Verifies that From is NOT a subtype of To
Verifies that From is not identical to To
Helper class for !<:
Helper class for !=:=
Allow any two types fo !<:
Allow any two types fo !=:=
implicit that verifies !<:
implicit that verifies !=:=
Creates an ambigious implicit for From <: To to prevent that case.
Creates an ambigious implicit for From =:= To to prevent that case.