Fix compiler crash in WUnused

Author: szymon-rd

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

@@ -47,7 +47,8 @@ class CheckUnused private (phaseMode: CheckUnused.PhaseMode, suffix: String, _ke
 
   override def isRunnable(using Context): Boolean =
     ctx.settings.Wunused.value.nonEmpty &&
-    !ctx.isJava
+    !ctx.isJava &&
+    super.isRunnable
 
   // ========== SETUP ============
 

tests/neg-custom-args/fatal-warnings/i17335.scala

@@ -0,0 +1,4 @@
+// scalac: -Wunused:all
+
+def aMethod() =
+  doStuff { (x) => x } // error