Fix exhaustivity checks

Author: liufengyun

compiler/test/dotty/tools/dotc/transform/PatmatExhaustivityTest.scala

@@ -18,7 +18,7 @@ import org.junit.Test
 class PatmatExhaustivityTest {
   val testsDir = "tests/patmat"
   // stop-after: patmatexhaust-huge.scala crash compiler
-  val options = List("-color:never", "-Ystop-after:crossCast", "-Ycheck-all-patmat", "-classpath", TestConfiguration.basicClasspath)
+  val options = List("-color:never", "-Ystop-after:explicitSelf", "-Ycheck-all-patmat", "-classpath", TestConfiguration.basicClasspath)
 
   private def compile(files: Seq[String]): Seq[String] = {
     val stringBuffer = new StringWriter()

tests/patmat/i4030.scala

@@ -9,5 +9,6 @@ object TestGADT {
   def f[A <: Seq[_], B, Foo >: A => B](v: Root[Foo], u: Root[Foo]) = (v, u) match {
     case (C3(), C3()) =>
   }
-  f(C3[Seq[_], Long](), C4[Seq[_], Long]())
+  // The following line no longer type checks
+  // f(C3[Seq[_], Long](), C4[Seq[_], Long]())
 }