Avoid taking references before toplevel symbols are entered.

Taking a reference means that the symbol will be brought forward into the current run,
then if the same symbol is entered from source, a datarace ensues.

This affected the ProductN symbols because these are automatically added to a case class
suring desugaring.

6 files changed, 30 insertions, 32 deletions

diff --git a/src/dotty/tools/dotc/ast/Desugar.scala b/src/dotty/tools/dotc/ast/Desugar.scala
index 36c99a12b..6c914c934 100644
--- a/src/dotty/tools/dotc/ast/Desugar.scala
+++ b/src/dotty/tools/dotc/ast/Desugar.scala
@@ -323,7 +323,7 @@ object desugar {
 
     def anyRef = ref(defn.AnyRefAlias.typeRef)
     def productConstr(n: Int) = {
-      val tycon = ref(defn.ProductNType(n))
+      val tycon = scalaDot((tpnme.Product.toString + n).toTypeName)
       val targs = constrVparamss.head map (_.tpt)
       if (targs.isEmpty) tycon else AppliedTypeTree(tycon, targs)
     }
diff --git a/src/dotty/tools/dotc/ast/untpd.scala b/src/dotty/tools/dotc/ast/untpd.scala
index 3f3e1bf37..28a3cf1ff 100644
--- a/src/dotty/tools/dotc/ast/untpd.scala
+++ b/src/dotty/tools/dotc/ast/untpd.scala
@@ -201,7 +201,9 @@ object untpd extends Trees.Instance[Untyped] with UntypedTreeInfo {
   def ref(tp: NamedType)(implicit ctx: Context): Tree =
     TypedSplice(tpd.ref(tp))
 
-  def scalaUnit(implicit ctx: Context) = ref(defn.UnitType)
+  def rootDot(name: Name) = Select(Ident(nme.ROOTPKG), name)
+  def scalaDot(name: Name) = Select(rootDot(nme.scala_), name)
+  def scalaUnit = scalaDot(tpnme.Unit)
 
   def makeConstructor(tparams: List[TypeDef], vparamss: List[List[ValDef]], rhs: Tree = EmptyTree)(implicit ctx: Context): DefDef =
     DefDef(nme.CONSTRUCTOR, tparams, vparamss, TypeTree(), rhs)
diff --git a/src/dotty/tools/dotc/core/Types.scala b/src/dotty/tools/dotc/core/Types.scala
index 4cae047a9..2c310aea4 100644
--- a/src/dotty/tools/dotc/core/Types.scala
+++ b/src/dotty/tools/dotc/core/Types.scala
@@ -1387,7 +1387,7 @@ object Types {
         (lastSymbol.infoOrCompleter == ErrorType ||
         sym.owner.derivesFrom(lastSymbol.owner) && sym.owner != lastSymbol.owner
       ),
-        s"data race? overwriting symbol of ${this.show} / $this / ${this.getClass} / ${lastSymbol.id} / ${sym.id} / ${sym.owner} / ${lastSymbol.owner} / ${ctx.phase}")
+        s"data race? overwriting symbol of ${this.show} / $this / ${this.getClass} / ${lastSymbol.id} / ${sym.id} / ${sym.owner} / ${lastSymbol.owner} / ${ctx.phase} at run ${ctx.runId}")
 
     protected def sig: Signature = Signature.NotAMethod
 
diff --git a/src/dotty/tools/dotc/parsing/JavaParsers.scala b/src/dotty/tools/dotc/parsing/JavaParsers.scala
index 52bcdb965..be7822cdc 100644
--- a/src/dotty/tools/dotc/parsing/JavaParsers.scala
+++ b/src/dotty/tools/dotc/parsing/JavaParsers.scala
@@ -92,12 +92,10 @@ object JavaParsers {
 
     // --------- tree building -----------------------------
 
-    def rootId(name: Name)             = Select(Ident(nme.ROOTPKG), name)
-    def scalaDot(name: Name)           = Select(Ident(nme.scala_), name)
     def scalaAnnotationDot(name: Name) = Select(scalaDot(nme.annotation), name)
 
     def javaDot(name: Name): Tree =
-      Select(rootId(nme.java), name)
+      Select(rootDot(nme.java), name)
 
     def javaLangDot(name: Name): Tree =
       Select(javaDot(nme.lang), name)
diff --git a/src/dotty/tools/dotc/parsing/SymbolicXMLBuilder.scala b/src/dotty/tools/dotc/parsing/SymbolicXMLBuilder.scala
index 46d2a450e..20b655a19 100644
--- a/src/dotty/tools/dotc/parsing/SymbolicXMLBuilder.scala
+++ b/src/dotty/tools/dotc/parsing/SymbolicXMLBuilder.scala
@@ -70,7 +70,7 @@ class SymbolicXMLBuilder(parser: Parser, preserveWS: Boolean)(implicit ctx: Cont
   private def const(x: Any) = Literal(Constant(x))
   private def wild                          = Ident(nme.WILDCARD)
   private def wildStar                      = Ident(tpnme.WILDCARD_STAR)
-  private def _scala(name: Name)            = Select(Select(Ident(nme.ROOTPKG), nme.scala_), name)
+  private def _scala(name: Name)            = scalaDot(name)
   private def _scala_xml(name: Name)        = Select(_scala(_xml), name)
 
   private def _scala_xml_Comment            = _scala_xml(_Comment)
diff --git a/test/dotc/scala-collections.whitelist b/test/dotc/scala-collections.whitelist
index 27b1bc5ae..3a8611a20 100644
--- a/test/dotc/scala-collections.whitelist
+++ b/test/dotc/scala-collections.whitelist
@@ -56,31 +56,29 @@
 ./scala-scala/src/library/scala/PartialFunction.scala
 ./scala-scala/src/library/scala/Predef.scala
 
-# Causes data races #907
-# java.lang.AssertionError: assertion failed: data race? overwriting symbol of Product1 / TypeRef(ThisType(TypeRef(NoPrefix,scala)),Product1) / class dotty.tools.dotc.core.Types$CachedTypeRef / 190 / 4820 / module class scala / module class scala / frontend, took 2.154 sec
-#./scala-scala/src/library/scala/Product.scala
-#./scala-scala/src/library/scala/Product1.scala
-#./scala-scala/src/library/scala/Product10.scala
-#./scala-scala/src/library/scala/Product11.scala
-#./scala-scala/src/library/scala/Product12.scala
-#./scala-scala/src/library/scala/Product13.scala
-#./scala-scala/src/library/scala/Product14.scala
-#./scala-scala/src/library/scala/Product15.scala
-#./scala-scala/src/library/scala/Product16.scala
-#./scala-scala/src/library/scala/Product17.scala
-#./scala-scala/src/library/scala/Product18.scala
-#./scala-scala/src/library/scala/Product19.scala
-#./scala-scala/src/library/scala/Product2.scala
-#./scala-scala/src/library/scala/Product20.scala
-#./scala-scala/src/library/scala/Product21.scala
-#./scala-scala/src/library/scala/Product22.scala
-#./scala-scala/src/library/scala/Product3.scala
-#./scala-scala/src/library/scala/Product4.scala
-#./scala-scala/src/library/scala/Product5.scala
-#./scala-scala/src/library/scala/Product6.scala
-#./scala-scala/src/library/scala/Product7.scala
-#./scala-scala/src/library/scala/Product8.scala
-#./scala-scala/src/library/scala/Product9.scala
+./scala-scala/src/library/scala/Product.scala
+./scala-scala/src/library/scala/Product1.scala
+./scala-scala/src/library/scala/Product10.scala
+./scala-scala/src/library/scala/Product11.scala
+./scala-scala/src/library/scala/Product12.scala
+./scala-scala/src/library/scala/Product13.scala
+./scala-scala/src/library/scala/Product14.scala
+./scala-scala/src/library/scala/Product15.scala
+./scala-scala/src/library/scala/Product16.scala
+./scala-scala/src/library/scala/Product17.scala
+./scala-scala/src/library/scala/Product18.scala
+./scala-scala/src/library/scala/Product19.scala
+./scala-scala/src/library/scala/Product2.scala
+./scala-scala/src/library/scala/Product20.scala
+./scala-scala/src/library/scala/Product21.scala
+./scala-scala/src/library/scala/Product22.scala
+./scala-scala/src/library/scala/Product3.scala
+./scala-scala/src/library/scala/Product4.scala
+./scala-scala/src/library/scala/Product5.scala
+./scala-scala/src/library/scala/Product6.scala
+./scala-scala/src/library/scala/Product7.scala
+./scala-scala/src/library/scala/Product8.scala
+./scala-scala/src/library/scala/Product9.scala
 
 
 ./scala-scala/src/library/scala/Proxy.scala