diff --git a/build.sbt b/build.sbt
index b022e055c..cd45f4dad 100644
--- a/build.sbt
+++ b/build.sbt
@@ -111,6 +111,30 @@ val boilerplate = Def.taskDyn {
   (Compile / sourceManaged).map(Boilerplate.gen(scalaBinaryVersion.value))
 }
 
+lazy val macroAnnotationSettings = Seq(
+  scalacOptions ++= {
+    CrossVersion.partialVersion(scalaVersion.value) match {
+      case Some((2, v)) if v >= 13 => Seq("-Ymacro-annotations")
+      case _ => Nil
+    }
+  },
+  libraryDependencies ++= {
+    CrossVersion.partialVersion(scalaVersion.value) match {
+      case Some((2, v)) if v <= 12 =>
+        Seq(compilerPlugin("org.scalamacros" % "paradise" % "2.1.1" cross CrossVersion.full))
+      case _ => Nil
+    }
+  },
+)
+
+lazy val coreTestMacros = crossProject(JSPlatform, JVMPlatform, NativePlatform)
+  .crossType(CrossType.Full)
+  .settings(moduleName := "core-test-macros")
+  .settings(commonSettings)
+  .settings(noPublishSettings)
+  .configureCross(buildInfoSetup)
+  .settings(macroAnnotationSettings)
+
 lazy val core = crossProject(JSPlatform, JVMPlatform, NativePlatform)
   .crossType(CrossType.Full)
   .configureCross(configureJUnit)
@@ -123,6 +147,8 @@ lazy val core = crossProject(JSPlatform, JVMPlatform, NativePlatform)
   .settings(Compile / sourceManaged := baseDirectory.value.getParentFile / "shared" / "src" / "main" / "managed")
   .settings(Compile / sourceGenerators += boilerplate.taskValue)
   .settings(mimaSettings)
+  .dependsOn(coreTestMacros % "test->compile")
+  .settings(macroAnnotationSettings)
 
 lazy val coreJVM = core.jvm
 lazy val coreJS = core.js
diff --git a/core/shared/src/main/scala/shapeless/conversions.scala b/core/shared/src/main/scala/shapeless/conversions.scala
index 71f299348..14f4c2e07 100644
--- a/core/shared/src/main/scala/shapeless/conversions.scala
+++ b/core/shared/src/main/scala/shapeless/conversions.scala
@@ -22,12 +22,12 @@ import ops.hlist.Tupler
  * Higher ranked function which converts `HLists` to tuples.
  */
 object tupled extends Poly1 {
-  implicit def caseHList[L <: HList](implicit tupler: Tupler[L]) = at[L](tupler(_))
+  implicit def caseHList[L <: HList](implicit tupler: Tupler[L]): Case.Aux[L, tupler.Out] = at[L](tupler(_))
 }
 
 /**
  * Higher ranked function which converts products to `HLists`. 
  */
 object productElements extends Poly1 {
-  implicit def caseProduct[P](implicit gen: Generic[P]) = at[P](p => gen.to(p))
+  implicit def caseProduct[P](implicit gen: Generic[P]): Case.Aux[P, gen.Repr] = at[P](p => gen.to(p))
 }
diff --git a/core/shared/src/main/scala/shapeless/coproduct.scala b/core/shared/src/main/scala/shapeless/coproduct.scala
index 05b776740..ced87a429 100644
--- a/core/shared/src/main/scala/shapeless/coproduct.scala
+++ b/core/shared/src/main/scala/shapeless/coproduct.scala
@@ -130,7 +130,7 @@ object Coproduct extends Dynamic {
   
   def apply[C <: Coproduct] = new MkCoproduct[C]
 
-  implicit def cpOps[C <: Coproduct](c: C) = new CoproductOps(c) 
+  implicit def cpOps[C <: Coproduct](c: C): CoproductOps[C] = new CoproductOps(c) 
 
   def unsafeMkCoproduct(length: Int, value: Any) =
     (0 until length).foldLeft[Coproduct](Inl(value))((accum, _) => Inr(accum))
diff --git a/core/shared/src/main/scala/shapeless/generic.scala b/core/shared/src/main/scala/shapeless/generic.scala
index cb3432c0e..96806393d 100644
--- a/core/shared/src/main/scala/shapeless/generic.scala
+++ b/core/shared/src/main/scala/shapeless/generic.scala
@@ -1021,9 +1021,12 @@ trait CaseClassMacros extends ReprTypes with CaseClassMacrosVersionSpecifics {
         // case 3: case class
         case tpe if tpe.typeSymbol.asClass.isCaseClass =>
           val companion = patchedCompanionSymbolOf(tpe.typeSymbol)
+          val apply   = companion.typeSignature.member(TermName("apply"))
           val unapply = companion.typeSignature.member(TermName("unapply"))
           val fields = fieldsOf(tpe)
-          (fromApply(fields), if (unapply.isSynthetic) toUnapply(fields) else toGetters(fields))
+          val ctor = if (apply == NoSymbol) fromConstructor(fields) else fromApply(fields)
+          val dtor = if (unapply.isSynthetic) toUnapply(fields) else toGetters(fields)
+          (ctor, dtor)
         // case 4: exactly one matching public apply/unapply
         case HasApplyUnapply(args) =>
           (fromApply(args), toUnapply(args))
diff --git a/core/shared/src/main/scala/shapeless/hmap.scala b/core/shared/src/main/scala/shapeless/hmap.scala
index cdba5c2b3..b4b192930 100644
--- a/core/shared/src/main/scala/shapeless/hmap.scala
+++ b/core/shared/src/main/scala/shapeless/hmap.scala
@@ -36,7 +36,7 @@ class HMap[R[_, _]](underlying : Map[Any, Any] = Map.empty) extends Poly1 {
   def +[K, V](kv : (K, V))(implicit ev : R[K, V]) : HMap[R] = new HMap[R](underlying+kv)
   def -[K](k : K) : HMap[R] = new HMap[R](underlying-k)
 
-  implicit def caseRel[K, V](implicit ev : R[K, V]) = Case1[this.type, K, V](get(_).get)
+  implicit def caseRel[K, V](implicit ev : R[K, V]): Case1.Aux[this.type, K, V] = Case1[this.type, K, V](get(_).get)
 }
 
 object HMap {
diff --git a/core/shared/src/main/scala/shapeless/lenses.scala b/core/shared/src/main/scala/shapeless/lenses.scala
index 531c4a908..524402d01 100644
--- a/core/shared/src/main/scala/shapeless/lenses.scala
+++ b/core/shared/src/main/scala/shapeless/lenses.scala
@@ -159,7 +159,7 @@ object OpticDefns {
   def apply[C] = id[C]
 
   object compose extends Poly2 {
-    implicit def default[A, B, C] = at[Lens[B, C], Lens[A, B]](_ compose _)
+    implicit def default[A, B, C]: Case.Aux[Lens[B, C], Lens[A, B], Lens[A, C]] = at[Lens[B, C], Lens[A, B]](_ compose _)
   }
 
   class RootLens[C] extends Lens[C, C] {
@@ -245,10 +245,10 @@ object MkFieldLens {
   implicit def mkFieldLens[A, K, R <: HList, B]
     (implicit
       mkGen: MkLabelledGenericLens.Aux[A, R],
-      mkLens: MkRecordSelectLens[R, K]): Aux[A, K, mkLens.Elem] =
+      mkLens: MkRecordSelectLens.Aux[R, K, B]): Aux[A, K, B] =
         new MkFieldLens[A, K] {
-          type Elem = mkLens.Elem
-          def apply(): Lens[A, mkLens.Elem] = mkLens() compose mkGen()
+          type Elem = B
+          def apply(): Lens[A, B] = mkLens() compose mkGen()
         }
 }
 
diff --git a/core/shared/src/main/scala/shapeless/ops/hlists.scala b/core/shared/src/main/scala/shapeless/ops/hlists.scala
index 0de769267..6930bcf8f 100644
--- a/core/shared/src/main/scala/shapeless/ops/hlists.scala
+++ b/core/shared/src/main/scala/shapeless/ops/hlists.scala
@@ -121,35 +121,35 @@ object hlist {
   object NatTRel {
     def apply[L1 <: HList, F1[_], L2 <: HList, F2[_]](implicit natTRel: NatTRel[L1, F1, L2, F2]) = natTRel
 
-    implicit def hnilNatTRel1[F1[_], F2[_]] = new NatTRel[HNil, F1, HNil, F2] {
+    implicit def hnilNatTRel1[F1[_], F2[_]]: NatTRel[HNil, F1, HNil, F2] = new NatTRel[HNil, F1, HNil, F2] {
       def map(f: F1 ~> F2, fa: HNil): HNil = HNil
     }
 
-    implicit def hnilNatTRel2[F1[_], H2] = new NatTRel[HNil, F1, HNil, Const[H2]#λ] {
+    implicit def hnilNatTRel2[F1[_], H2]: NatTRel[HNil, F1, HNil, Const[H2]#λ] = new NatTRel[HNil, F1, HNil, Const[H2]#λ] {
       def map(f: F1 ~> Const[H2]#λ, fa: HNil): HNil = HNil
     }
 
-    implicit def hlistNatTRel1[H, F1[_], F2[_], T1 <: HList, T2 <: HList](implicit nt : NatTRel[T1, F1, T2, F2]) =
+    implicit def hlistNatTRel1[H, F1[_], F2[_], T1 <: HList, T2 <: HList](implicit nt : NatTRel[T1, F1, T2, F2]): NatTRel[F1[H] :: T1, F1, F2[H] :: T2, F2] =
       new NatTRel[F1[H] :: T1, F1, F2[H] :: T2, F2] {
         def map(f: F1 ~> F2, fa: F1[H] :: T1): F2[H] :: T2 = f(fa.head) :: nt.map(f, fa.tail)
       }
 
-    implicit def hlistNatTRel2[H, F2[_], T1 <: HList, T2 <: HList](implicit nt : NatTRel[T1, Id, T2, F2]) =
+    implicit def hlistNatTRel2[H, F2[_], T1 <: HList, T2 <: HList](implicit nt : NatTRel[T1, Id, T2, F2]): NatTRel[H :: T1, Id, F2[H] :: T2, F2] =
       new NatTRel[H :: T1, Id, F2[H] :: T2, F2] {
         def map(f: Id ~> F2, fa: H :: T1): F2[H] :: T2 = f(fa.head) :: nt.map(f, fa.tail)
       }
 
-    implicit def hlistNatTRel3[H, F1[_], T1 <: HList, T2 <: HList](implicit nt : NatTRel[T1, F1, T2, Id]) =
+    implicit def hlistNatTRel3[H, F1[_], T1 <: HList, T2 <: HList](implicit nt : NatTRel[T1, F1, T2, Id]): NatTRel[F1[H] :: T1, F1, H :: T2, Id] =
       new NatTRel[F1[H] :: T1, F1, H :: T2, Id] {
         def map(f: F1 ~> Id, fa: F1[H] :: T1): H :: T2 = f(fa.head) :: nt.map(f, fa.tail)
       }
 
-    implicit def hlistNatTRel4[H1, F1[_], T1 <: HList, H2, T2 <: HList](implicit nt : NatTRel[T1, F1, T2, Const[H2]#λ]) =
+    implicit def hlistNatTRel4[H1, F1[_], T1 <: HList, H2, T2 <: HList](implicit nt : NatTRel[T1, F1, T2, Const[H2]#λ]): NatTRel[F1[H1] :: T1, F1, H2 :: T2, Const[H2]#λ] =
       new NatTRel[F1[H1] :: T1, F1, H2 :: T2, Const[H2]#λ] {
         def map(f: F1 ~> Const[H2]#λ, fa: F1[H1] :: T1): H2 :: T2 = f(fa.head) :: nt.map(f, fa.tail)
       }
 
-    implicit def hlistNatTRel5[H1, T1 <: HList, H2, T2 <: HList](implicit nt : NatTRel[T1, Id, T2, Const[H2]#λ]) =
+    implicit def hlistNatTRel5[H1, T1 <: HList, H2, T2 <: HList](implicit nt : NatTRel[T1, Id, T2, Const[H2]#λ]): NatTRel[H1 :: T1, Id, H2 :: T2, Const[H2]#λ] =
       new NatTRel[H1 :: T1, Id, H2 :: T2, Const[H2]#λ] {
         def map(f: Id ~> Const[H2]#λ, fa: H1 :: T1): H2 :: T2 = f(fa.head) :: nt.map(f, fa.tail)
       }
@@ -214,12 +214,12 @@ object hlist {
 
     type Aux[L <: HList, Out0 <: HKernel] = HKernelAux[L] { type Out = Out0 }
 
-    implicit def mkHNilHKernel = new HKernelAux[HNil] {
+    implicit def mkHNilHKernel: Aux[HNil, HNilHKernel] = new HKernelAux[HNil] {
       type Out = HNilHKernel
       def apply() = HNilHKernel
     }
 
-    implicit def mkHListHKernel[H, T <: HList, CtOut <: HKernel](implicit ct: HKernelAux.Aux[T, CtOut]) = new HKernelAux[H :: T] {
+    implicit def mkHListHKernel[H, T <: HList, CtOut <: HKernel](implicit ct: HKernelAux.Aux[T, CtOut]): Aux[H :: T, HConsHKernel[H, CtOut]] = new HKernelAux[H :: T] {
       type Out = HConsHKernel[H, CtOut]
       def apply() = HConsHKernel[H, CtOut](ct())
     }
@@ -2740,7 +2740,7 @@ object hlist {
       type Aux[L <: HList, V, P <: Poly, Out0 <: HList] = RightScanner0[L, V, P] { type Out = Out0 }
     }
 
-    implicit def hlistRightScanner0[H, H0, T <: HList, P <: Poly, C2Result](implicit ev: Case2.Aux[P, H0, H, C2Result]) =
+    implicit def hlistRightScanner0[H, H0, T <: HList, P <: Poly, C2Result](implicit ev: Case2.Aux[P, H0, H, C2Result]): RightScanner0.Aux[H :: T, H0, P, C2Result :: H :: T] =
       new RightScanner0[H :: T, H0, P]{
         type Out = C2Result :: H :: T
 
@@ -2845,7 +2845,7 @@ object hlist {
         }
 
     implicit def hlistPatch2[M <: Nat, L <: HList, In <: HList, OutL <: HList, OutP <: HList]
-      (implicit drop: Drop.Aux[L, M, OutL], prepend: Prepend.Aux[In, OutL, OutP]) =
+      (implicit drop: Drop.Aux[L, M, OutL], prepend: Prepend.Aux[In, OutL, OutP]): Patcher.Aux[_0, M, L, In, OutP] =
         new Patcher[_0, M, L, In]{
           type Out = OutP
 
@@ -3049,7 +3049,7 @@ object hlist {
   }
 
   trait LowPriorityCombinations {
-    implicit def combinationHNil[N <: Nat] =
+    implicit def combinationHNil[N <: Nat]: Combinations.Aux[N, HNil, HNil] =
       new Combinations[N, HNil] {
         type Out = HNil
         def apply(l: HNil): Out = HNil
diff --git a/core/shared/src/main/scala/shapeless/ops/nat.scala b/core/shared/src/main/scala/shapeless/ops/nat.scala
index 6f5502683..e6b100e4d 100644
--- a/core/shared/src/main/scala/shapeless/ops/nat.scala
+++ b/core/shared/src/main/scala/shapeless/ops/nat.scala
@@ -140,14 +140,14 @@ object nat {
   object LT extends LT0 {
     def apply[A <: Nat, B <: Nat](implicit lt: A < B): LT[A, B] = lt
 
-    implicit def lt1[B <: Nat] = new <[_0, Succ[B]] {}
-    implicit def lt2[A <: Nat, B <: Nat](implicit lt : A < B) = new <[Succ[A], Succ[B]] {}
+    implicit def lt1[B <: Nat]: _0 < Succ[B] = new <[_0, Succ[B]] {}
+    implicit def lt2[A <: Nat, B <: Nat](implicit lt : A < B): Succ[A] < Succ[B] = new <[Succ[A], Succ[B]] {}
   }
 
   trait LT0 {
     type <[A <: Nat, B <: Nat] = LT[A, B]
 
-    implicit def lt3[A <: Nat] = new <[A, Succ[A]] {}
+    implicit def lt3[A <: Nat]: A < Succ[A] = new <[A, Succ[A]] {}
   }
 
   /**
@@ -160,15 +160,15 @@ object nat {
   object LTEq extends LTEq0 {
     def apply[A <: Nat, B <: Nat](implicit lteq: A <= B): LTEq[A, B] = lteq
 
-    implicit def ltEq1[A <: Nat] = new <=[A, A] {}
-    implicit def ltEq2[A <: Nat] = new <=[A, Succ[A]] {}
+    implicit def ltEq1[A <: Nat]: A <= A = new <=[A, A] {}
+    implicit def ltEq2[A <: Nat]: A <= Succ[A] = new <=[A, Succ[A]] {}
   }
 
   trait LTEq0 {
     type <=[A <: Nat, B <: Nat] = LTEq[A, B]
 
-    implicit def ltEq3[B <: Nat] = new <=[_0, B] {}
-    implicit def ltEq4[A <: Nat, B <: Nat](implicit lteq : A <= B) = new <=[Succ[A], Succ[B]] {}
+    implicit def ltEq3[B <: Nat]: _0 <= B = new <=[_0, B] {}
+    implicit def ltEq4[A <: Nat, B <: Nat](implicit lteq : A <= B): Succ[A] <= Succ[B] = new <=[Succ[A], Succ[B]] {}
   }
 
   /**
diff --git a/core/shared/src/main/scala/shapeless/ops/tuples.scala b/core/shared/src/main/scala/shapeless/ops/tuples.scala
index e1eb014eb..ec735601a 100644
--- a/core/shared/src/main/scala/shapeless/ops/tuples.scala
+++ b/core/shared/src/main/scala/shapeless/ops/tuples.scala
@@ -1243,7 +1243,7 @@ object tuple {
       (implicit gen: Generic.Aux[T, L],
         genIn: Generic.Aux[InT, InL],
         patch: hl.Patcher.Aux[N, M, L, InL, OutL],
-        tp: hl.Tupler[OutL]) =
+        tp: hl.Tupler[OutL]): Patcher[N, M, T, InT] { type Out = tp.Out } =
         new Patcher[N, M, T, InT]{
           type Out = tp.Out
 
diff --git a/core/shared/src/main/scala/shapeless/poly.scala b/core/shared/src/main/scala/shapeless/poly.scala
index c3add45cc..cd73c6ddf 100644
--- a/core/shared/src/main/scala/shapeless/poly.scala
+++ b/core/shared/src/main/scala/shapeless/poly.scala
@@ -73,7 +73,7 @@ object PolyDefns extends Cases {
 
   object Compose {
     implicit def composeCase[C, F <: Poly, G <: Poly, T, U, V]
-      (implicit unpack: Unpack2[C, Compose, F, G], cG : Case1.Aux[G, T, U], cF : Case1.Aux[F, U, V]) = new Case[C, T :: HNil] {
+      (implicit unpack: Unpack2[C, Compose, F, G], cG : Case1.Aux[G, T, U], cF : Case1.Aux[F, U, V]): Case.Aux[C, T :: HNil, V] = new Case[C, T :: HNil] {
       type Result = V
       val value = (t : T :: HNil) => cF(cG.value(t))
     }
@@ -170,11 +170,11 @@ object PolyDefns extends Cases {
    * Base class for lifting a `Function1` to a `Poly1`
    */
   class ->[T, R](f : T => R) extends Poly1 {
-    implicit def subT[U <: T] = at[U](f)
+    implicit def subT[U <: T]: Case.Aux[U, R] = at[U](f)
   }
 
   trait LowPriorityLiftFunction1 extends Poly1 {
-    implicit def default[T] = at[T](_ => HNil : HNil)
+    implicit def default[T]: Case.Aux[T, HNil] = at[T](_ => HNil : HNil)
   }
 
   /**
@@ -182,11 +182,11 @@ object PolyDefns extends Cases {
    * its only element if the argument is in the original functions domain, `HNil` otherwise.
    */
   class >->[T, R](f : T => R) extends LowPriorityLiftFunction1 {
-    implicit def subT[U <: T] = at[U](f(_) :: HNil)
+    implicit def subT[U <: T]: Case.Aux[U, R :: HNil] = at[U](f(_) :: HNil)
   }
 
   trait LowPriorityLiftU extends Poly {
-    implicit def default[L <: HList] = new ProductCase[L] {
+    implicit def default[L <: HList]: ProductCase.Aux[L, HNil] = new ProductCase[L] {
       type Result = HNil
       val value = (l : L) => HNil
     }
@@ -197,7 +197,7 @@ object PolyDefns extends Cases {
    * only element if the argument is in the original functions domain, `HNil` otherwise.
    */
   class LiftU[P <: Poly](p : P)  extends LowPriorityLiftU {
-    implicit def defined[L <: HList](implicit caseT : Case[P, L]) = new ProductCase[L] {
+    implicit def defined[L <: HList](implicit caseT : Case[P, L]): ProductCase.Aux[L, caseT.Result :: HNil] = new ProductCase[L] {
       type Result = caseT.Result :: HNil
       val value = (l : L) => caseT(l) :: HNil
     }
diff --git a/core/shared/src/main/scala/shapeless/syntax/std/functions.scala b/core/shared/src/main/scala/shapeless/syntax/std/functions.scala
index 5aa6e1e39..0c1ae3189 100644
--- a/core/shared/src/main/scala/shapeless/syntax/std/functions.scala
+++ b/core/shared/src/main/scala/shapeless/syntax/std/functions.scala
@@ -29,12 +29,12 @@ package std
 object function {
   import ops.function._
 
-  implicit def fnHListOps[F, T <: HList, R](t: F)(implicit fnHLister: FnToProduct.Aux[F, T => R]) = new FnHListOps[T => R] {
+  implicit def fnHListOps[F, T <: HList, R](t: F)(implicit fnHLister: FnToProduct.Aux[F, T => R]): FnHListOps[T => R] = new FnHListOps[T => R] {
     def toProduct = fnHLister(t)
   }
 
 
-  implicit def fnUnHListOps[F](t : F)(implicit fnUnHLister : FnFromProduct[F]) = new FnUnHListOps[fnUnHLister.Out] {
+  implicit def fnUnHListOps[F](t : F)(implicit fnUnHLister : FnFromProduct[F]): FnUnHListOps[fnUnHLister.Out] = new FnUnHListOps[fnUnHLister.Out] {
     def fromProduct = fnUnHLister(t)
   }
 }
diff --git a/core/shared/src/main/scala/shapeless/syntax/std/maps.scala b/core/shared/src/main/scala/shapeless/syntax/std/maps.scala
index 65cf90fd7..ba85c3b4e 100644
--- a/core/shared/src/main/scala/shapeless/syntax/std/maps.scala
+++ b/core/shared/src/main/scala/shapeless/syntax/std/maps.scala
@@ -23,7 +23,7 @@ import shapeless.ops.maps.FromMap
  * Conversions between `Map` and `Records`.
  */
 object maps {
-  implicit def mapOps[K, V](m: Map[K, V]) = new MapOps[K, V](m)
+  implicit def mapOps[K, V](m: Map[K, V]): MapOps[K, V] = new MapOps[K, V](m)
 }
 
 final class MapOps[K, V](m: Map[K, V]) {
diff --git a/core/shared/src/main/scala/shapeless/syntax/zipper.scala b/core/shared/src/main/scala/shapeless/syntax/zipper.scala
index 1fb1eb5bf..1de1c3062 100644
--- a/core/shared/src/main/scala/shapeless/syntax/zipper.scala
+++ b/core/shared/src/main/scala/shapeless/syntax/zipper.scala
@@ -18,8 +18,8 @@ package shapeless
 package syntax
 
 object zipper {
-  implicit def toZipper[L <: HList](l: L) = new HListZipperOps(l)
-  implicit def toZipper[C, CL <: HList](c : C)(implicit gen : Generic.Aux[C, CL]) = new GenericZipperOps(c)
+  implicit def toZipper[L <: HList](l: L): HListZipperOps[L] = new HListZipperOps(l)
+  implicit def toZipper[C, CL <: HList](c : C)(implicit gen : Generic.Aux[C, CL]): GenericZipperOps[C, CL] = new GenericZipperOps(c)
 }
 
 /** Enhances values of any type with a representation via `Generic` with a method supporting conversion to a `Zipper`. */
diff --git a/core/shared/src/main/scala/shapeless/typeoperators.scala b/core/shared/src/main/scala/shapeless/typeoperators.scala
index 98e731db4..1f26b83d4 100644
--- a/core/shared/src/main/scala/shapeless/typeoperators.scala
+++ b/core/shared/src/main/scala/shapeless/typeoperators.scala
@@ -195,7 +195,7 @@ trait Lub[-A, -B, Out] extends Serializable {
 }
 
 object Lub {
-  implicit def lub[T] = new Lub[T, T, T] {
+  implicit def lub[T]: Lub[T, T, T] = new Lub[T, T, T] {
     def left(a : T): T = a
     def right(b : T): T = b
   }
diff --git a/core/shared/src/main/scala/shapeless/unwrapped.scala b/core/shared/src/main/scala/shapeless/unwrapped.scala
index bedf51ada..ef8674d04 100644
--- a/core/shared/src/main/scala/shapeless/unwrapped.scala
+++ b/core/shared/src/main/scala/shapeless/unwrapped.scala
@@ -34,7 +34,7 @@ trait UnwrappedInstances extends LowPriorityUnwrappedInstances {
     gen: Generic.Aux[W, Repr],
     avh: AnyValHelper.Aux[Repr, UI],
     chain: Strict[Unwrapped.Aux[UI, UF]]
-  ) = new Unwrapped[W] {
+  ): Unwrapped.Aux[W, UF] = new Unwrapped[W] {
     type U = UF
     def unwrap(w: W): U = chain.value.unwrap(avh.unwrap(gen.to(w)))
     def wrap(u: U): W = gen.from(avh.wrap(chain.value.wrap(u)))
@@ -47,7 +47,7 @@ trait UnwrappedInstances extends LowPriorityUnwrappedInstances {
   }
   object AnyValHelper {
     type Aux[Repr, U0] = AnyValHelper[Repr] { type U = U0 }
-    implicit def sizeOneHListHelper[T] =
+    implicit def sizeOneHListHelper[T]: Aux[T :: HNil, T] =
       SizeOneHListHelper.asInstanceOf[AnyValHelper.Aux[T :: HNil, T]]
     val SizeOneHListHelper = new AnyValHelper[Any :: HNil] {
       type U = Any
@@ -58,11 +58,11 @@ trait UnwrappedInstances extends LowPriorityUnwrappedInstances {
 
   implicit def newtypeUnwrapped[UI, Ops, UF](implicit
     chain: Strict[Unwrapped.Aux[UI, UF]]
-  ) = chain.value.asInstanceOf[Unwrapped.Aux[Newtype[UI, Ops], UF]]
+  ): Unwrapped.Aux[Newtype[UI, Ops], UF] = chain.value.asInstanceOf[Unwrapped.Aux[Newtype[UI, Ops], UF]]
 
   implicit def tagUnwrapped[T[UI, TT] <: tag.@@[UI, TT], UI, TT, UF](implicit
     chain: Strict[Unwrapped.Aux[UI, UF]]
-  ) = chain.value.asInstanceOf[Unwrapped.Aux[T[UI, TT], UF]]
+  ): Unwrapped.Aux[T[UI, TT], UF] = chain.value.asInstanceOf[Unwrapped.Aux[T[UI, TT], UF]]
 
 }
 
@@ -73,6 +73,6 @@ trait LowPriorityUnwrappedInstances {
       def unwrap(t: Any) = t
       def wrap(t: Any) = t
     }
-  implicit def selfUnwrapped[T] =
+  implicit def selfUnwrapped[T]: Unwrapped.Aux[T,T] =
     theSelfUnwrapped.asInstanceOf[Unwrapped.Aux[T, T]]
 }
diff --git a/core/shared/src/test/scala/shapeless/generic.scala b/core/shared/src/test/scala/shapeless/generic.scala
index a5cf69928..9aa6610d6 100644
--- a/core/shared/src/test/scala/shapeless/generic.scala
+++ b/core/shared/src/test/scala/shapeless/generic.scala
@@ -171,6 +171,13 @@ package GenericTestsAux {
     def apply(y: String): Priv = new Priv(y)
     def unapply(p: Priv): Some[String] = Some(p.y)
   }
+
+  object macroAnnotations {
+    case class A(i: Int, s: String)
+
+    @generateGeneric
+    object A
+  }
 }
 
 class GenericTests {
diff --git a/coreTestMacros/shared/src/main/scala/shapeless/generateGeneric.scala b/coreTestMacros/shared/src/main/scala/shapeless/generateGeneric.scala
new file mode 100644
index 000000000..3f4000fc9
--- /dev/null
+++ b/coreTestMacros/shared/src/main/scala/shapeless/generateGeneric.scala
@@ -0,0 +1,35 @@
+package shapeless
+
+import scala.annotation.{StaticAnnotation, compileTimeOnly}
+import scala.reflect.macros.blackbox
+import scala.language.experimental.macros
+
+@compileTimeOnly("enable macro annotations")
+class generateGeneric extends StaticAnnotation {
+  def macroTransform(annottees: Any*): Any = macro GenerateGenericMacroImpl.macroTransformImpl
+}
+
+object GenerateGenericMacroImpl {
+  def macroTransformImpl(c: blackbox.Context)(annottees: c.Tree*): c.Tree = {
+    import c.universe._
+
+    def modifyObject(obj: Tree): Tree = obj match {
+      case q"$mods object $tname extends { ..$earlydefns } with ..$parents { $self => ..$body }" =>
+        q"""$mods object $tname extends { ..$earlydefns } with ..$parents { $self =>
+          ..$body
+          _root_.shapeless.Generic[${tname.toTypeName}](_root_.shapeless.Generic.materialize)
+        }"""
+      case _ => sys.error("impossible")
+    }
+
+    def modify(cls: Tree, obj: Tree): Tree = q"..${Seq(cls, modifyObject(obj))}"
+
+    annottees match {
+      case (cls: ClassDef) :: (obj: ModuleDef) :: Nil => modify(cls, obj)
+      case (cls: ClassDef) :: Nil => modify(cls, q"object ${cls.name.toTermName}")
+      // this works for the companion object of a sealed trait or top-level case class but not nested case class
+      case (obj: ModuleDef) :: Nil => modifyObject(obj)
+      case _ => c.abort(c.enclosingPosition, "@generateGeneric can annotate only traits, classes, and objects")
+    }
+  }
+}
\ No newline at end of file