etylizer

Static typechecker for Erlang based on set-theoretic types.

User-level documentation

make or rebar3 escripize will generate a standalone portable escript called ety inside the directory _build/default/bin
ety -h for help
- if ety is not on the current path, then prepend the folder where ety is located: $PATH_TO_ETY/ety -h
To check a single module file hello.erl execute ety hello.erl
To check a rebar project hello.erl
- compile the project (e.g. rebar3 compile)
- execute ety -P . -S src while in the root of the project

Useful for debugging:

ety hello.erl --force -l debug -o foo1/1

type checks only the function foo/1 (-o) with additional debug information (-l)
disables caching of results, i.e. force type checking (--force)

Parse, using erlang's parser.
Transform the AST into an internal representation. The AST for the internal representation is somewhat simpler and has the following properties:
- All names of local variable are unique.
- Variable occurences have been resolved so that we know whether a variable occurrence introduces a new binding or refers to an existing binding and in which module the existing binding is defined.
- Bounds in type definitions have been replaced by intersections.
Perform several sanity checks
- Check that type defs are regular and contractive. This requires constructing a dependency cycle and potentially loading of type defs from other modules.
- Check that we have a type signature for all non-local functions. This requires loading type specs from external modules. We also need type spec for all bifs and for all erlang modules.
- Check that each top-level functions have a type spec.

Make sure every top-level function has a type annotation.
Make sure every module has a short description at the top of the file stating the purpose of the module.
Make sure that complicated functions have a short text of documentation.
Make sure that complicated functions have unit tests.
Make sure that all unit tests are running before comitting: make test
Make sure the dialyzer is happy before comitting: make check