First compiler run id is now InitialRunId instead of InitialRunId + 1

This is an attempt at fixing stale symbol errors

Author: allanrenucci

compiler/src/dotty/tools/dotc/Compiler.scala

@@ -122,9 +122,11 @@ class Compiler {
     List(new GenBCode) ::            // Generate JVM bytecode
     Nil
 
-  var runId: Int = 1
-  def nextRunId: Int = {
-    runId += 1; runId
+  private[this] var runId: Int = Periods.InitialRunId
+  def nextRunId(): Int = {
+    val next = runId
+    runId += 1
+    next
   }
 
   def reset()(implicit ctx: Context): Unit = {

compiler/src/dotty/tools/dotc/Run.scala

@@ -44,7 +44,7 @@ class Run(comp: Compiler, ictx: Context) extends ImplicitRunInfo with Constraint
     ctx.base.setPhasePlan(comp.phases)
     val rootScope = new MutableScope
     val bootstrap = ctx.fresh
-      .setPeriod(Period(comp.nextRunId, FirstPhaseId))
+      .setPeriod(Period(comp.nextRunId(), FirstPhaseId))
       .setScope(rootScope)
     rootScope.enter(ctx.definitions.RootPackage)(bootstrap)
     val start = bootstrap.fresh