➜  ~ scala -Wconf:cat=deprecation:e
Welcome to Scala 2.13.11 (OpenJDK 64-Bit Server VM, Java 20.0.1).
Type in expressions for evaluation. Or try :help.

scala> @deprecated("","") def f = 42

         lazy val $result = $line3.$read.INSTANCE.$iw.f
                                                      ^
<synthetic>:4: error: method f is deprecated

(To diagnose errors in synthetic code, try adding `// show` to the end of your input.)

scala> def f: String = 42
                       ^
       error: type mismatch;
        found   : Int(42)
        required: String

scala>