Harden IDE

In interactive mode, allow uncompleted symbols with completers from
previous runs. This is possible due to the way we bring forwward stale
symbols. Liek in manual cleanup in InteractiveDriver, we set the info
of such symbols to UnspecifiedError.

Author: odersky

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

@@ -761,7 +761,7 @@ object Denotations {
     def invalidateInheritedInfo(): Unit = ()
 
     private def updateValidity()(implicit ctx: Context): this.type = {
-      assert(ctx.runId > validFor.runId || ctx.settings.YtestPickler.value, // mixing test pickler with debug printing can travel back in time
+      assert(ctx.runId >= validFor.runId || ctx.settings.YtestPickler.value, // mixing test pickler with debug printing can travel back in time
           s"denotation $this invalid in run ${ctx.runId}. ValidFor: $validFor")
       var d: SingleDenotation = this
       do {

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

@@ -754,8 +754,11 @@ class Namer { typer: Typer =>
           else levels(c.outer) + 1
         println(s"!!!completing ${denot.symbol.showLocated} in buried typerState, gap = ${levels(ctx)}")
       }
-      assert(ctx.runId == creationContext.runId, s"completing $denot in wrong run ${ctx.runId}, was created in ${creationContext.runId}")
-      completeInCreationContext(denot)
+      if (ctx.runId > creationContext.runId) {
+        assert(ctx.mode.is(Mode.Interactive), s"completing $denot in wrong run ${ctx.runId}, was created in ${creationContext.runId}")
+        denot.info = UnspecifiedErrorType
+      }
+      else completeInCreationContext(denot)
     }
 
     private def addInlineInfo(denot: SymDenotation) = original match {