From 21f52eb0c7778058ffe0c73317b1c1d5cecf7522 Mon Sep 17 00:00:00 2001
From: Tim Ohliger <ohliger.tim@gmail.com>
Date: Fri, 10 Jan 2025 11:59:37 +0100
Subject: [PATCH] Simplified special character check

---
 include/pybind11/pybind11.h | 7 ++++---
 tests/test_pytypes.cpp      | 2 +-
 tests/test_pytypes.py       | 2 +-
 3 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index 5e277d5a1a..655bec3986 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -445,6 +445,9 @@ class cpp_function : public function {
         // signature. Using `@^`/`@$` we can force types to be arg/return types while `@!` pops
         // back to the previous state.
         std::stack<bool> is_return_value({false});
+        // The following characters have special meaning in the signature parsing. Literals
+        // containing these are escaped with `!`.
+        std::string special_chars("!@%{}-");
         for (const auto *pc = text; *pc != '\0'; ++pc) {
             const auto c = *pc;
 
@@ -498,9 +501,7 @@ class cpp_function : public function {
                 } else {
                     signature += detail::quote_cpp_type_name(detail::clean_type_id(t->name()));
                 }
-            } else if (c == '!'
-                       && (*(pc + 1) == '!' || *(pc + 1) == '@' || *(pc + 1) == '%'
-                           || *(pc + 1) == '{' || *(pc + 1) == '}' || *(pc + 1) == '-')) {
+            } else if (c == '!' && special_chars.find(*(pc + 1)) != std::string::npos) {
                 // typing::Literal escapes special characters with !
                 signature += *++pc;
             } else if (c == '@') {
diff --git a/tests/test_pytypes.cpp b/tests/test_pytypes.cpp
index 209513db9d..5160e9f408 100644
--- a/tests/test_pytypes.cpp
+++ b/tests/test_pytypes.cpp
@@ -971,7 +971,7 @@ TEST_SUBMODULE(pytypes, m) {
         .value("BLUE", literals::Color::BLUE);
 
     m.def("annotate_literal", [](literals::LiteralFoo &o) -> py::object { return o; });
-    // Literal with `@`, `%`, `{`, and `}`
+    // Literal with `@`, `%`, `{`, `}`, and `->`
     m.def("identity_literal_exclamation", [](const py::typing::Literal<"\"!\""> &x) { return x; });
     m.def("identity_literal_at", [](const py::typing::Literal<"\"@\""> &x) { return x; });
     m.def("identity_literal_percent", [](const py::typing::Literal<"\"%\""> &x) { return x; });
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index 9edc6ea5ec..469137cc3c 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -1044,7 +1044,7 @@ def test_literal(doc):
         doc(m.annotate_literal)
         == 'annotate_literal(arg0: Literal[26, 0x1A, "hello world", b"hello world", u"hello world", True, Color.RED, None]) -> object'
     )
-    # The characters !, @, %, and {} are used in the signature parser as special characters, but Literal should escape those for the parser to work.
+    # The characters !, @, %, {, } and -> are used in the signature parser as special characters, but Literal should escape those for the parser to work.
     assert (
         doc(m.identity_literal_exclamation)
         == 'identity_literal_exclamation(arg0: Literal["!"]) -> Literal["!"]'