gh-146495: Improve SyntaxError message for && and || operators (#150906)

Author: Aniketsy

Grammar/python.gram

@@ -819,6 +819,7 @@ is_bitwise_or[CmpopExprPair*]: 'is' a=bitwise_or { _PyPegen_cmpop_expr_pair(p, I
 
 bitwise_or[expr_ty]:
     | a=bitwise_or '|' b=bitwise_xor { _PyAST_BinOp(a, BitOr, b, EXTRA) }
+    | invalid_bitwise_or
     | bitwise_xor
 
 bitwise_xor[expr_ty]:
@@ -827,6 +828,7 @@ bitwise_xor[expr_ty]:
 
 bitwise_and[expr_ty]:
     | a=bitwise_and '&' b=shift_expr { _PyAST_BinOp(a, BitAnd, b, EXTRA) }
+    | invalid_bitwise_and
     | shift_expr
 
 shift_expr[expr_ty]:
@@ -1638,3 +1640,17 @@ invalid_type_params:
         RAISE_SYNTAX_ERROR_STARTING_FROM(
             token,
             "Type parameter list cannot be empty")}
+
+invalid_bitwise_and:
+    | a=bitwise_and b='&' c='&' {
+        _PyPegen_tokens_are_adjacent(b, c)
+        ? RAISE_SYNTAX_ERROR_KNOWN_RANGE(b, c, "invalid syntax.  Maybe you meant 'and' or '&' instead of '&&'?")
+        : NULL
+    }
+
+invalid_bitwise_or:
+    | a=bitwise_or b='|' c='|' {
+        _PyPegen_tokens_are_adjacent(b, c)
+        ? RAISE_SYNTAX_ERROR_KNOWN_RANGE(b, c, "invalid syntax.  Maybe you meant 'or' or '|' instead of '||'?")
+        : NULL
+    }

Lib/test/test_syntax.py

@@ -3505,6 +3505,50 @@ def test_ifexp_body_stmt_else_stmt(self):
         ]:
             self._check_error(f"x = {lhs_stmt} if 1 else {rhs_stmt}", msg)
 
+    def test_double_ampersand(self):
+        self._check_error(
+            "a && b",
+            r"Maybe you meant 'and' or '&' instead of '&&'\?",
+            lineno=1,
+            end_lineno=1,
+            offset=3,
+            end_offset=5,
+        )
+        self._check_error(
+            "a & & b",
+            "invalid syntax",
+            lineno=1,
+            end_lineno=1,
+            offset=5,
+            end_offset=6,
+        )
+        self._check_error(
+            "(a &\n    & b)",
+            "invalid syntax",
+            lineno=2,
+            end_lineno=2,
+            offset=5,
+            end_offset=6,
+        )
+
+    def test_double_pipe(self):
+        self._check_error(
+            "a || b",
+            r"Maybe you meant 'or' or '|' instead of '||'\?",
+            lineno=1,
+            end_lineno=1,
+            offset=3,
+            end_offset=5,
+        )
+        self._check_error(
+            "a | | b",
+            "invalid syntax",
+            lineno=1,
+            end_lineno=1,
+            offset=5,
+            end_offset=6,
+        )
+
 
 class LazyImportRestrictionTestCase(SyntaxErrorTestCase):
     """Test syntax restrictions for lazy imports."""

Misc/NEWS.d/next/Core_and_Builtins/2026-06-04-15-02-35.gh-issue-146495.wWRRvx.rst

@@ -0,0 +1 @@
+Improve :exc:`SyntaxError` message for ``&&`` and ``||`` operators, suggesting ``and``/``&`` and ``or``/``|`` respectively.