diff --git a/src/dotty/tools/dotc/core/TypeOps.scala b/src/dotty/tools/dotc/core/TypeOps.scala
index 70e8302d93dc..34febf3be689 100644
--- a/src/dotty/tools/dotc/core/TypeOps.scala
+++ b/src/dotty/tools/dotc/core/TypeOps.scala
@@ -266,31 +266,72 @@ trait TypeOps { this: Context => // TODO: Make standalone object.
         val accu1 = if (accu exists (_ derivesFrom c)) accu else c :: accu
         if (cs == c.baseClasses) accu1 else dominators(rest, accu1)
     }
-    if (ctx.featureEnabled(defn.LanguageModuleClass, nme.keepUnions)) tp
-    else tp match {
-      case tp: OrType =>
-        def isClassRef(tp: Type): Boolean = tp match {
-          case tp: TypeRef => tp.symbol.isClass
-          case tp: RefinedType => isClassRef(tp.parent)
-          case _ => false
-        }
-        def next(tp: TypeProxy) = tp.underlying match {
-          case TypeBounds(_, hi) => hi
-          case nx => nx
-        }
-        tp.tp1 match {
-          case tp1: TypeProxy if !isClassRef(tp1) =>
-            approximateUnion(next(tp1) | tp.tp2)
-          case _ =>
-            tp.tp2 match {
-              case tp2: TypeProxy if !isClassRef(tp2) =>
-                approximateUnion(tp.tp1 | next(tp2))
+    def approximateOr(tp1: Type, tp2: Type): Type = {
+      def isClassRef(tp: Type): Boolean = tp match {
+        case tp: TypeRef => tp.symbol.isClass
+        case tp: RefinedType => isClassRef(tp.parent)
+        case _ => false
+      }
+      def next(tp: TypeProxy) = tp.underlying match {
+        case TypeBounds(_, hi) => hi
+        case nx => nx
+      }
+      /** If `tp1` and `tp2` are typebounds, try to make one fit into the other
+       *  or to make them equal, by instantiating uninstantiated type variables.
+       */
+      def homogenizedUnion(tp1: Type, tp2: Type): Type = {
+        tp1 match {
+          case tp1: TypeBounds =>
+            tp2 match {
+              case tp2: TypeBounds =>
+                def fitInto(tp1: TypeBounds, tp2: TypeBounds): Unit = {
+                  val nestedCtx = ctx.fresh.setNewTyperState
+                  if (tp2.boundsInterval.contains(tp1.boundsInterval)(nestedCtx))
+                    nestedCtx.typerState.commit()
+                }
+                fitInto(tp1, tp2)
+                fitInto(tp2, tp1)
               case _ =>
-                val commonBaseClasses = tp.mapReduceOr(_.baseClasses)(intersect)
-                val doms = dominators(commonBaseClasses, Nil)
-                doms.map(tp.baseTypeWithArgs).reduceLeft(AndType.apply)
             }
+          case _ =>
         }
+        tp1 | tp2
+      }
+
+      tp1 match {
+        case tp1: RefinedType =>
+          tp2 match {
+            case tp2: RefinedType if tp1.refinedName == tp2.refinedName =>
+              return tp1.derivedRefinedType(
+                approximateUnion(OrType(tp1.parent, tp2.parent)),
+                tp1.refinedName,
+                homogenizedUnion(tp1.refinedInfo, tp2.refinedInfo).substRefinedThis(tp2, RefinedThis(tp1)))
+                //.ensuring { x => println(i"approx or $tp1 | $tp2 = $x\n constr = ${ctx.typerState.constraint}"); true } // DEBUG
+            case _ =>
+          }
+        case _ =>
+      }
+      tp1 match {
+        case tp1: TypeProxy if !isClassRef(tp1) =>
+          approximateUnion(next(tp1) | tp2)
+        case _ =>
+          tp2 match {
+            case tp2: TypeProxy if !isClassRef(tp2) =>
+              approximateUnion(tp1 | next(tp2))
+            case _ =>
+              val commonBaseClasses = tp.mapReduceOr(_.baseClasses)(intersect)
+              val doms = dominators(commonBaseClasses, Nil)
+              def baseTp(cls: ClassSymbol): Type =
+                if (tp1.typeParams.nonEmpty) tp.baseTypeRef(cls)
+                else tp.baseTypeWithArgs(cls)
+              doms.map(baseTp).reduceLeft(AndType.apply)
+          }
+      }
+    }
+    if (ctx.featureEnabled(defn.LanguageModuleClass, nme.keepUnions)) tp
+    else tp match {
+      case tp: OrType =>
+        approximateOr(tp.tp1, tp.tp2)
       case tp @ AndType(tp1, tp2) =>
         tp derived_& (approximateUnion(tp1), approximateUnion(tp2))
       case tp: RefinedType =>
diff --git a/src/dotty/tools/dotc/core/Types.scala b/src/dotty/tools/dotc/core/Types.scala
index 12c05b578915..47a4f088f754 100644
--- a/src/dotty/tools/dotc/core/Types.scala
+++ b/src/dotty/tools/dotc/core/Types.scala
@@ -1199,6 +1199,15 @@ object Types {
      *      class B extends C[B] with D with E
      *
      *  we approximate `A | B` by `C[A | B] with D`
+     *
+     *  As a second measure we also homogenize refinements containing
+     *  type variables. For instance, if `A` is an instantiatable type variable,
+     *  then
+     *
+     *      ArrayBuffer[Int] | ArrayBuffer[A]
+     *
+     *  is approximated by instantiating `A` to `Int` and returning `ArrayBuffer[Int]`
+     *  instead of `ArrayBuffer[_ >: Int | A <: Int & A]`
      */
     def approximateUnion(implicit ctx: Context) = ctx.approximateUnion(this)
 
@@ -2848,6 +2857,11 @@ object Types {
       case _ => super.| (that)
     }
 
+    /** The implied bounds, where aliases are mapped to intervals from
+     *  Nothing/Any
+     */
+    def boundsInterval(implicit ctx: Context): TypeBounds = this
+
     /** If this type and that type have the same variance, this variance, otherwise 0 */
     final def commonVariance(that: TypeBounds): Int = (this.variance + that.variance) / 2
 
@@ -2885,6 +2899,11 @@ object Types {
       else if (v < 0) derivedTypeAlias(this.lo & that.lo, v)
       else super.| (that)
     }
+
+    override def boundsInterval(implicit ctx: Context): TypeBounds =
+      if (variance == 0) this
+      else if (variance < 0) TypeBounds.lower(alias)
+      else TypeBounds.upper(alias)
   }
 
   class CachedTypeAlias(alias: Type, variance: Int, hc: Int) extends TypeAlias(alias, variance) {
diff --git a/tests/run/t5293-map.scala b/tests/disabled/run/t5293-map.scala
similarity index 100%
rename from tests/run/t5293-map.scala
rename to tests/disabled/run/t5293-map.scala
diff --git a/tests/pos/i1045.scala b/tests/pos/i1045.scala
new file mode 100644
index 000000000000..f5985af9235a
--- /dev/null
+++ b/tests/pos/i1045.scala
@@ -0,0 +1,7 @@
+import scala.collection._
+object T {
+  val newSymbolMap: mutable.HashMap[String, mutable.HashMap[Int, Double]] = mutable.HashMap.empty
+  val map = newSymbolMap.getOrElse("a", mutable.HashMap.empty)
+  map.put(1, 0.0)
+  newSymbolMap.put("a", map)
+}
diff --git a/tests/pos/intersection.scala b/tests/pos/intersection.scala
index 2b9f6c0b72ba..a4c19b5af406 100644
--- a/tests/pos/intersection.scala
+++ b/tests/pos/intersection.scala
@@ -1,3 +1,4 @@
+import dotty.language.keepUnions
 object intersection {
 
   class A
@@ -11,9 +12,6 @@ object intersection {
   val a: A & B => Unit = z
   val b: (A => Unit) | (B => Unit) = z
 
-
-
-
   type needsA = A => Nothing
   type needsB = B => Nothing
 }
diff --git a/tests/pending/run/vector1.check b/tests/run/vector1.check
similarity index 100%
rename from tests/pending/run/vector1.check
rename to tests/run/vector1.check
diff --git a/tests/pending/run/vector1.scala b/tests/run/vector1.scala
similarity index 100%
rename from tests/pending/run/vector1.scala
rename to tests/run/vector1.scala