@@ -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
@@ -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]:
@@ -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) }
 
@@ -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):
 
@@ -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``.
Original file line number	Diff line number	Diff line change
@@ -0,0 +1,3 @@
	1	+ Improve syntax error messages for misplaced ``not`` after an operator
	2	+ in contexts where a generic "invalid syntax" error was previously reported,
	3	+ such as ``1 << 2 + not x`` and ``1 * + not x``.