Merge pull request #14894 from dotty-staging/fix-11097

Author: dwijnand

compiler/src/dotty/tools/dotc/transform/TypeTestsCasts.scala

@@ -151,6 +151,7 @@ object TypeTestsCasts {
       case OrType(tp1, tp2)     => recur(X, tp1) && recur(X, tp2)
       case AnnotatedType(t, _)  => recur(X, t)
       case tp2: RefinedType     => recur(X, tp2.parent) && TypeComparer.hasMatchingMember(tp2.refinedName, X, tp2)
+      case tp2: RecType         => recur(X, tp2.parent)
       case _                    => true
     })
 

tests/neg-custom-args/fatal-warnings/i11097.scala

@@ -0,0 +1,13 @@
+@main def test: Unit = {
+  class C { type T1; type T2 }
+
+  def pmatch(s: C): s.T2 = s match {
+    case p: (C { type T1 = Int; type T2 >: T1  } & s.type) =>  // error
+      (3: p.T1): p.T2
+    case p: (C { type T1 = String; type T2 >: T1  } & s.type) =>  // error
+      ("this branch should be matched": p.T1): p.T2
+  }
+
+  // ClassCastException: class java.lang.Integer cannot be cast to class java.lang.String
+  val x = pmatch(new C { type T1 = String; type T2 = String })
+}