Featherweight Generic Go (FGG) is a minimal core calculus modeling the
essential features of the programming language Go. It includes support for
overloaded methods, interface types, structural subtyping and generics. The
most straightforward semantic description of the dynamic behavior of FGG
programs is to resolve method calls based on runtime type information of the
receiver.
This article shows a different approach by defining a type-directed
translation from FGG to an untyped lambda-calculus. The translation of an FGG
program provides evidence for the availability of methods as additional
dictionary parameters, similar to the dictionary-passing approach known from
Haskell type classes. Then, method calls can be resolved by a simple lookup of
the method definition in the dictionary.
Every program in the image of the translation has the same dynamic semantics
as its source FGG program. The proof of this result is based on a syntactic,
step-indexed logical relation. The step-index ensures a well-founded definition
of the relation in the presence of recursive interface types and recursive
methods.Comment: Submitted to JFP. 58 pages, includes appendix with full proof