deprecate or remove implicit in package object for Scala 3

[xuwei-k]

Scala 2 summon package object implicit values without imports. but Scala 3 does not.

This is confused 😇

Welcome to Scala 2.13.10 (OpenJDK 64-Bit Server VM, Java 11.0.18).
Type in expressions for evaluation. Or try :help.

scala> implicitly[com.github.tototoshi.csv.CSVFormat]
val res0: com.github.tototoshi.csv.CSVFormat = com.github.tototoshi.csv.package$$anon$1@47dabb27

Welcome to Scala 3.2.2 (11.0.18, Java OpenJDK 64-Bit Server VM).
Type in expressions for evaluation. Or try :help.
                                                                                                                                                                                                                                                           
scala> implicitly[com.github.tototoshi.csv.CSVFormat]
-- Error: ----------------------------------------------------------------------
1 |implicitly[com.github.tototoshi.csv.CSVFormat]
  |                                              ^
  |No given instance of type com.github.tototoshi.csv.CSVFormat was found for parameter e of method implicitly in object Predef
  |
  |The following import might fix the problem:
  |
  |  import com.github.tototoshi.csv.defaultCSVFormat

[tototoshi]

Indeed, I am also troubled by this issue. I currently have two ideas.

1. Deprecate the use of the package object and define defaultCSVFormat within a newly created CSVFormat object.
2. Define defaultCSVFormat within a newly created dedicated implicit object Hide implicit CSVFormat in dedicated object #71.

Both options are good, but I prefer option 1. Considering compatibility for users, adopting option 1 would allow most migrations without code changes. Option 2 is safer, though. Which do you think is better?

[xuwei-k]

• Scala 3 migration warning for implicits found in package prefix scala/scala#10621