From 2be85c604167e4097edab9cd7b4215e85f1ae8d1 Mon Sep 17 00:00:00 2001
From: Michael Carlstrom <rmc@carlstrom.com>
Date: Tue, 25 Jun 2024 22:53:15 -0400
Subject: [PATCH] feat(types): adds support for TypeGuard and TypeIs (#5194)

* Adds support for TypeGuard and TypeIs

* style: pre-commit fixes

---------

Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
---
 include/pybind11/typing.h | 22 ++++++++++++++++++++++
 tests/test_pytypes.cpp    |  7 +++++++
 tests/test_pytypes.py     | 11 +++++++++++
 3 files changed, 40 insertions(+)

diff --git a/include/pybind11/typing.h b/include/pybind11/typing.h
index 55f1f949d..cf70b739e 100644
--- a/include/pybind11/typing.h
+++ b/include/pybind11/typing.h
@@ -80,6 +80,16 @@ class Optional : public object {
     using object::object;
 };
 
+template <typename T>
+class TypeGuard : public bool_ {
+    using bool_::bool_;
+};
+
+template <typename T>
+class TypeIs : public bool_ {
+    using bool_::bool_;
+};
+
 class NoReturn : public none {
     using none::none;
 };
@@ -87,6 +97,7 @@ class NoReturn : public none {
 class Never : public none {
     using none::none;
 };
+
 #if defined(__cpp_nontype_template_parameter_class)
 template <size_t N>
 struct StringLiteral {
@@ -183,6 +194,16 @@ struct handle_type_name<typing::Optional<T>> {
     static constexpr auto name = const_name("Optional[") + make_caster<T>::name + const_name("]");
 };
 
+template <typename T>
+struct handle_type_name<typing::TypeGuard<T>> {
+    static constexpr auto name = const_name("TypeGuard[") + make_caster<T>::name + const_name("]");
+};
+
+template <typename T>
+struct handle_type_name<typing::TypeIs<T>> {
+    static constexpr auto name = const_name("TypeIs[") + make_caster<T>::name + const_name("]");
+};
+
 template <>
 struct handle_type_name<typing::NoReturn> {
     static constexpr auto name = const_name("NoReturn");
@@ -192,6 +213,7 @@ template <>
 struct handle_type_name<typing::Never> {
     static constexpr auto name = const_name("Never");
 };
+
 #if defined(__cpp_nontype_template_parameter_class)
 template <typing::StringLiteral... Literals>
 struct handle_type_name<typing::Literal<Literals...>> {
diff --git a/tests/test_pytypes.cpp b/tests/test_pytypes.cpp
index ce6b93326..6b347894b 100644
--- a/tests/test_pytypes.cpp
+++ b/tests/test_pytypes.cpp
@@ -892,8 +892,15 @@ TEST_SUBMODULE(pytypes, m) {
               return list;
           });
 
+    m.def("annotate_type_guard", [](py::object &o) -> py::typing::TypeGuard<py::str> {
+        return py::isinstance<py::str>(o);
+    });
+    m.def("annotate_type_is",
+          [](py::object &o) -> py::typing::TypeIs<py::str> { return py::isinstance<py::str>(o); });
+
     m.def("annotate_no_return", []() -> py::typing::NoReturn { throw 0; });
     m.def("annotate_never", []() -> py::typing::Never { throw 0; });
+
     m.def("annotate_optional_to_object",
           [](py::typing::Optional<int> &o) -> py::object { return o; });
 
diff --git a/tests/test_pytypes.py b/tests/test_pytypes.py
index 923cebaf5..92a3a36bf 100644
--- a/tests/test_pytypes.py
+++ b/tests/test_pytypes.py
@@ -991,6 +991,17 @@ def test_optional_annotations(doc):
     )
 
 
+def test_type_guard_annotations(doc):
+    assert (
+        doc(m.annotate_type_guard)
+        == "annotate_type_guard(arg0: object) -> TypeGuard[str]"
+    )
+
+
+def test_type_is_annotations(doc):
+    assert doc(m.annotate_type_is) == "annotate_type_is(arg0: object) -> TypeIs[str]"
+
+
 def test_no_return_annotation(doc):
     assert doc(m.annotate_no_return) == "annotate_no_return() -> NoReturn"