alehander92 / hatlog

hatlog

a proof of concept of a type inference tool for Python written in Prolog. Idea described in blog

currently it works for simple one-function python files

bin/hatlog examples/map.py
# A,B::Callable[[A],B] -> List[A] -> List[B]

hatlog flattens the python ast and annotates the types: constants for literals and variables otherwise
it generates a prolog program with the flattened ast: each node is represented as a prolog rule applied on its element types
the program imports the specified type system, infers the types of the function based on it and saves it
hatlog prints it

the type system is described as a simple file with prolog rules:

they describe the type rules for python nodes, e.g.

z_cmp(A, A, bool)     :- comparable(A).

z_index([list, X], int, X).
z_index([dict, X, Y], X, Y).
z_index(str, int, str).

and some builtin methods, e.g.

m([list, A], index, [A], int).

You can easily define your custom type systems just by tweaking those definitions.