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bpo-45450: Improve syntax error for parenthesized arguments #28906

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Merged
merged 1 commit into from
Nov 20, 2021
Merged

bpo-45450: Improve syntax error for parenthesized arguments #28906

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4 changes: 4 additions & 0 deletions Grammar/python.gram
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Original file line number Diff line number Diff line change
Expand Up @@ -1140,12 +1140,16 @@ invalid_dict_comprehension:
invalid_parameters:
| param_no_default* invalid_parameters_helper a=param_no_default {
RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "non-default argument follows default argument") }
| param_no_default* a='(' param_no_default+ ','? b=')' {
RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b, "Function parameters cannot be parenthesized") }
invalid_parameters_helper: # This is only there to avoid type errors
| a=slash_with_default { _PyPegen_singleton_seq(p, a) }
| param_with_default+
invalid_lambda_parameters:
| lambda_param_no_default* invalid_lambda_parameters_helper a=lambda_param_no_default {
RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "non-default argument follows default argument") }
| lambda_param_no_default* a='(' ','.lambda_param+ ','? b=')' {
RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b, "Lambda expression parameters cannot be parenthesized") }
invalid_lambda_parameters_helper:
| a=lambda_slash_with_default { _PyPegen_singleton_seq(p, a) }
| lambda_param_with_default+
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38 changes: 38 additions & 0 deletions Lib/test/test_syntax.py
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Expand Up @@ -909,6 +909,44 @@
Traceback (most recent call last):
SyntaxError: expected '('

Parenthesized arguments in function definitions

>>> def f(x, (y, z), w):
... pass
Traceback (most recent call last):
SyntaxError: Function parameters cannot be parenthesized

>>> def f((x, y, z, w)):
... pass
Traceback (most recent call last):
SyntaxError: Function parameters cannot be parenthesized

>>> def f(x, (y, z, w)):
... pass
Traceback (most recent call last):
SyntaxError: Function parameters cannot be parenthesized

>>> def f((x, y, z), w):
... pass
Traceback (most recent call last):
SyntaxError: Function parameters cannot be parenthesized

>>> lambda x, (y, z), w: None
Traceback (most recent call last):
SyntaxError: Lambda expression parameters cannot be parenthesized

>>> lambda (x, y, z, w): None
Traceback (most recent call last):
SyntaxError: Lambda expression parameters cannot be parenthesized

>>> lambda x, (y, z, w): None
Traceback (most recent call last):
SyntaxError: Lambda expression parameters cannot be parenthesized

>>> lambda (x, y, z), w: None
Traceback (most recent call last):
SyntaxError: Lambda expression parameters cannot be parenthesized

Custom error messages for try blocks that are not followed by except/finally

>>> try:
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2021-10-12-18-22-44.bpo-45450.d9a-bX.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Improve the syntax error message for parenthesized arguments. Patch by Pablo
Galindo.
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