Cheaper test for isInteresting in cycle checking

[Cherry-picked 1354d0d]

Author: odersky

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

@@ -129,7 +129,7 @@ object Symbols extends SymUtils {
     final def lastKnownDenotation: SymDenotation =
       lastDenot
 
-    private[core] def defRunId: RunId =
+    private[dotc] def defRunId: RunId =
       lastDenot.validFor.runId
 
     private inline def associatedFileMatches(inline filter: AbstractFile => Boolean)(using Context): Boolean =

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

@@ -322,8 +322,10 @@ object Checking {
               !sym.is(Private) && prefix.derivesFrom(sym.owner)
               || {
                 val pcls = prefix.symbol.moduleClass
-                if pcls.isStaticOwner then pcls.isDefinedInCurrentRun
-                else isInteresting(prefix.prefix)
+                if pcls.isStaticOwner then
+                  pcls.span.exists && pcls.defRunId == ctx.runId // cheaper approximation to isDefinedInCurrentRun
+                else
+                  isInteresting(prefix.prefix)
               }
             case SuperType(thistp, _) => isInteresting(thistp)
             case AndType(tp1, tp2) => isInteresting(tp1) || isInteresting(tp2)