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[3.10] bpo-44456: Improve the syntax error when mixing keyword and positional patterns (GH-26793) #26900

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Merged
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Jun 24, 2021
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[3.10] bpo-44456: Improve the syntax error when mixing keyword and positional patterns (GH-26793) #26900

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8 changes: 8 additions & 0 deletions Grammar/python.gram
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Original file line number Diff line number Diff line change
Expand Up @@ -380,6 +380,7 @@ class_pattern[pattern_ty]:
CHECK(asdl_expr_seq*, _PyPegen_get_pattern_keys(p, keywords)))),
CHECK(asdl_pattern_seq*, _PyPegen_get_patterns(p, keywords)),
EXTRA) }
| invalid_class_pattern
positional_patterns[asdl_pattern_seq*]:
| args[asdl_pattern_seq*]=','.pattern+ { args }
keyword_patterns[asdl_seq*]:
Expand Down Expand Up @@ -978,6 +979,13 @@ invalid_case_block:
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") }
invalid_class_pattern:
| name_or_attr '(' a=invalid_class_argument_pattern { RAISE_SYNTAX_ERROR_KNOWN_RANGE(
PyPegen_first_item(a, pattern_ty),
PyPegen_last_item(a, pattern_ty),
"positional patterns follow keyword patterns") }
invalid_class_argument_pattern[asdl_pattern_seq*]:
| [positional_patterns ','] keyword_patterns ',' a=positional_patterns { a }
invalid_if_stmt:
| 'if' named_expression NEWLINE { RAISE_SYNTAX_ERROR("expected ':'") }
| a='if' a=named_expression ':' NEWLINE !INDENT {
Expand Down
24 changes: 24 additions & 0 deletions Lib/test/test_syntax.py
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Expand Up @@ -1240,6 +1240,30 @@
... ...
Traceback (most recent call last):
SyntaxError: invalid pattern target

>>> match ...:
... case Foo(z=1, y=2, x):
... ...
Traceback (most recent call last):
SyntaxError: positional patterns follow keyword patterns

>>> match ...:
... case Foo(a, z=1, y=2, x):
... ...
Traceback (most recent call last):
SyntaxError: positional patterns follow keyword patterns

>>> match ...:
... case Foo(z=1, x, y=2):
... ...
Traceback (most recent call last):
SyntaxError: positional patterns follow keyword patterns

>>> match ...:
... case C(a=b, c, d=e, f, g=h, i, j=k, ...):
... ...
Traceback (most recent call last):
SyntaxError: positional patterns follow keyword patterns
"""

import re
Expand Down
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2021-06-18-22-08-25.bpo-44456.L0Rhko.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Improve the syntax error when mixing positional and keyword patterns. Patch
by Pablo Galindo.
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