Auto-tupling isn't spec'ed and should perhaps be deprecated (not just linted)

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From Typers:

/** Try packing all arguments into a Tuple and apply `fun'
           *  to that. This is the last thing which is tried (after
           *  default arguments)
           */

I couldn't find this in the spec.

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Imported From: https://issues.scala-lang.org/browse/SI-3583?orig=1
Reporter: @retronym

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@retronym said:
While we're at it, we could make this safer by:

• warning if auto tupling chooses one of overloaded alternatives
• warning if any auto-tupling occurs if -Xwarn-auto-tupling is specified.

[11:13pm] paulp: So I change from one joda time class with a 7-arg constructor to a similar one with fewer.
[11:13pm] paulp: but in addition to not having a 7-arg constructor, it has one which takes Object.
[11:14pm] paulp: so no warning until runtime failure "what the <expletive deleted> is a 7-tuple?" says joda time.
[11:14pm] paulp: that is an absolute debacle. 
[11:14pm] paulp: I knew about this issue but it never bit me this ugly before.
[11:16pm] retronym: -Xwarn-auto-tupling would be popular, from my straw polls
[11:19pm] retronym: paulp: or just outright disable it if there are overloaded alternatives

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@retronym said:
A warning could also be emitted if the target method is defined in Java.

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@retronym said:
See: http://thread.gmane.org/gmane.comp.lang.scala.debate/4954

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@paulp said:
There has been a warning available since scala/scala@4e488a60594 and the warning is included in -Xlint.

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@adriaanm said:
Not classifying as a spec bug, because I believe we should instead deprecate this. See also the discussion over at Dotty, where I hope this won't be implemented at all: scala/scala3#51