Add extra isInstanceOf test cases

Author: dwijnand

tests/pos/i21544.scala

@@ -2,3 +2,12 @@ class Test():
   def m1(xs: List[Boolean]) = for (x: Any) <- xs yield x
   def m2(xs: List[Boolean]) = for (x: AnyVal) <- xs yield x
   def m3(xs: List[Boolean]) = for (x: Matchable) <- xs yield x
+
+  def v1(xs: List[AnyVal])    = for (x: Any) <- xs yield x
+  def v2(xs: List[AnyVal])    = for (x: AnyVal) <- xs yield x
+  def v3(xs: List[AnyVal])    = for (x: Matchable) <- xs yield x
+
+  def t1(xs: List[Matchable]) = for (x: Any) <- xs yield x
+  def t2(xs: List[Matchable]) = for (x: Matchable) <- xs yield x
+
+  def a1(xs: List[Any])       = for (x: Any) <- xs yield x