8000 gh-123562: Improve `SyntaxError` message for `case ... as a.b` by sobolevn · Pull Request #123563 · python/cpython · GitHub
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gh-123562: Improve SyntaxError message for case ... as a.b #123563

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Merged
merged 3 commits into from
Sep 2, 2024
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gh-123562: Improve SyntaxError message for case ... as a.b #123563

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c0cf895
gh-123562: Improve `SyntaxError` message for `case ... as a.b`
sobolevn Sep 1, 2024
0ec069c
One more test
sobolevn Sep 1, 2024
bd7e806
Address review
sobolevn Sep 2, 2024
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4 changes: 3 additions & 1 deletion Grammar/python.gram
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Original file line number Diff line number Diff line change
Expand Up @@ -1375,7 +1375,9 @@ invalid_case_block:
RAISE_INDENTATION_ERROR("expected an indented block after 'case' statement on line %d", a->lineno) }
invalid_as_pattern:
| or_pattern 'as' a="_" { RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "cannot use '_' as a target") }
| or_pattern 'as' !NAME a=expression { RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "invalid pattern target") }
| or_pattern 'as' a=expression {
RAISE_SYNTAX_ERROR_KNOWN_LOCATION(
a, "cannot use %s as pattern target", _PyPegen_get_expr_name(a)) }
invalid_class_pattern:
| name_or_attr '(' a=invalid_ 10000 class_argument_pattern { RAISE_SYNTAX_ERROR_KNOWN_RANGE(
PyPegen_first_item(a, pattern_ty),
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7 changes: 7 additions & 0 deletions Lib/test/test_patma.py
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Expand Up @@ -3015,6 +3015,13 @@ def test_multiple_assignments_to_name_in_pattern_5(self):
pass
""")

def test_multiple_assignments_to_name_in_pattern_6(self):
self.assert_syntax_error("""
match ...:
case a as a + 1: # NAME and expression with no ()
pass
""")

def test_multiple_starred_names_in_sequence_pattern_0(self):
self.assert_syntax_error("""
match ...:
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42 changes: 41 additions & 1 deletion Lib/test/test_syntax.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1932,7 +1932,31 @@
... case 42 as 1+2+4:
... ...
Traceback (most recent call last):
SyntaxError: invalid pattern target
SyntaxError: cannot use expression as pattern target

>>> match ...:
... case 42 as a.b:
... ...
Traceback (most recent call last):
SyntaxError: cannot use attribute as pattern target

>>> match ...:
... case 42 as (a, b):
... ...
Traceback (most recent call last):
SyntaxError: cannot use tuple as pattern target

>>> match ...:
... case 42 as (a + 1):
... ...
Traceback (most recent call last):
SyntaxError: cannot use expression as pattern target

>>> match ...:
... case (32 as x) | (42 as a()):
... ...
Traceback (most recent call last):
SyntaxError: cannot use function call as pattern target

>>> match ...:
... case Foo(z=1, y=2, x):
Expand Down Expand Up @@ -2817,6 +2841,22 @@ def test_except_stmt_invalid_as_expr(self):
end_offset=22 + len("obj.attr"),
)

def test_match_stmt_invalid_as_expr(self):
self._check_error(
textwrap.dedent(
"""
match 1:
case x as obj.attr:
...
"""
),
errtext="cannot use attribute as pattern target",
lineno=3,
end_lineno=3,
offset=15,
end_offset=15 + len("obj.attr"),
)


def load_tests(loader, tests, pattern):
tests.addTest(doctest.DocTestSuite())
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2024-09-01-12-08-39.gh-issue-123562.aJPKVu.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Improve :exc:`SyntaxError` message for using ``case ... as ...`` with not a
name.
14 changes: 6 additions & 8 deletions Parser/parser.c
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