Couldn't find the language specification anywhere, it basically the Nix source? The repo's README refers to the Nix manual, but it seems incomplete. For example
http-get
flutter-opacity
instascan
ledger-tables
webargs
xbim
fcoalesce
anymatch
cython
jogl
flops
visual-studio-2017
pyarrow
ruby-build
linux-namespaces
ngx-charts
javax.imageio
mdxjs
laravel-authorization
autoloader
atom-runner
multiple-join-rows
vavr
erb
angular-package-format
nginx-log
fetchxml
fibonacci
angular-strap
icu4c