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bpo-43224: Implement PEP 646 grammar changes #31018

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Merged
merged 17 commits into from
Mar 26, 2022
+3,056 −2,128
Merged

bpo-43224: Implement PEP 646 grammar changes #31018

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7ecb7ba
bpo-43224: Implement PEP 646 grammar changes
mrahtz Jan 30, 2022
c0531ec
Add tests for del
mrahtz Jan 30, 2022
479c175
Tweak news to better fit in with other PRs
mrahtz Jan 30, 2022
091ceeb
Move error cases into test_syntax
mrahtz Feb 13, 2022
f1c9c77
Add an extra failure test
mrahtz Feb 14, 2022
c8d2534
Add more tests combining slicing with starring
mrahtz Mar 17, 2022
5df1e97
Fix ast representation of slices combined with starring
mrahtz Mar 17, 2022
677a326
Fix broken test in test_unparse
mrahtz Mar 17, 2022
1543785
Add a check_src_roundtrip test for "a[1:2, *a]"
mrahtz Mar 17, 2022
e1ab6ea
fix whitespace (make patchcheck)
JelleZijlstra Mar 23, 2022
18e7fa7
Merge remote-tracking branch 'upstream/main' into pep646-grammar
JelleZijlstra Mar 23, 2022
72dd8b9
Add tests for AST changes
mrahtz Mar 24, 2022
80bb5fa
Fix C unpack
mrahtz Mar 24, 2022
fbfd5b1
Fix typing.get_type_hints on variadic annotation
mrahtz Mar 24, 2022
816098c
Fix typo
mrahtz Mar 24, 2022
8962d26
Remove debug print
mrahtz Mar 25, 2022
973e9cc
Fix potential shadowing in ForwardRef
mrahtz Mar 25, 2022
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Fix typing.get_type_hints on variadic annotation
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@mrahtz
mrahtz committed Mar 24, 2022
commit fbfd5b142ee2bb4f136fabd0b38946b6b42fb02c
21 changes: 20 additions & 1 deletion Lib/test/test_future.py
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Original file line number Diff line number Diff line change
Expand Up @@ -175,7 +175,7 @@ def _exec_future(self, code):
scope = {}
exec(
"from __future__ import annotations\n"
+ code, {}, scope
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I removed this because if both globals and locals are passed to exec, it treats the code as it if were executed in a class definition, which makes the new test I've added harder than it needs to be (we can't access c so easily). Removing this doesn't seem to break any of the rest of the tests, so I hope this is fine?

+ code, scope
)
return scope

Expand Down Expand Up @@ -419,6 +419,25 @@ def foo():
def bar(arg: (yield)): pass
"""))

def test_get_type_hints_on_func_with_variadic_arg(self):
# `typing.get_type_hints` might break on a function with a variadic
# annotation (e.g. `f(*args: *Ts)`) if `from __future__ import
# annotations`, because it could try to evaluate `*Ts` as en expression,
# which on its own isn't value syntax.
namespace = self._exec_future(dedent("""\
class StarredC: pass
class C:
def __iter__(self):
yield StarredC()
c = C()
def f(*args: *c): pass
import typing
hints = typing.get_type_hints(f)
"""))

hints = namespace.pop('hints')
self.assertIsInstance(hints['args'], namespace['StarredC'])


if __name__ == "__main__":
unittest.main()
12 changes: 11 additions & 1 deletion Lib/typing.py
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Original file line number Diff line number Diff line change
Expand Up @@ -734,10 +734,20 @@ class ForwardRef(_Final, _root=True):
def __init__(self, arg, is_argument=True, module=None, *, is_class=False):
if not isinstance(arg, str):
raise TypeError(f"Forward reference must be a string -- got {arg!r}")

# If we do `def f(*args: *Ts)`, then we'll have `arg = '*Ts'`.
# Unfortunately, this isn't a valid expression on its own, so we
# do the unpacking manually.
if arg[0] == '*':
arg_to_compile = f'next(iter({arg[1:]}))'
else:
arg_to_compile = arg
print(f"arg_to_compile: '{arg_to_compile}'")
try:
code = compile(arg, '<string>', 'eval')
code = compile(arg_to_compile, '<string>', 'eval')
except SyntaxError:
raise SyntaxError(f"Forward reference must be an expression -- got {arg!r}")

self.__forward_arg__ = arg
self.__forward_code__ = code
self.__forward_evaluated__ = False
Expand Down