Closed
Description
the current type class derivation documentation covers generation of mirrors, however it is greatly simplified. As time has gone on since 3.0.0, the specification for when a mirror is generated has become more subtle.
Documentation should cover the precise rules for what kind of mirror is generated for each type T, and when a mirror is not able to be synthesized. It should also document how the binary API of the companion of T is affected by mirror generation.