diff --git a/compiler/src/dotty/tools/dotc/core/TypeComparer.scala b/compiler/src/dotty/tools/dotc/core/TypeComparer.scala
index 302ad7987889..b15a9cdb2444 100644
--- a/compiler/src/dotty/tools/dotc/core/TypeComparer.scala
+++ b/compiler/src/dotty/tools/dotc/core/TypeComparer.scala
@@ -543,7 +543,7 @@ class TypeComparer(@constructorOnly initctx: Context) extends ConstraintHandling
         recur(tp1.parent, tp2)
       case tp1: MatchType =>
         val reduced = tp1.reduced
-        if reduced.exists then
+        if reduced.exists && !reduced.isError then
           recur(reduced, tp2) && recordGadtUsageIf { MatchType.thatReducesUsingGadt(tp1) }
         else thirdTry
       case _: FlexType =>
@@ -786,7 +786,7 @@ class TypeComparer(@constructorOnly initctx: Context) extends ConstraintHandling
         either(recur(tp1, tp21), recur(tp1, tp22)) || fourthTry
       case tp2: MatchType =>
         val reduced = tp2.reduced
-        if reduced.exists then
+        if reduced.exists && !reduced.isError then
           recur(tp1, reduced) && recordGadtUsageIf { MatchType.thatReducesUsingGadt(tp2) }
         else
           fourthTry
diff --git a/tests/neg/i19949.scala b/tests/neg/i19949.scala
new file mode 100644
index 000000000000..96a22e42e079
--- /dev/null
+++ b/tests/neg/i19949.scala
@@ -0,0 +1,9 @@
+
+trait T[N]:
+  type M = N match
+    case 0 => Any
+
+val t: T[Double] = new T[Double] {}
+val x: t.M = "hello" // error
+
+val z: T[Double]#M = "hello" // error
diff --git a/tests/pos/i18211.scala b/tests/pos/i18211.scala
deleted file mode 100644
index c5ec30ba5d61..000000000000
--- a/tests/pos/i18211.scala
+++ /dev/null
@@ -1,39 +0,0 @@
-import scala.compiletime.ops.int.*
-
-type AnyInt[A <: Int] <: Int = A match {
-  case _ => A
-}
-
-type IndexOf[A, T <: Tuple] <: Int = T match {
-  case EmptyTuple => -1
-  case A *: t     => 0
-  case _ *: t =>
-    IndexOf[A, t] match {
-      case -1        => -1
-      case AnyInt[a] => S[a]
-    }
-}
-
-type Indexes[A, T <: Tuple]
-object Indexes {
-  given of[A, T <: Tuple](using IndexOf[A, T] >= 0 =:= true)(using
-      index: ValueOf[IndexOf[A, T]],
-      next: Indexes[A, Tuple.Drop[T, S[IndexOf[A, T]]]]
-  ): Indexes[A, T] = ???
-
-  given empty[A, T <: Tuple](using IndexOf[A, T] =:= -1): Indexes[A, T] = ???
-}
-
-class GetAll[A]:
-  def apply[T <: Tuple](t: T)(using indexes: Indexes[A, T]): List[A] = ???
-
-def getAll[A]: GetAll[A] = new GetAll[A]
-
-def test =
-  // the code here is trying to get all values from a tuple that has type [X] as a list
-
-  // this works if there are only two strings in the tuple
-  getAll[String](("str1", 1, "str2", false))
-
-  //but this not compiles if there are more than two strings in the tuple
-  getAll[String](("str1", 1, "str2", false, "str3"))
diff --git a/tests/pos/i19950.scala b/tests/pos/i19950.scala
new file mode 100644
index 000000000000..349140f43ff5
--- /dev/null
+++ b/tests/pos/i19950.scala
@@ -0,0 +1,10 @@
+
+trait Apply[F[_]]:
+  extension [T <: NonEmptyTuple](tuple: T)(using toMap: Tuple.IsMappedBy[F][T])
+    def mapN[B](f: Tuple.InverseMap[T, F] => B): F[B] = ???
+
+given Apply[Option] = ???
+given Apply[List] = ???
+given Apply[util.Try] = ???
+
+@main def Repro = (Option(1), Option(2), Option(3)).mapN(_ + _ + _)
\ No newline at end of file