Scala Predef unimport

Question

Possible Duplicate:
How to unimport String “+” operator in Scala?

So things from Predef get automatically imported into scala programs. But how can I disable- unimport certain or all imported functions from Predef? As an example if I don't like the '+' operator on String how to disable this functionality?

Also related: http://stackoverflow.com/questions/1668328/unimporting-in-scala. — missingfaktor, Oct 03 '11 at 11:01
Maybe a duplicate but I would still like to know how to *unimport* arbitrary import. — Tomasz Nurkiewicz, Oct 03 '11 at 11:02
The supposed "exact duplicate" question doesn't answer the question as well as @retronym's answer below. — ebruchez, Oct 03 '12 at 16:10

score 18 · Accepted Answer · answered Oct 03 '11 at 12:15

18

As mentioned in the linked answer, the method String#+(other: Any) is added to the String class with compiler magic, rather than with an implicit conversion. As such, it isn't related to the automatic import of Predef._.

The same applies to Int#+(x: String), and corresponding method on the other value types.

However, there is another String concatenation method that is added by an implicit conversion in Predef. x + "2" is treated as Predef.any2stringAdd(x).+("2"). By explicitly importing Predef on the first line of your file, you can rename unwanted members to _, disabling them.

import Predef.{any2stringadd => _, _}

object Test {    
  object A
  A + "20" // error: value + is not a member of object Test.A
}

I don't think that this works in Scala Scripts or in the REPL. There is also an unsupported option, -Yno-predef, to turn of the automatic import globally.

Related: SI-1931

answered Oct 03 '11 at 12:15

retronym

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Thanks! So another use case for te underscore. – AndreasScheinert Oct 03 '11 at 12:38
Doesn't seem to work in 2.10: `import Predef.{boolean2Boolean => _}` -> `[ERROR] Note that implicit conversions are not applicable because they are ambiguous: both method Boolean2boolean in object Predef of type (x: Boolean)Boolean and method safeBoolean2boolean are possible conversion functions from Boolean to Boolean` – Marius Soutier Feb 25 '14 at 14:25
3

Predef unimporting has to be done in a file (not in the REPL) and in the very first import. – retronym Mar 17 '14 at 11:53
2

SI-1931 lands in 2.11.8, apparently, so it will work in REPL. – som-snytt Nov 19 '15 at 07:08
It actually does work in the REPL in `2.11` and `2.12`. – Nader Ghanbari Jun 14 '18 at 17:56

Scala Predef unimport

1 Answers1

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