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gh-153171: Produce specialized syntax errors for 'not' after an operator in more positions #153175

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Merged
serhiy-storchaka merged 1 commit into from
Jul 6, 2026
+64 −45
Merged

gh-153171: Produce specialized syntax errors for 'not' after an operator in more positions #153175

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4 changes: 2 additions & 2 deletions Grammar/python.gram
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Original file line number Diff line number Diff line change
Expand Up @@ -835,7 +835,6 @@ bitwise_and[expr_ty]:
shift_expr[expr_ty]:
| a=shift_expr '<<' b=sum { _PyAST_BinOp(a, LShift, b, EXTRA) }
| a=shift_expr '>>' b=sum { _PyAST_BinOp(a, RShift, b, EXTRA) }
| invalid_arithmetic
| sum

# Arithmetic operators
Expand All @@ -844,6 +843,7 @@ shift_expr[expr_ty]:
sum[expr_ty]:
| a=sum '+' b=term { _PyAST_BinOp(a, Add, b, EXTRA) }
| a=sum '-' b=term { _PyAST_BinOp(a, Sub, b, EXTRA) }
| invalid_arithmetic
| term

term[expr_ty]:
Expand All @@ -852,14 +852,14 @@ term[expr_ty]:
| a=term '//' b=factor { _PyAST_BinOp(a, FloorDiv, b, EXTRA) }
| a=term '%' b=factor { _PyAST_BinOp(a, Mod, b, EXTRA) }
| a=term '@' b=factor { CHECK_VERSION(expr_ty, 5, "The '@' operator is", _PyAST_BinOp(a, MatMult, b, EXTRA)) }
| invalid_factor
| factor

factor[expr_ty] (memo):
| '+' a=factor { _PyAST_UnaryOp(UAdd, a, EXTRA) }
| '-' a=factor { _PyAST_UnaryOp(USub, a, EXTRA) }
| '~' a=factor { _PyAST_UnaryOp(Invert, a, EXTRA) }
| power
| invalid_factor

power[expr_ty]:
| a=await_primary '**' b=factor { _PyAST_BinOp(a, Pow, b, EXTRA) }
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16 changes: 16 additions & 0 deletions Lib/test/test_syntax.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2268,6 +2268,22 @@
Traceback (most recent call last):
SyntaxError: 'not' after an operator must be parenthesized
>>> 1 << 2 + not 3
Traceback (most recent call last):
SyntaxError: 'not' after an operator must be parenthesized
>>> 1 >> 2 * not 3
Traceback (most recent call last):
SyntaxError: 'not' after an operator must be parenthesized
>>> 3 * + not 3
Traceback (most recent call last):
SyntaxError: 'not' after an operator must be parenthesized
>>> 3 ** - not 3
Traceback (most recent call last):
SyntaxError: 'not' after an operator must be parenthesized
# Check that we don't introduce misleading errors
>>> not 1 */ 2
Traceback (most recent call last):
Expand Down
3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2026-07-06-18-00-00.gh-issue-153171.errloc1.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Improve syntax error messages for misplaced ``not`` after an operator
in contexts where a generic "invalid syntax" error was previously reported,
such as ``1 << 2 + not x`` and ``1 * + not x``.
86 changes: 43 additions & 43 deletions Parser/parser.c
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