Fix cyclic reference errors in collection strawman

compiler/src/dotty/tools/dotc/core/TypeApplications.scala

@@ -443,7 +443,7 @@ class TypeApplications(val self: Type) extends AnyVal {
       case dealiased: TypeBounds =>
         dealiased.derivedTypeBounds(dealiased.lo.appliedTo(args), dealiased.hi.appliedTo(args))
       case dealiased: LazyRef =>
-        LazyRef(() => dealiased.ref.appliedTo(args))
+        LazyRef(c => dealiased.ref(c).appliedTo(args))
       case dealiased: WildcardType =>
         WildcardType(dealiased.optBounds.appliedTo(args).bounds)
       case dealiased: TypeRef if dealiased.symbol == defn.NothingClass =>

compiler/src/dotty/tools/dotc/core/Types.scala

@@ -2149,25 +2149,23 @@ object Types {
     }
   }
 
-  case class LazyRef(private var refFn: () => Type) extends UncachedProxyType with ValueType {
+  case class LazyRef(private var refFn: Context => Type) extends UncachedProxyType with ValueType {
     private var myRef: Type = null
     private var computed = false
-    def ref = {
+    def ref(implicit ctx: Context) = {
       if (computed) assert(myRef != null)
       else {
         computed = true
-        myRef = refFn()
+        myRef = refFn(ctx)
+        refFn = null
       }
       myRef
     }
     def evaluating = computed && myRef == null
     override def underlying(implicit ctx: Context) = ref
-    override def toString = s"LazyRef($ref)"
-    override def equals(other: Any) = other match {
-      case other: LazyRef => this.ref.equals(other.ref)
-      case _ => false
-    }
-    override def hashCode = ref.hashCode + 37
+    override def toString = s"LazyRef(...)"
+    override def equals(other: Any) = this eq other.asInstanceOf[AnyRef]
+    override def hashCode = System.identityHashCode(this)
   }
 
   // --- Refined Type and RecType ------------------------------------------------
@@ -3768,7 +3766,7 @@ object Types {
           derivedSuperType(tp, this(thistp), this(supertp))
 
         case tp: LazyRef =>
-          LazyRef(() => this(tp.ref))
+          LazyRef(_ => this(tp.ref))
 
         case tp: ClassInfo =>
           mapClassInfo(tp)

compiler/src/dotty/tools/dotc/core/tasty/TastyFormat.scala

@@ -164,6 +164,7 @@ Standard-Section: "ASTs" TopLevelStat*
                   BIND           Length boundName_NameRef bounds_Type
                                         // for type-variables defined in a type pattern
                   BYNAMEtype            underlying_Type
+                  LAZYref               underlying_Type
                   POLYtype       Length result_Type NamesTypes
                   METHODtype     Length result_Type NamesTypes      // needed for refinements
                   TYPELAMBDAtype Length result_Type NamesTypes      // variance encoded in front of name: +/-/(nothing)
@@ -256,7 +257,7 @@ object TastyFormat {
   final val OBJECTCLASS = 40
 
   final val SIGNED = 63
-  
+
   final val firstInternalTag = 64
   final val IMPLMETH = 64
 
@@ -322,6 +323,7 @@ object TastyFormat {
   final val PROTECTEDqualified = 105
   final val RECtype = 106
   final val SINGLETONtpt = 107
+  final val LAZYref = 108
 
   final val IDENT = 112
   final val IDENTtpt = 113
@@ -512,6 +514,7 @@ object TastyFormat {
     case DOUBLEconst => "DOUBLEconst"
     case STRINGconst => "STRINGconst"
     case RECtype => "RECtype"
+    case LAZYref => "LAZYref"
 
     case IDENT => "IDENT"
     case IDENTtpt => "IDENTtpt"

compiler/src/dotty/tools/dotc/core/tasty/TreePickler.scala

@@ -246,6 +246,7 @@ class TreePickler(pickler: TastyPickler) {
     case tpe: ParamRef =>
       assert(pickleParamRef(tpe), s"orphan parameter reference: $tpe")
     case tpe: LazyRef =>
+      writeByte(LAZYref)
       pickleType(tpe.ref)
   }
 

compiler/src/dotty/tools/dotc/core/tasty/TreeUnpickler.scala

@@ -293,6 +293,10 @@ class TreeUnpickler(reader: TastyReader, nameAtRef: NameRef => TermName, posUnpi
           RecType(rt => registeringType(rt, readType()))
         case RECthis =>
           RecThis(readTypeRef().asInstanceOf[RecType])
+        case LAZYref =>
+          val rdr = fork
+          skipTree()
+          LazyRef(implicit ctx => rdr.readType())
         case SHARED =>
           val ref = readAddr()
           typeAtAddr.getOrElseUpdate(ref, forkAt(ref).readType())
@@ -991,7 +995,12 @@ class TreeUnpickler(reader: TastyReader, nameAtRef: NameRef => TermName, posUnpi
               val refinements = readStats(refineCls, end)(localContext(refineCls))
               RefinedTypeTree(parent, refinements, refineCls)
             case APPLIEDtpt =>
-              AppliedTypeTree(readTpt(), until(end)(readTpt()))
+              // If we do directly a tpd.AppliedType tree we might get a
+              // wrong number of arguments in some scenarios reading F-bounded
+              // types. This came up in #137 of collection strawman.
+              val tycon = readTpt()
+              val args = until(end)(readTpt())
+              untpd.AppliedTypeTree(tycon, args).withType(tycon.tpe.safeAppliedTo(args.tpes))
             case ANDtpt =>
               val tpt1 = readTpt()
               val tpt2 = readTpt()

compiler/src/dotty/tools/dotc/reporting/diagnostic/messages.scala

@@ -23,6 +23,7 @@ import dotty.tools.dotc.ast.Trees
 import dotty.tools.dotc.ast.untpd.Modifiers
 import dotty.tools.dotc.core.Flags.{FlagSet, Mutable}
 import dotty.tools.dotc.core.SymDenotations.SymDenotation
+import scala.util.control.NonFatal
 
 object messages {
 
@@ -708,10 +709,15 @@ object messages {
 
     private val actualArgString = actual.map(_.show).mkString("[", ", ", "]")
 
-    private val prettyName = fntpe.termSymbol match {
-      case NoSymbol => fntpe.show
-      case symbol   => symbol.showFullName
-    }
+    private val prettyName =
+      try
+        fntpe.termSymbol match {
+          case NoSymbol => fntpe.show
+          case symbol   => symbol.showFullName
+        }
+      catch {
+        case NonFatal(ex) => fntpe.show
+      }
 
     val msg =
       hl"""|${NoColor(msgPrefix)} type arguments for $prettyName$expectedArgString

compiler/src/dotty/tools/dotc/typer/Checking.scala

@@ -249,7 +249,7 @@ object Checking {
         } catch {
           case ex: CyclicReference =>
             ctx.debuglog(i"cycle detected for $tp, $nestedCycleOK, $cycleOK")
-            if (cycleOK) LazyRef(() => tp)
+            if (cycleOK) LazyRef(_ => tp)
             else if (reportErrors) throw ex
             else tp
         }