Fix inline reduction for casedef guards with asInstanceOf

Author: jchyb

compiler/src/dotty/tools/dotc/inlines/InlineReducer.scala

@@ -364,6 +364,7 @@ class InlineReducer(inliner: Inliner)(using Context):
           if cdef.guard.isEmpty then (true, true)
           else typer.typed(cdef.guard.subst(from, to), defn.BooleanType) match {
             case ConstantValue(v: Boolean) => (v, true)
+            case Inlined(_, _, ConstantValue(v: Boolean)) => (v, true)
             case _ => (false, false)
           }
         if guardOK then Some((caseBindings.map(_.subst(from, to)), cdef.body.subst(from, to), canReduceGuard))

tests/pos/i22300.scala

@@ -0,0 +1,16 @@
+class Foo:
+
+  inline def inlineMatch[T]: String =
+    inline compiletime.erasedValue[T] match
+      case _: EmptyTuple               => ""
+      case _: (h *: _) if checkType[h](0) => ""
+
+  private inline def checkType[T](i: Int): Boolean =
+    inline compiletime.erasedValue[T] match
+      case _: Int => true
+      case _      => false
+
+val foo = Foo()
+
+@main def main () =
+  foo.inlineMatch[(Int, Boolean)]