Fix scala#9166: Harden check for values in patterns based on class inheritance info

Author: liufengyun

compiler/src/dotty/tools/dotc/typer/Typer.scala

@@ -3808,9 +3808,12 @@ class Typer extends Namer
               mapOver(tp)
         }
 
-        if tree.symbol.isOneOf(Module | Enum)
-           && !(tree.tpe frozen_<:< pt) // fast track
-           && !(tree.tpe frozen_<:< approx(pt))
+        val sym = tree.symbol
+
+        if !sym.info.classSymbol.asClass.mayHaveCommonChild(pt.classSymbol.asClass)
+           || sym.isOneOf(Module | Enum)
+              && !(tree.tpe frozen_<:< pt) // fast track
+              && !(tree.tpe frozen_<:< approx(pt))
         then
           // We could check whether `equals` is overriden.
           // Reasons for not doing so:

tests/neg/i9166.scala

@@ -0,0 +1,6 @@
+object UnitTest extends App {
+  def foo(m: Unit) = m match {
+    case runtime.BoxedUnit.UNIT => println("ok") // error
+  }
+  foo(())
+}