Also trust TypeTest when there is a Bind

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

@@ -457,17 +457,18 @@ object PatternMatcher {
       // begin patternPlan
       swapBind(tree) match {
         case Typed(pat, tpt) =>
-          val isTrusted = pat match {
+          def isTrusted(pattern: Tree): Boolean = pattern match {
             case UnApply(extractor, _, _) =>
               extractor.symbol.is(Synthetic)
               && extractor.symbol.owner.linkedClass.is(Case)
               && !hasExplicitTypeArgs(extractor)
+            case Bind(_, body) => isTrusted(body)
             case _ => false
           }
           val castTp = if Feature.ccEnabled
             then CapturingType(tpt.tpe, scrutinee.termRef.singletonCaptureSet)
             else tpt.tpe
-          TestPlan(TypeTest(tpt, isTrusted), scrutinee, tree.span,
+          TestPlan(TypeTest(tpt, isTrusted(pat)), scrutinee, tree.span,
             letAbstract(ref(scrutinee).cast(castTp)) { casted =>
               nonNull += casted
               patternPlan(casted, pat, onSuccess)

tests/pos/i24557.scala

@@ -0,0 +1,9 @@
+object test {
+  sealed trait X[T]
+  trait Iterable[T]
+  case class I[T, C <: Iterable[T]]() extends X[C]
+
+  def t[T](i: X[T]): Unit =
+    i match
+      case i @ I() => ()
+}