Undocumented(?) always available given: T => T

[Sporarum]

Hello,
I have discovered that the type T => T (for all T) is given, the following example compiles and run (scalaVersion := 3.0.2):

type A
def auto[T](using tt: T => T) = tt
@main def autoGiven = auto[A]

(doesn't compile if T => T is replaced by T)

This was unexpected, and I did not find any mention of it in the docs, for example there's no mention of it here:
https://docs.scala-lang.org/scala3/reference/contextual/givens.html

(I know as a rule you should wrap types in something to avoid unexpected givens like that, but for prototyping purposes I wasn't doing it)

The problem is not necessarily this unexpected behavior, rather that even having read documentation, it was still unexpected

Thank you for your time, hope this helps