fix default case recursion in child/parentTypeMap

Author: liufengyun

compiler/src/dotty/tools/dotc/transform/patmat/Space.scala

@@ -619,8 +619,8 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
             else this(hi)
           debug.println(s"$tp exposed to =====> $exposed")
           exposed
-        case _ =>
-          mapOver(t)
+        case tp =>
+          mapOver(tp)
       }
     }
 
@@ -638,8 +638,8 @@ class SpaceEngine(implicit ctx: Context) extends SpaceLogic {
 
           debug.println(s"$tp exposed to =====> $exposed")
           exposed
-        case _ =>
-          mapOver(t)
+        case tp =>
+          mapOver(tp)
       }
     }
 

tests/patmat/i3645f.check

@@ -0,0 +1 @@
+30: Pattern Match Exhaustivity: K1

tests/patmat/i3645f.scala

@@ -0,0 +1,36 @@
+object App {
+  def main(args: Array[String]): Unit = {
+    trait ModuleSig {
+      type U2
+      type U1
+
+      trait FooSig {
+        type Type = (U1 & U2)
+        def subst[F[_]](fa: F[Int]): F[Type]
+      }
+
+      val Foo: FooSig
+    }
+    val Module: ModuleSig = new ModuleSig {
+      type U1 = Int
+      type U2 = Int
+
+      val Foo: FooSig = new FooSig {
+        // type Type = Int
+        def subst[F[_]](fa: F[Int]): F[Type] = fa
+      }
+    }
+    type Foo = Module.Foo.Type
+
+    sealed abstract class K[F]
+    final case object K1 extends K[Int]
+    final case object K2 extends K[Foo]
+
+    val kv: K[Foo] = Module.Foo.subst[K](K1)
+    def test(k: K[Foo]): Unit = k match {
+      case K2 => ()
+    }
+
+    test(kv)
+  }
+}