izumi.functional.bio.syntax

All implicit syntax in BIO is available automatically without wildcard imports with the help of so-called "implicit punning", as in the following example:

 import izumi.functional.bio.Monad2

 def loop[F[+_, +_]: Monad2]: F[Nothing, Nothing] = {
   val unitEffect: F[Nothing, Unit] = Monad2[F].unit
   unitEffect.flatMap(loop)
 }

Note that a .flatMap method is available on the unitEffect value of an abstract type parameter F, even though we did not import any syntax implicits using a wildcard import.

The flatMap method was added by the implicit punning on the Monad2 name. In short, implicit punning just means that instead of creating a companion object for a type with the same name as the type, we create "companion" implicit conversions with the same name. So that whenever you import the type, you are also always importing the syntax-providing implicit conversions.

This happens to be a great fit for Tagless Final Style, since nearly all TF code will import the names of the used typeclasses.

Implicit Punning for typeclass syntax relieves the programmer from having to manually import syntax implicits in every file in their codebase.