Create a method definition def f[..](...) with the signature defined in the symbol.
Create a method definition def f[..](...) with the signature defined in the symbol.
The rhsFn is a function that receives references to its parameters and should return
Some containing the implementation of the method. Returns None the method has no implementation.
Any definition directly inside the implementation should have symbol as owner.
Use Symbol.asQuotes to create the rhs using quoted code.