ref: 2c2679ccab6f7903d670439e544ea3cbb74be25b dhall-ruby/test d---------
Refactor Optional/None typecheck
Refactor Function annotate
Run tests per docs
Use path like names in more tests
Implement integrity checks
Working typechecker
Type inference/checking about half done

Passing unit tests for features implemented so far
Support headers for HTTP import
Binary encoding

Every AST node uses as_json to express the generic structure for
encoding itself.  Expression aliases as_cbor to as_json by default and
then uses as_cbor in to_cbor (aliased as to_binary).

This design is because we need to override the encoding of Double for
CBOR, but want to keep the normal Float value for as_json in case that
is used directly (to avoid surprising the user).
If trying to import from IPFS, fallback to gateway
Run all tests on CI
First pass at import resolution
Tests are long for good reasons
Alpha normalization

Internal flag to disable for acceptance tests from the standard (which
assume beta-only normalization in some cases).  Otherwise, just always
alpha normalize as we go.
Update to latest binary format
Fix binary tests
Migrate to dhall-langv6.0.0
Pass most compliance tests

No import or multiline string support yet