bpo-24612: Improve syntax error for 'not' after an operator

pablogsal · pablogsal · commit 1660f6fe9ae9 · 2021-09-05T14:47:35.000+01:00
diff --git a/Grammar/python.gram b/Grammar/python.gram
@@ -722,6 +722,7 @@ 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
@@ -1249,3 +1250,6 @@ invalid_kvpair:
         RAISE_ERROR_KNOWN_LOCATION(p, PyExc_SyntaxError, a->lineno, a->end_col_offset - 1, a->end_lineno, -1, "':' expected after dictionary key") }
     | expression ':' a='*' bitwise_or { RAISE_SYNTAX_ERROR_STARTING_FROM(a, "cannot use a starred expression in a dictionary value") }
     | expression a=':' {RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "expression expected after dictionary key and ':'") }
+
+invalid_arithmetic:
+    | sum ('+'|'-'|'*'|'/'|'~'|'%'|'//'|'@') a='not' b=inversion { RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b, "'not' after an operator must be parenthesized") }
diff --git a/Lib/test/test_syntax.py b/Lib/test/test_syntax.py
@@ -1194,6 +1194,29 @@
 Traceback (most recent call last):
 SyntaxError: only single target (not list) can be annotated
 
+# 'not' after operators:
+
+>>> 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
+
+>>> 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):
+SyntaxError: invalid syntax
+
+>>> not 1 +
+Traceback (most recent call last):
+SyntaxError: invalid syntax
+
 Corner-cases that used to fail to raise the correct error:
 
     >>> def f(*, x=lambda __debug__:0): pass
diff --git a/Misc/NEWS.d/next/Core and Builtins/2021-09-04-22-33-01.bpo-24612.SsTuUX.rst b/Misc/NEWS.d/next/Core and Builtins/2021-09-04-22-33-01.bpo-24612.SsTuUX.rst
@@ -0,0 +1,2 @@
+Improve the :exc:`SyntaxError` that happens when 'not' appears after an
+operator. Patch by Pablo Galindo
diff --git a/Parser/parser.c b/Parser/parser.c

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	+Improve the :exc:`SyntaxError` that happens when 'not' appears after an
	`2`	`+operator. Patch by Pablo Galindo`