {
     extends FatalTypeError(
       s"""malformed type: $pre is not a legal prefix for $denot because it contains abstract type member${if (absMembers.size == 1) "" else "s"} ${absMembers.mkString(", ")}""")
 
-  class CyclicReference(val denot: SymDenotation)
+  class CyclicReference private (val denot: SymDenotation)
     extends FatalTypeError(s"cyclic reference involving $denot") {
     def show(implicit ctx: Context) = s"cyclic reference involving ${denot.show}"
-    printStackTrace()
+  }
+
+  object CyclicReference {
+    def apply(denot: SymDenotation)(implicit ctx: Context): CyclicReference = {
+      val ex = new CyclicReference(denot)
+      if (!(ctx.mode is typer.Mode.CheckCyclic)) ex.printStackTrace()
+      ex
+    }
   }
 
   class MergeError(msg: String) extends FatalTypeError(msg)
-- 
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