bpo-35975: Support parsing earlier minor versions of Python 3 (GH-12086)
This adds a `feature_version` flag to `ast.parse()` (documented) and `compile()` (hidden) that allow tweaking the parser to support older versions of the grammar. In particular if `feature_version` is 5 or 6, the hacks for the `async` and `await` keyword from PEP 492 are reinstated. (For 7 or higher, these are unconditionally treated as keywords, but they are still special tokens rather than `NAME` tokens that the parser driver recognizes.)
https://bugs.python.org/issue35975
diff --git a/Parser/parsetok.c b/Parser/parsetok.c
index 7a6c886..ba33a9a 100644
--- a/Parser/parsetok.c
+++ b/Parser/parsetok.c
@@ -101,6 +101,8 @@
Py_INCREF(err_ret->filename);
tok->filename = err_ret->filename;
+ if (*flags & PyPARSE_ASYNC_HACKS)
+ tok->async_hacks = 1;
return parsetok(tok, g, start, err_ret, flags);
}