diff --git a/compiler/src/dotty/tools/dotc/ast/Desugar.scala b/compiler/src/dotty/tools/dotc/ast/Desugar.scala
index fd09af8a9ee5..bbde5522484b 100644
--- a/compiler/src/dotty/tools/dotc/ast/Desugar.scala
+++ b/compiler/src/dotty/tools/dotc/ast/Desugar.scala
@@ -766,7 +766,7 @@ object desugar {
     }
 
     flatTree(cdef1 :: companions ::: implicitWrappers)
-  }.reporting(res => i"desugared: $res", Printers.desugar)
+  }.reporting(i"desugared: $result", Printers.desugar)
 
   /** Expand
    *
diff --git a/compiler/src/dotty/tools/dotc/core/Decorators.scala b/compiler/src/dotty/tools/dotc/core/Decorators.scala
index 37a6e3e10c4f..0ca6b7f86c98 100644
--- a/compiler/src/dotty/tools/dotc/core/Decorators.scala
+++ b/compiler/src/dotty/tools/dotc/core/Decorators.scala
@@ -1,4 +1,5 @@
-package dotty.tools.dotc
+package dotty.tools
+package dotc
 package core
 
 import annotation.tailrec
@@ -168,11 +169,16 @@ object Decorators {
       }
   }
 
-  implicit class genericDeco[T](val x: T) extends AnyVal {
-    def reporting(op: T => String, printer: config.Printers.Printer = config.Printers.default): T = {
-      printer.println(op(x))
+  implicit object reportDeco {
+    def (x: T) reporting[T](
+        op: given WrappedResult[T] => String,
+        printer: config.Printers.Printer = config.Printers.default): T = {
+      printer.println(op given WrappedResult(x))
       x
     }
+  }
+
+  implicit class genericDeco[T](val x: T) extends AnyVal {
     def assertingErrorsReported(implicit ctx: Context): T = {
       assert(ctx.reporter.errorsReported)
       x
diff --git a/compiler/src/dotty/tools/dotc/core/Denotations.scala b/compiler/src/dotty/tools/dotc/core/Denotations.scala
index 331d593a2644..e15a4ba59025 100644
--- a/compiler/src/dotty/tools/dotc/core/Denotations.scala
+++ b/compiler/src/dotty/tools/dotc/core/Denotations.scala
@@ -757,8 +757,8 @@ object Denotations {
 
     def atSignature(sig: Signature, site: Type, relaxed: Boolean)(implicit ctx: Context): SingleDenotation = {
       val situated = if (site == NoPrefix) this else asSeenFrom(site)
-      val matches = sig.matchDegree(situated.signature) >=
-        (if (relaxed) Signature.ParamMatch else Signature.FullMatch)
+      val matches = sig.matchDegree(situated.signature).ordinal >=
+        (if (relaxed) Signature.ParamMatch else Signature.FullMatch).ordinal
       if (matches) this else NoDenotation
     }
 
@@ -1096,7 +1096,7 @@ object Denotations {
        d == Signature.FullMatch &&
        !infoOrCompleter.isInstanceOf[PolyType] && !other.infoOrCompleter.isInstanceOf[PolyType]
        ||
-       d >= Signature.ParamMatch && info.matches(other.info))
+       d != Signature.NoMatch && info.matches(other.info))
     }
 
     def mapInherited(ownDenots: PreDenotation, prevDenots: PreDenotation, pre: Type)(implicit ctx: Context): SingleDenotation =
diff --git a/compiler/src/dotty/tools/dotc/core/Flags.scala b/compiler/src/dotty/tools/dotc/core/Flags.scala
index 464807e98a35..3de27b232634 100644
--- a/compiler/src/dotty/tools/dotc/core/Flags.scala
+++ b/compiler/src/dotty/tools/dotc/core/Flags.scala
@@ -20,11 +20,7 @@ object Flags {
     opaque type Flag <: FlagSet = Long
     private[Flags] def Flag(bits: Long): Flag = bits
   }
-  type FlagSet = opaques.FlagSet
-  def FlagSet(bits: Long): FlagSet = opaques.FlagSet(bits)
-  // DOTTY TODO: replace previous 2 lines with
-  //   export opaques.FlagSet
-  // once 0.17 is released and #6721 is in the bootstrap
+  export opaques.FlagSet
 
   type Flag = opaques.Flag
 
diff --git a/compiler/src/dotty/tools/dotc/core/GadtConstraint.scala b/compiler/src/dotty/tools/dotc/core/GadtConstraint.scala
index 11b869b8f995..e31821e2b5e0 100644
--- a/compiler/src/dotty/tools/dotc/core/GadtConstraint.scala
+++ b/compiler/src/dotty/tools/dotc/core/GadtConstraint.scala
@@ -123,9 +123,8 @@ final class ProperGadtConstraint private(
     }
 
     // The replaced symbols are picked up here.
-    addToConstraint(poly1, tvars).reporting({ _ =>
-      i"added to constraint: $params%, %\n$debugBoundsDescription"
-    }, gadts)
+    addToConstraint(poly1, tvars)
+      .reporting(i"added to constraint: $params%, %\n$debugBoundsDescription", gadts)
   }
 
   override def addBound(sym: Symbol, bound: Type, isUpper: Boolean)(implicit ctx: Context): Boolean = {
@@ -159,7 +158,7 @@ final class ProperGadtConstraint private(
           val oldUpperBound = bounds(symTvar.origin)
           // If we have bounds:
           //     F >: [t] => List[t] <: [t] => Any
-          // and we want to record that: 
+          // and we want to record that:
           //     F <: [+A] => List[A]
           // we need to adapt the variance and instead record that:
           //     F <: [A] => List[A]
@@ -177,10 +176,10 @@ final class ProperGadtConstraint private(
           if (isUpper) addUpperBound(symTvar.origin, bound1)
           else addLowerBound(symTvar.origin, bound1)
       }
-    ).reporting({ res =>
+    ).reporting({
       val descr = if (isUpper) "upper" else "lower"
       val op = if (isUpper) "<:" else ">:"
-      i"adding $descr bound $sym $op $bound = $res"
+      i"adding $descr bound $sym $op $bound = $result"
     }, gadts)
   }
 
@@ -206,7 +205,7 @@ final class ProperGadtConstraint private(
             case tb => tb
           }
         retrieveBounds
-          //.reporting({ res => i"gadt bounds $sym: $res" }, gadts)
+          //.reporting(i"gadt bounds $sym: $result", gadts)
           //.ensuring(containsNoInternalTypes(_))
     }
   }
diff --git a/compiler/src/dotty/tools/dotc/core/OrderingConstraint.scala b/compiler/src/dotty/tools/dotc/core/OrderingConstraint.scala
index 740882a1cc63..76d5ac88d38c 100644
--- a/compiler/src/dotty/tools/dotc/core/OrderingConstraint.scala
+++ b/compiler/src/dotty/tools/dotc/core/OrderingConstraint.scala
@@ -548,7 +548,7 @@ class OrderingConstraint(private val boundsMap: ParamBounds,
         merge(this.boundsMap, that.boundsMap, mergeEntries),
         merge(this.lowerMap, that.lowerMap, mergeParams),
         merge(this.upperMap, that.upperMap, mergeParams))
-  }.reporting(res => i"constraint merge $this with $other = $res", constr)
+  }.reporting(i"constraint merge $this with $other = $result", constr)
 
   def rename(tl: TypeLambda)(implicit ctx: Context): OrderingConstraint = {
     assert(contains(tl))
diff --git a/compiler/src/dotty/tools/dotc/core/Signature.scala b/compiler/src/dotty/tools/dotc/core/Signature.scala
index 4999c9eb90be..977bcef3f252 100644
--- a/compiler/src/dotty/tools/dotc/core/Signature.scala
+++ b/compiler/src/dotty/tools/dotc/core/Signature.scala
@@ -107,10 +107,10 @@ case class Signature(paramsSig: List[TypeName], resSig: TypeName) {
 
 object Signature {
 
-  type MatchDegree = Int
-  val NoMatch: Int = 0
-  val ParamMatch: Int = 1
-  val FullMatch: Int = 2
+  enum MatchDegree {
+    case NoMatch, ParamMatch, FullMatch
+  }
+  export MatchDegree._
 
   /** The signature of everything that's not a method, i.e. that has
    *  a type different from PolyType, MethodType, or ExprType.
diff --git a/compiler/src/dotty/tools/dotc/core/SymDenotations.scala b/compiler/src/dotty/tools/dotc/core/SymDenotations.scala
index 67ee4bd91d0f..df91418e7979 100644
--- a/compiler/src/dotty/tools/dotc/core/SymDenotations.scala
+++ b/compiler/src/dotty/tools/dotc/core/SymDenotations.scala
@@ -187,46 +187,34 @@ object SymDenotations {
       if (isCurrent(fs)) myFlags else flags
 
     /** Has this denotation one of given flag set? */
-    final def is(flag: Flag)(implicit ctx: Context): Boolean = {
-      val toTest = if (isCurrent(flag)) myFlags else flags // TODO: combine these two lines once 0.17 is released and #6706 is in
-      toTest.is(flag)
-    }
+    final def is(flag: Flag)(implicit ctx: Context): Boolean =
+      (if (isCurrent(flag)) myFlags else flags).is(flag)
 
     /** Has this denotation one of the flags in `fs` set? */
-    final def isOneOf(fs: FlagSet)(implicit ctx: Context): Boolean = {
-      val toTest = if (isCurrent(fs)) myFlags else flags // TODO: combine these two lines once 0.17 is released and #6706 is in
-      toTest.isOneOf(fs)
-    }
+    final def isOneOf(fs: FlagSet)(implicit ctx: Context): Boolean =
+      (if (isCurrent(fs)) myFlags else flags).isOneOf(fs)
 
     /** Has this denotation the given flag set, whereas none of the flags
      *  in `butNot` are set?
      */
-    final def is(flag: Flag, butNot: FlagSet)(implicit ctx: Context): Boolean = {
-      val toTest = if (isCurrent(flag) && isCurrent(butNot)) myFlags else flags // TODO: combine these two lines once 0.17 is released and #6706 is in
-      toTest.is(flag, butNot)
-    }
+    final def is(flag: Flag, butNot: FlagSet)(implicit ctx: Context): Boolean =
+      (if (isCurrent(flag) && isCurrent(butNot)) myFlags else flags).is(flag, butNot)
 
     /** Has this denotation one of the flags in `fs` set, whereas none of the flags
      *  in `butNot` are set?
      */
-    final def isOneOf(fs: FlagSet, butNot: FlagSet)(implicit ctx: Context): Boolean = {
-      val toTest = if (isCurrent(fs) && isCurrent(butNot)) myFlags else flags // TODO: combine these two lines once 0.17 is released and #6706 is in
-      toTest.isOneOf(fs, butNot)
-    }
+    final def isOneOf(fs: FlagSet, butNot: FlagSet)(implicit ctx: Context): Boolean =
+      (if (isCurrent(fs) && isCurrent(butNot)) myFlags else flags).isOneOf(fs, butNot)
 
     /** Has this denotation all of the flags in `fs` set? */
-    final def isAllOf(fs: FlagSet)(implicit ctx: Context): Boolean = {
-      val toTest = if (isCurrent(fs)) myFlags else flags // TODO: combine these two lines once 0.17 is released and #6706 is in
-      toTest.isAllOf(fs)
-    }
+    final def isAllOf(fs: FlagSet)(implicit ctx: Context): Boolean =
+      (if (isCurrent(fs)) myFlags else flags).isAllOf(fs)
 
     /** Has this denotation all of the flags in `fs` set, whereas none of the flags
      *  in `butNot` are set?
      */
-    final def isAllOf(fs: FlagSet, butNot: FlagSet)(implicit ctx: Context): Boolean = {
-      val toTest = if (isCurrent(fs) && isCurrent(butNot)) myFlags else flags // TODO: combine these two lines once 0.17 is released and #6706 is in
-      toTest.isAllOf(fs, butNot)
-    }
+    final def isAllOf(fs: FlagSet, butNot: FlagSet)(implicit ctx: Context): Boolean =
+      (if (isCurrent(fs) && isCurrent(butNot)) myFlags else flags).isAllOf(fs, butNot)
 
     /** The type info, or, if symbol is not yet completed, the completer */
     final def infoOrCompleter: Type = myInfo
diff --git a/compiler/src/dotty/tools/dotc/core/Symbols.scala b/compiler/src/dotty/tools/dotc/core/Symbols.scala
index 496eacbdf546..11e57c3f9233 100644
--- a/compiler/src/dotty/tools/dotc/core/Symbols.scala
+++ b/compiler/src/dotty/tools/dotc/core/Symbols.scala
@@ -782,7 +782,7 @@ object Symbols {
               }
             sourceFromTopLevel(ctx.withPhaseNoLater(ctx.flattenPhase))
           }
-        }//.reporting(res => i"source of $this # $id in ${denot.owner} = $res")
+        }//.reporting(i"source of $this # $id in ${denot.owner} = $result")
       mySource
     }
 
diff --git a/compiler/src/dotty/tools/dotc/reporting/MessageRendering.scala b/compiler/src/dotty/tools/dotc/reporting/MessageRendering.scala
index ce15d818260b..1b28cbc8996a 100644
--- a/compiler/src/dotty/tools/dotc/reporting/MessageRendering.scala
+++ b/compiler/src/dotty/tools/dotc/reporting/MessageRendering.scala
@@ -119,7 +119,7 @@ trait MessageRendering {
         else s"${pos.source.file.toString}: offset ${pos.start} (missing source file)"
       val errId =
         if (message.errorId ne ErrorMessageID.NoExplanationID) {
-          val errorNumber = message.errorId.errorNumber()
+          val errorNumber = message.errorId.errorNumber
           s"[E${"0" * (3 - errorNumber.toString.length) + errorNumber}] "
         } else ""
       val kind =
diff --git a/compiler/src/dotty/tools/dotc/reporting/diagnostic/ErrorMessageID.java b/compiler/src/dotty/tools/dotc/reporting/diagnostic/ErrorMessageID.scala
similarity index 95%
rename from compiler/src/dotty/tools/dotc/reporting/diagnostic/ErrorMessageID.java
rename to compiler/src/dotty/tools/dotc/reporting/diagnostic/ErrorMessageID.scala
index b84b2cf17af7..bbfe6c1e505a 100644
--- a/compiler/src/dotty/tools/dotc/reporting/diagnostic/ErrorMessageID.java
+++ b/compiler/src/dotty/tools/dotc/reporting/diagnostic/ErrorMessageID.scala
@@ -1,10 +1,10 @@
-package dotty.tools.dotc.reporting.diagnostic;
+package dotty.tools.dotc.reporting.diagnostic
 
 /** Unique IDs identifying the messages */
-public enum ErrorMessageID {
-
-    // IMPORTANT: Add new IDs only at the end and never remove IDs
+enum ErrorMessageID extends java.lang.Enum[ErrorMessageID] {
 
+  // IMPORTANT: Add new IDs only at the end and never remove IDs
+  case
     LazyErrorId, // // errorNumber: -2
     NoExplanationID, // errorNumber: -1
 
@@ -146,10 +146,6 @@ public enum ErrorMessageID {
     StableIdentPatternID,
     StaticFieldsShouldPrecedeNonStaticID,
     IllegalSuperAccessorID
-    ;
-
-    public int errorNumber() {
-        return ordinal() - 2;
-    }
 
+  def errorNumber = ordinal - 2
 }
diff --git a/compiler/src/dotty/tools/dotc/reporting/diagnostic/messages.scala b/compiler/src/dotty/tools/dotc/reporting/diagnostic/messages.scala
index 675365864c98..1d37ba7c8edf 100644
--- a/compiler/src/dotty/tools/dotc/reporting/diagnostic/messages.scala
+++ b/compiler/src/dotty/tools/dotc/reporting/diagnostic/messages.scala
@@ -2154,11 +2154,13 @@ object messages {
       val details = if (decl.isRealMethod && previousDecl.isRealMethod) {
         // compare the signatures when both symbols represent methods
         decl.signature.matchDegree(previousDecl.signature) match {
-          case Signature.NoMatch =>
+          case Signature.MatchDegree.NoMatch =>
+            // DOTTY problem: Need to qualify MatchDegree enum vals since otherwise exhaustivity fails.
+            // To fix this, we need to export vals under singleton types.
             "" // shouldn't be reachable
-          case Signature.ParamMatch =>
+          case Signature.MatchDegree.ParamMatch =>
             "have matching parameter types."
-          case Signature.FullMatch =>
+          case Signature.MatchDegree.FullMatch =>
             i"have the same$nameAnd type after erasure."
         }
       } else ""
diff --git a/compiler/src/dotty/tools/dotc/tastyreflect/KernelImpl.scala b/compiler/src/dotty/tools/dotc/tastyreflect/KernelImpl.scala
index 0e2dddf69555..3d2d674f5730 100644
--- a/compiler/src/dotty/tools/dotc/tastyreflect/KernelImpl.scala
+++ b/compiler/src/dotty/tools/dotc/tastyreflect/KernelImpl.scala
@@ -17,8 +17,6 @@ import dotty.tools.dotc.util.SourceFile
 
 import scala.tasty.reflect.Kernel
 
-import delegate Flags.FlagOps // DOTTY problem: this line can be dropped in 0.17 once #6712 is in bootstrap.
-
 class KernelImpl(val rootContext: core.Contexts.Context, val rootPosition: util.SourcePosition) extends Kernel {
 
   private implicit def ctx: core.Contexts.Context = rootContext
diff --git a/compiler/src/dotty/tools/dotc/transform/CheckReentrant.scala b/compiler/src/dotty/tools/dotc/transform/CheckReentrant.scala
index a573618d90d1..98a3cb12d54e 100644
--- a/compiler/src/dotty/tools/dotc/transform/CheckReentrant.scala
+++ b/compiler/src/dotty/tools/dotc/transform/CheckReentrant.scala
@@ -43,7 +43,10 @@ class CheckReentrant extends MiniPhase {
 
   def isIgnored(sym: Symbol)(implicit ctx: Context): Boolean =
     sym.hasAnnotation(sharableAnnot()) ||
-    sym.hasAnnotation(unsharedAnnot())
+    sym.hasAnnotation(unsharedAnnot()) ||
+    sym.owner == defn.EnumValuesClass
+      // enum values are initialized eagerly before use
+      // in the long run, we should make them vals
 
   def scanning(sym: Symbol)(op: => Unit)(implicit ctx: Context): Unit = {
     ctx.log(i"${"  " * indent}scanning $sym")
diff --git a/compiler/src/dotty/tools/dotc/typer/Inliner.scala b/compiler/src/dotty/tools/dotc/typer/Inliner.scala
index 4595720091b2..76b669d9c655 100644
--- a/compiler/src/dotty/tools/dotc/typer/Inliner.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Inliner.scala
@@ -628,7 +628,7 @@ class Inliner(call: tpd.Tree, rhsToInline: tpd.Tree)(implicit ctx: Context) {
           if (idx >= 0 && idx < args.length) {
             def finish(arg: Tree) =
               new TreeTypeMap().transform(arg) // make sure local bindings in argument have fresh symbols
-                .reporting(res => i"projecting $tree -> $res", inlining)
+                .reporting(i"projecting $tree -> $result", inlining)
             val arg = args(idx)
             if (precomputed)
               if (isPureExpr(arg)) finish(arg)
diff --git a/compiler/src/dotty/tools/dotc/typer/ProtoTypes.scala b/compiler/src/dotty/tools/dotc/typer/ProtoTypes.scala
index f96a0c761503..9eafce747966 100644
--- a/compiler/src/dotty/tools/dotc/typer/ProtoTypes.scala
+++ b/compiler/src/dotty/tools/dotc/typer/ProtoTypes.scala
@@ -401,7 +401,7 @@ object ProtoTypes {
         resType match {
           case SelectionProto(name: TermName, mbrType, _, _) =>
             ctx.typer.hasExtensionMethod(tp, name, argType, mbrType)
-              //.reporting(res => i"has ext $tp $name $argType $mbrType: $res")
+              //.reporting(i"has ext $tp $name $argType $mbrType: $result")
           case _ =>
             false
         }
diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala
index 3621d093c897..24f605eb6310 100644
--- a/compiler/src/dotty/tools/dotc/typer/Typer.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Typer.scala
@@ -2565,7 +2565,7 @@ class Typer extends Namer
               typed(untpd.Select(untpd.New(untpd.TypedSplice(tpt)), nme.CONSTRUCTOR), pt)
           }
           recur(tycon, pt)
-            .reporting(res => i"try new $tree -> $res", typr)
+            .reporting(i"try new $tree -> $result", typr)
         }
       } { (nu, nuState) =>
         if (nu.isEmpty) fallBack
diff --git a/compiler/src/dotty/tools/dotc/typer/Variances.scala b/compiler/src/dotty/tools/dotc/typer/Variances.scala
index 05570bac0bbe..014c23c961ee 100644
--- a/compiler/src/dotty/tools/dotc/typer/Variances.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Variances.scala
@@ -3,7 +3,6 @@ package typer
 
 import core._
 import Types._, Contexts._, Flags._, Symbols._, Annotations._
-import delegate Flags.FlagOps // DOTTY problem: this line can be dropped in 0.17 once #6712 is in bootstrap.
 
 object Variances {
 
diff --git a/compiler/src/dotty/tools/package.scala b/compiler/src/dotty/tools/package.scala
index 2a7506da8d52..416504d40aa4 100644
--- a/compiler/src/dotty/tools/package.scala
+++ b/compiler/src/dotty/tools/package.scala
@@ -23,4 +23,13 @@ package object tools {
   /** Throws an `UnsupportedOperationException` with the given method name. */
   def unsupported(methodName: String): Nothing =
     throw new UnsupportedOperationException(methodName)
+
+  object resultWrapper {
+    opaque type WrappedResult[T] = T
+    private[tools] def unwrap[T](x: WrappedResult[T]): T = x
+    private[tools] def wrap[T](x: T): WrappedResult[T] = x
+  }
+  type WrappedResult[T] = resultWrapper.WrappedResult[T]
+  def WrappedResult[T](x: T) = resultWrapper.wrap(x)
+  def result[T] given (x: WrappedResult[T]): T = resultWrapper.unwrap(x)
 }