Use annotated for array (#4679)

* use Annotated for std::array docstring

* add tests

* fix test

* style: pre-commit fixes

* fix valarray annotation

* style: pre-commit fixes

* refix test

* add FixedSize

* style: pre-commit fixes

* Update test_stl.py

* style: pre-commit fixes

---------

Co-authored-by: Taiju Yamada <taiju.yamada@mujin.co.jp>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: 3 people

include/pybind11/stl.h

@@ -273,11 +273,11 @@ struct array_caster {
     }
 
     PYBIND11_TYPE_CASTER(ArrayType,
-                         const_name("List[") + value_conv::name
+                         const_name<Resizable>(const_name(""), const_name("Annotated["))
+                             + const_name("List[") + value_conv::name + const_name("]")
                              + const_name<Resizable>(const_name(""),
-                                                     const_name("[") + const_name<Size>()
-                                                         + const_name("]"))
-                             + const_name("]"));
+                                                     const_name(", FixedSize(")
+                                                         + const_name<Size>() + const_name(")]")));
 };
 
 template <typename Type, size_t Size>

tests/test_stl.py

@@ -39,8 +39,11 @@ def test_array(doc):
     assert m.load_array(lst)
     assert m.load_array(tuple(lst))
 
-    assert doc(m.cast_array) == "cast_array() -> List[int[2]]"
-    assert doc(m.load_array) == "load_array(arg0: List[int[2]]) -> bool"
+    assert doc(m.cast_array) == "cast_array() -> Annotated[List[int], FixedSize(2)]"
+    assert (
+        doc(m.load_array)
+        == "load_array(arg0: Annotated[List[int], FixedSize(2)]) -> bool"
+    )
 
 
 def test_valarray(doc):