diff --git a/compiler/src/dotty/tools/dotc/transform/init/Checking.scala b/compiler/src/dotty/tools/dotc/transform/init/Checking.scala
index 85217501d55f..e47c3b08d264 100644
--- a/compiler/src/dotty/tools/dotc/transform/init/Checking.scala
+++ b/compiler/src/dotty/tools/dotc/transform/init/Checking.scala
@@ -326,14 +326,14 @@ object Checking {
 
           case Fun(pots, effs) =>
             val name = sym.name.toString
-            if (name == "apply") Summary(pots, Effects.empty)
-            else if (name == "tupled") Summary(Set(pot1), Effects.empty)
+            if (name == "apply") Summary(pots)
+            else if (name == "tupled") Summary(pot1)
             else if (name == "curried") {
               val arity = defn.functionArity(sym.info.finalResultType)
-              val pots = (1 until arity).foldLeft(Set(pot1)) { (acc, i) =>
-                Set(Fun(acc, Effects.empty)(pot1.source))
+              val pots = (1 until arity).foldLeft(Vector(pot1)) { (acc, i) =>
+                Vector(Fun(acc, Effects.empty)(pot1.source))
               }
-              Summary(pots, Effects.empty)
+              Summary(pots)
             }
             else Summary.empty
 
diff --git a/compiler/src/dotty/tools/dotc/transform/init/Effects.scala b/compiler/src/dotty/tools/dotc/transform/init/Effects.scala
index 9486263a8af0..ce9d8d8aa497 100644
--- a/compiler/src/dotty/tools/dotc/transform/init/Effects.scala
+++ b/compiler/src/dotty/tools/dotc/transform/init/Effects.scala
@@ -12,8 +12,8 @@ import core.Contexts._
 import Potentials._
 
 object Effects {
-  type Effects = Set[Effect]
-  val empty: Effects = Set.empty
+  type Effects = Vector[Effect]
+  val empty: Effects = Vector.empty
 
   def show(effs: Effects)(using Context): String =
     effs.map(_.show).mkString(", ")
@@ -25,13 +25,15 @@ object Effects {
     def show(using Context): String
 
     def source: Tree
+
+    def toEffs: Effects = Vector(this)
   }
 
-  /** An effect means that a value that's possibly under initialization
+  /** A promotion effect means that a value that's possibly under initialization
    *  is promoted from the initializing world to the fully-initialized world.
    *
    *  Essentially, this effect enforces that the object pointed to by
-   *  `potential` is fully initialized.
+   *  `potential` is transitively initialized.
    *
    *  This effect is trigger in several scenarios:
    *  - a potential is used as arguments to method calls or new-expressions
@@ -58,8 +60,6 @@ object Effects {
 
   // ------------------ operations on effects ------------------
 
-  extension (eff: Effect) def toEffs: Effects = Effects.empty + eff
-
   def asSeenFrom(eff: Effect, thisValue: Potential)(implicit env: Env): Effect =
     trace(eff.show + " asSeenFrom " + thisValue.show + ", current = " + currentClass.show, init, _.asInstanceOf[Effect].show) { eff match {
       case Promote(pot) =>
diff --git a/compiler/src/dotty/tools/dotc/transform/init/Potentials.scala b/compiler/src/dotty/tools/dotc/transform/init/Potentials.scala
index a7b409b56d5e..39eac29a2741 100644
--- a/compiler/src/dotty/tools/dotc/transform/init/Potentials.scala
+++ b/compiler/src/dotty/tools/dotc/transform/init/Potentials.scala
@@ -15,8 +15,8 @@ import Types._, Symbols._, Contexts._
 import Effects._, Summary._
 
 object Potentials {
-  type Potentials = Set[Potential]
-  val empty: Potentials = Set.empty
+  type Potentials = Vector[Potential]
+  val empty: Potentials = Vector.empty
 
   def show(pots: Potentials)(using Context): String =
     pots.map(_.show).mkString(", ")
@@ -31,6 +31,8 @@ object Potentials {
 
     def show(using Context): String
     def source: Tree
+
+    def toPots: Potentials = Vector(this)
   }
 
   sealed trait Refinable extends Potential {
@@ -153,8 +155,6 @@ object Potentials {
 
   // ------------------ operations on potentials ------------------
 
-  extension (pot: Potential) def toPots: Potentials = Potentials.empty + pot
-
   /** Selection on a set of potentials
    *
    *  @param ignoreSelectEffect Where selection effects should be ignored
diff --git a/compiler/src/dotty/tools/dotc/transform/init/Summarization.scala b/compiler/src/dotty/tools/dotc/transform/init/Summarization.scala
index 8df4cb7f558d..8da415bf82bb 100644
--- a/compiler/src/dotty/tools/dotc/transform/init/Summarization.scala
+++ b/compiler/src/dotty/tools/dotc/transform/init/Summarization.scala
@@ -107,7 +107,7 @@ object Summarization {
 
       case Typed(expr, tpt) =>
         if (tpt.tpe.hasAnnotation(defn.UncheckedAnnot)) Summary.empty
-        else analyze(expr)
+        else analyze(expr) ++ effectsOfType(tpt.tpe, tpt)
 
       case NamedArg(name, arg) =>
         analyze(arg)
@@ -140,7 +140,7 @@ object Summarization {
         val Summary(pots, effs) = analyze(selector)
         val init = Summary(Potentials.empty, pots.promote(selector) ++ effs)
         cases.foldLeft(init) { (acc, cas) =>
-          acc union analyze(cas.body)
+          acc + analyze(cas.body)
         }
 
       // case CaseDef(pat, guard, body) =>
@@ -162,7 +162,7 @@ object Summarization {
 
       case Try(block, cases, finalizer) =>
         val Summary(pots, effs) =  cases.foldLeft(analyze(block)) { (acc, cas) =>
-          acc union analyze(cas.body)
+          acc + analyze(cas.body)
         }
         val Summary(_, eff2) = if (finalizer.isEmpty) Summary.empty else analyze(finalizer)
         Summary(pots, effs ++ eff2)
@@ -199,8 +199,9 @@ object Summarization {
           Summary(pots.promote(ddef) ++ effs)
         }
 
-      case _: TypeDef =>
-        Summary.empty
+      case tdef: TypeDef =>
+        if tdef.isClassDef then Summary.empty
+        else Summary(effectsOfType(tdef.symbol.info, tdef.rhs))
 
       case _: Import | _: Export =>
         Summary.empty
@@ -213,6 +214,19 @@ object Summarization {
     else summary
   }
 
+  private def effectsOfType(tp: Type, source: Tree)(implicit env: Env): Effects =
+    var summary = Summary.empty
+    val traverser = new TypeTraverser {
+      def traverse(tp: Type): Unit = tp match {
+        case TermRef(_: SingletonType, _) =>
+          summary = summary + analyze(tp, source)
+        case _ =>
+          traverseChildren(tp)
+      }
+    }
+    traverser.traverse(tp)
+    summary.effs
+
   def analyze(tp: Type, source: Tree)(implicit env: Env): Summary =
   trace("summarizing " + tp.show, init, s => s.asInstanceOf[Summary].show) {
     val summary: Summary = tp match {
@@ -243,8 +257,12 @@ object Summarization {
         }
         Summary(pots2, effs)
 
+      case _: TermParamRef | _: RecThis  =>
+        // possible from checking effects of types
+        Summary.empty
+
       case _ =>
-        throw new Exception("unexpected type: " + tp.show)
+        throw new Exception("unexpected type: " + tp)
     }
 
     if (env.isAlwaysInitialized(tp)) Summary(Potentials.empty, summary.effs)
@@ -290,7 +308,7 @@ object Summarization {
       def parentArgEffsWithInit(stats: List[Tree], ctor: Symbol, source: Tree): Effects =
         val init =
           if env.canIgnoreMethod(ctor) then Effects.empty
-          else Effects.empty + MethodCall(ThisRef()(source), ctor)(source)
+          else Effects.empty :+ MethodCall(ThisRef()(source), ctor)(source)
         stats.foldLeft(init) { (acc, stat) =>
           val summary = Summarization.analyze(stat)
           acc ++ summary.effs
@@ -320,7 +338,7 @@ object Summarization {
                 if tref.prefix == NoPrefix then Effects.empty
                 else Summarization.analyze(tref.prefix, ref).effs
 
-              prefixEff +  MethodCall(ThisRef()(ref), ctor)(ref)
+              prefixEff :+ MethodCall(ThisRef()(ref), ctor)(ref)
             }
         })
       }
diff --git a/compiler/src/dotty/tools/dotc/transform/init/Summary.scala b/compiler/src/dotty/tools/dotc/transform/init/Summary.scala
index d4b72d4c0214..1c7a852d4847 100644
--- a/compiler/src/dotty/tools/dotc/transform/init/Summary.scala
+++ b/compiler/src/dotty/tools/dotc/transform/init/Summary.scala
@@ -14,14 +14,14 @@ import config.Printers.init
 import Potentials._, Effects._, Util._
 
 case class Summary(pots: Potentials, effs: Effects) {
-  def union(summary2: Summary): Summary =
+  def +(summary2: Summary): Summary =
     Summary(pots ++ summary2.pots, this.effs ++ summary2.effs)
 
   def +(pot: Potential): Summary =
-    Summary(pots + pot, effs)
+    Summary(pots :+ pot, effs)
 
   def +(eff: Effect): Summary =
-    Summary(pots, effs + eff)
+    Summary(pots, effs :+ eff)
 
   def dropPotentials: Summary =
     Summary(Potentials.empty, effs)
@@ -44,14 +44,14 @@ case class Summary(pots: Potentials, effs: Effects) {
 object Summary {
   val empty: Summary = Summary(Potentials.empty, Effects.empty)
 
-  def apply(pots: Potentials): Summary = new Summary(pots, Effects.empty)
+  def apply(pots: Potentials): Summary = empty ++ pots
 
   @targetName("withEffects")
-  def apply(effs: Effects): Summary = new Summary(Potentials.empty, effs)
+  def apply(effs: Effects): Summary = empty ++ effs
 
-  def apply(pot: Potential): Summary = new Summary(Potentials.empty + pot, Effects.empty)
+  def apply(pot: Potential): Summary = empty + pot
 
-  def apply(eff: Effect): Summary = new Summary(Potentials.empty, Effects.empty + eff)
+  def apply(eff: Effect): Summary = empty + eff
 }
 
 /** Summary of class.
diff --git a/tests/init/neg/i11572.scala b/tests/init/neg/i11572.scala
new file mode 100644
index 000000000000..c2ebe6fe47f9
--- /dev/null
+++ b/tests/init/neg/i11572.scala
@@ -0,0 +1,17 @@
+class A {
+  trait Cov[+X] {
+    def get: X
+  }
+  trait Bounded {
+    type T >: Cov[Int] <: Cov[String]
+  }
+  val t: Bounded = new Bounded {     // error
+    // Note: using this instead of t produces an error (as expected)
+    override type T >: t.T <: t.T
+  }
+
+  val covInt = new Cov[Int] {
+    override def get: Int = 3
+  }
+  val str: String = ((covInt: t.T): Cov[String]).get // ClassCastException: class Integer cannot be cast to class String
+}
diff --git a/tests/init/neg/i4031.scala b/tests/init/neg/i4031.scala
new file mode 100644
index 000000000000..8340296340e7
--- /dev/null
+++ b/tests/init/neg/i4031.scala
@@ -0,0 +1,10 @@
+object App {
+  trait A { type L >: Any}
+  def upcast(a: A, x: Any): a.L = x
+  val p: A { type L <: Nothing } = p        // error
+  def coerce(x: Any): Int = upcast(p, x)
+
+  def main(args: Array[String]): Unit = {
+    println(coerce("Uh oh!"))
+  }
+}
diff --git a/tests/init/neg/i4042.scala b/tests/init/neg/i4042.scala
new file mode 100644
index 000000000000..58c884a5690d
--- /dev/null
+++ b/tests/init/neg/i4042.scala
@@ -0,0 +1,18 @@
+object App {
+  def coerce[U, V](u: U): V = {
+    trait X { type R >: U }
+    trait Y { type R = V }
+
+    class T[A <: X](val a: A)(val value: a.R)
+
+    object O { val x : Y & X = x }  // error
+
+    val a = new T[Y & X](O.x)(u)
+    a.value
+  }
+
+  def main(args: Array[String]): Unit = {
+    val x: Int = coerce[String, Int]("a")
+    println(x + 1)
+  }
+}
diff --git a/tests/init/neg/i50.scala b/tests/init/neg/i50.scala
new file mode 100644
index 000000000000..9131fb263f48
--- /dev/null
+++ b/tests/init/neg/i50.scala
@@ -0,0 +1,5 @@
+class C[T] {
+  val a: T = method
+  def method = b
+  val b: T = a     // error
+}
\ No newline at end of file
diff --git a/tests/init/neg/i5854.scala b/tests/init/neg/i5854.scala
new file mode 100644
index 000000000000..a52685f63be2
--- /dev/null
+++ b/tests/init/neg/i5854.scala
@@ -0,0 +1,5 @@
+class B {
+  val a: String = (((1: Any): b.A): Nothing): String
+  val b: { type A >: Any <: Nothing } = loop()         // error
+  def loop(): Nothing = loop()
+}
diff --git a/tests/neg-strict/i5854.scala b/tests/neg-strict/i5854.scala
new file mode 100644
index 000000000000..e8c68105bbae
--- /dev/null
+++ b/tests/neg-strict/i5854.scala
@@ -0,0 +1,24 @@
+object bar {
+  trait Sub {
+    type M
+    type L <: M
+    type U >: M
+    type M2 >: L <: U
+  }
+  class Box[V](val v: V)
+
+  class Caster[LL, UU] {
+    trait S2 {
+      type L = LL
+      type U = UU
+    }
+    final lazy val nothing: Nothing = nothing
+    final lazy val sub: S2 & Sub = nothing
+    final lazy val box : Box[S2 & Sub] = new Box(nothing)
+    def upcast(t: box.v.M2): box.v.M2 = t  // error // error
+  }
+  def main(args : Array[String]) : Unit = {
+    val zero : String = (new Caster[Int,String]()).upcast(0)
+    println("...")
+  }
+}
\ No newline at end of file