[GitHub] [spark] som-snytt commented on pull request #32648: [WIP][SPARK-35496][BUILD] Upgrade Scala to 2.13.6

[GitBox <gi...@apache.org>]

som-snytt commented on pull request #32648:
URL: https://github.com/apache/spark/pull/32648#issuecomment-847756599


   Sample for wconf, where `i` says "info", `s` would be silence. It warns about deprecation but outer check is just info.
   ```
   ➜  snips scalac -d /tmp -Xlint "-Wconf:cat=unchecked&msg=outer reference:i" -Werror badcheck.scala
   badcheck.scala:11: warning: method g in class C is deprecated (since 0.1): bad g
     def x = g + 1
             ^
   badcheck.scala:7: The outer reference in this type test cannot be checked at run time.
       case _: U => true
             ^
   error: No warnings can be incurred under -Werror.
   1 warning
   1 error
   ➜  snips cat badcheck.scala
   
   class C {
     trait T
     trait U
   
     def f(t: T) = t match {
       case _: U => true
       case _ => false
     }
     @deprecated("bad g", "0.1") def g = 42
     def x = g + 1
   }
   ```
   I have to re-read `-Wconf:help` if I use it.


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