LazyRefs break cycles for unpickled types

Insert LazyRefs to break cycles for F-bounded types that
are unpickled or read from Java signatures.

2 files changed, 12 insertions, 2 deletions

diff --git a/src/dotty/tools/dotc/core/pickling/ClassfileParser.scala b/src/dotty/tools/dotc/core/pickling/ClassfileParser.scala
index 59658c9c1..193c872f1 100644
--- a/src/dotty/tools/dotc/core/pickling/ClassfileParser.scala
+++ b/src/dotty/tools/dotc/core/pickling/ClassfileParser.scala
@@ -11,6 +11,7 @@ import java.lang.Integer.toHexString
 import scala.collection.{ mutable, immutable }
 import scala.collection.mutable.{ ListBuffer, ArrayBuffer }
 import scala.annotation.switch
+import typer.Checking.checkNonCyclic
 import io.AbstractFile
 
 class ClassfileParser(
@@ -337,7 +338,11 @@ class ClassfileParser(
         val savedIndex = index
         try {
           index = start
-          denot.info = sig2typeBounds(tparams, skiptvs = false)
+          denot.info =
+            checkNonCyclic( // we need the checkNonCyclic call to insert LazyRefs for F-bounded cycles
+                denot.symbol,
+                sig2typeBounds(tparams, skiptvs = false),
+                reportErrors = false)
         } finally {
           index = savedIndex
         }
diff --git a/src/dotty/tools/dotc/core/pickling/UnPickler.scala b/src/dotty/tools/dotc/core/pickling/UnPickler.scala
index de3f626da..2e21358e4 100644
--- a/src/dotty/tools/dotc/core/pickling/UnPickler.scala
+++ b/src/dotty/tools/dotc/core/pickling/UnPickler.scala
@@ -15,6 +15,7 @@ import printing.Texts._
 import printing.Printer
 import io.AbstractFile
 import util.common._
+import typer.Checking.checkNonCyclic
 import PickleBuffer._
 import scala.reflect.internal.pickling.PickleFormat._
 import Decorators._
@@ -516,7 +517,11 @@ class UnPickler(bytes: Array[Byte], classRoot: ClassDenotation, moduleClassRoot:
             denot setFlag Scala2x
           case denot =>
             val tp1 = depoly(tp, denot)
-            denot.info = if (tag == ALIASsym) TypeAlias(tp1) else tp1
+            denot.info =
+              if (tag == ALIASsym) TypeAlias(tp1)
+              else if (denot.isType) checkNonCyclic(denot.symbol, tp1, reportErrors = false)
+                // we need the checkNonCyclic call to insert LazyRefs for F-bounded cycles
+              else tp1
             if (denot.isConstructor) addConstructorTypeParams(denot)
             if (atEnd) {
               assert(!(denot is SuperAccessor), denot)