Merge pull request #9468 from dotty-staging/trait-ctors-reduce-error-output

print flags if -Ydebug

Author: nicolasstucki

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

@@ -477,7 +477,8 @@ object Checking {
     if (sym.isValueClass && sym.is(Trait) && !sym.isRefinementClass)
       fail(CannotExtendAnyVal(sym))
     if (sym.isConstructor && !sym.isPrimaryConstructor && sym.owner.is(Trait, butNot = JavaDefined))
-      fail("Traits cannot have secondary constructors " + sym.owner.flagsString)
+      val addendum = if ctx.settings.Ydebug.value then s" ${sym.owner.flagsString}" else ""
+      fail("Traits cannot have secondary constructors" + addendum)
     checkCombination(Final, Open)
     checkCombination(Sealed, Open)
     checkCombination(Final, Sealed)