Back off failing refineUsingParent

Turns out to be too strict.

Author: dwijnand

compiler/src/dotty/tools/dotc/core/TypeOps.scala

@@ -917,10 +917,8 @@ object TypeOps:
     }
 
     def instantiate(): Type = {
-      var failedMixin = false
       for tp <- mixins.reverseIterator do
-        failedMixin ||= !(protoTp1 <:< tp)
-      if failedMixin then return NoType
+        protoTp1 <:< tp
       maximizeType(protoTp1, NoSpan)
       wildApprox(protoTp1)
     }

tests/pos/i19031.ci-reg1.scala

@@ -10,3 +10,7 @@ class Test:
   def t1(foo: Foo[Int]): Unit = foo match
     case _: Mark[t] =>
     case _          =>
+
+  def t2[F <: Foo[Int]](foo: F): Unit = foo match
+    case _: Mark[t] =>
+    case _          =>

tests/pos/i19031.ci-reg2.scala

@@ -1,3 +1,5 @@
+//> using options -Werror
+
 trait Outer:
   sealed trait Foo
   case class  Bar1() extends Foo