add helper function, update tests

Author: Aniketsy

Grammar/python.gram

@@ -801,18 +801,15 @@ compare_op_bitwise_or_pair[CmpopExprPair*]:
     | in_bitwise_or
     | isnot_bitwise_or
     | is_bitwise_or
-    | invalid_diamond_op
     | invalid_eqeqeq
 
-invalid_diamond_op:
-    | a='<' b='>' {
-        (p->flags & PyPARSE_BARRY_AS_BDFL)
-        ? RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b, "invalid syntax.  Maybe you meant '<>' instead of '< >'?")
-        : RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b, "invalid syntax.  Maybe you meant '!=' instead of '<>'?")
-    }
 eq_bitwise_or[CmpopExprPair*]: '==' a=bitwise_or { _PyPegen_cmpop_expr_pair(p, Eq, a) }
 invalid_eqeqeq:
-    | a='==' b='=' { RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b, "invalid syntax.  Maybe you meant 'is' instead of '==='?") }
+    | a='==' b='=' {
+        _PyPegen_tokens_are_adjacent(a, b)
+        ? RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b, "invalid syntax.  Maybe you meant 'is' instead of '==='?")
+        : NULL
+    }
 noteq_bitwise_or[CmpopExprPair*]:
     | (tok='!=' { _PyPegen_check_barry_as_flufl(p, tok) ? NULL : tok}) a=bitwise_or {_PyPegen_cmpop_expr_pair(p, NotEq, a) }
 lte_bitwise_or[CmpopExprPair*]: '<=' a=bitwise_or { _PyPegen_cmpop_expr_pair(p, LtE, a) }
@@ -1323,9 +1320,21 @@ invalid_assignment:
             "'%s' is an illegal expression for augmented assignment",
             _PyPegen_get_expr_name(a)
         )}
-    | star_expressions a='=' b='<' { RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b, "invalid syntax.  Maybe you meant '<=' instead of '=<'?") }
-    | star_expressions a='=' b='>' { RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b, "invalid syntax.  Maybe you meant '>=' instead of '=>'?") }
-    | star_expressions a='=' b='!' { RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b, "invalid syntax.  Maybe you meant '!=' instead of '=!'?") }
+    | star_expressions a='=' b='<' {
+        _PyPegen_tokens_are_adjacent(a, b)
+        ? RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b, "invalid syntax.  Maybe you meant '<=' instead of '=<'?")
+        : NULL
+    }
+    | star_expressions a='=' b='>' {
+        _PyPegen_tokens_are_adjacent(a, b)
+        ? RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b, "invalid syntax.  Maybe you meant '>=' instead of '=>'?")
+        : NULL
+    }
+    | star_expressions a='=' b='!' {
+        _PyPegen_tokens_are_adjacent(a, b)
+        ? RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b, "invalid syntax.  Maybe you meant '!=' instead of '=!'?")
+        : NULL
+    }
 invalid_ann_assign_target[expr_ty]:
     | list
     | tuple

Lib/test/test_syntax.py

@@ -3514,17 +3514,22 @@ def test_diamond_operator(self):
             offset=2,
             end_offset=4,
         )
-
-    def test_diamond_operator_barry_as_flufl(self):
         self._check_error(
-            "from __future__ import barry_as_FLUFL\n1 < > 2",
-            "Maybe you meant '<>' instead of '< >'",
-            lineno=2,
-            end_lineno=2,
-            offset=3,
+            "1 < > 2",
+            "invalid syntax",
+            lineno=1,
+            end_lineno=1,
+            offset=5,
             end_offset=6,
         )
 
+    def test_diamond_operator_barry_as_flufl(self):
+        # Under barry_as_FLUFL, '<>' is the valid "not equal" operator
+        compile(
+            "from __future__ import barry_as_FLUFL\n1<>2",
+            "<test>", "exec",
+        )
+
     def test_triple_equal(self):
         self._check_error(
             "a === b",
@@ -3534,6 +3539,14 @@ def test_triple_equal(self):
             offset=3,
             end_offset=6,
         )
+        self._check_error(
+            "a == = b",
+            "invalid syntax",
+            lineno=1,
+            end_lineno=1,
+            offset=6,
+            end_offset=7,
+        )
 
     def test_eq_lt_typo(self):
         self._check_error(

Misc/NEWS.d/next/Core_and_Builtins/2026-06-12-03-41-39.gh-issue-151303.mzlJxi.rst

@@ -1 +1 @@
-Improve :exc:`SyntaxError` message for ``===``, ``=<``, ``=>``, ``=!``, and ``<>`` operators, suggesting ``==``, ``<=``, ``>=``, ``!=``, and ``!=`` respectively.
+Improve :exc:`SyntaxError` messages for common operator typos coming from other languages: ``=<``, ``=>``, and ``=!`` now suggest ``<=``, ``>=``, and ``!=`` respectively, ``===`` suggests ``is``, and ``<>`` shows a tailored message suggesting ``!=``.