Yes, the language there is Zephyr ASDL [1]. I actually changed this:
Dict(expr* keys, expr* values)
to
Dict(List[expr] keys, List[expr] values)
in our fork for https://oilshell.org/ , and it made a lot more sense to contributors.
It's funny how "sticky" syntax is -- two contributors ALSO read * as "pointer" ! So I changed it to be consistent with MyPy syntax earlier this year, and now I think I should have done that a long time ago.
(It would also make sense to change it to keys: List[expr], as that's the Python 3 syntax for types)
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The funny thing is that while the web page says "Abstract Grammar", I would not call Zephyr ASDL a grammar.
Python has a separate Grammar/Grammar file, that is distinct from this file Python/Python.asdl.
A grammar describes a set of strings, and that's not what ASDL does.
It describes the data structure that the valid strings get transformed to after parsing, and there is not a 1:1 correspondence (e.g. due to the difference between a CST and AST, and other post-parsing validation).
(Pretty sure "ungrammar" from rust-analyzer is nodding at this -- https://rust-analyzer.github.io//blog/2020/10/24/introducing... -- it's "ASDL for concrete syntax trees", i.e. it's not a grammar because it doesn't describe strings; it describes trees)
