What precisely is a scala evidence parameter

Question

I\'ve been trying to find an authoritative definition of what is an evidence parameter, to no avail, for solving a case of \"could not find implicit value for evidence parameter

Answer 1

Scala evidence parameters are prepended to implicit parameter list.

def foo[A: M](implicit b: B): C
// expands to:
// def foo[A](implicit evidence$1: M[A], b: B): C

See specifications for more details. https://www.scala-lang.org/files/archive/spec/2.11/07-implicits.html