minor tweaks to nb::cast<T> interface

wjakob · Apr 11, 2023 · 9ae3205 · 9ae3205
1 parent b0bd2ba
commit 9ae3205
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Showing 3 changed files with 29 additions and 14 deletions.
diff --git a/include/nanobind/nb_cast.h b/include/nanobind/nb_cast.h
@@ -338,27 +338,21 @@ T cast(const detail::api<Derived> &value, bool convert = true) {
     if constexpr (std::is_same_v<T, void>) {
         return;
     } else {
-        using Ti     = detail::intrinsic_t<T>;
-        using Caster = detail::make_caster<Ti>;
+        using Caster = detail::make_caster<T>;
+        using Output = typename Caster::template Cast<T>;
+
+        static_assert(
+            !(std::is_reference_v<T> || std::is_pointer_v<T>) || Caster::IsClass ||
+            std::is_same_v<const char *, T>,
+            "nanobind::cast(): cannot return a reference to a temporary.");
 
         Caster caster;
         if (!caster.from_python(value.derived().ptr(),
                                 convert ? (uint8_t) detail::cast_flags::convert
                                         : (uint8_t) 0, nullptr))
             detail::raise_cast_error();
 
-        if constexpr (std::is_same_v<T, const char *>) {
-            return caster.operator const char *();
-        } else {
-            static_assert(
-                !(std::is_reference_v<T> || std::is_pointer_v<T>) || Caster::IsClass,
-                "nanobind::cast(): cannot return a reference to a temporary.");
-
-            if constexpr (detail::is_pointer_v<T>)
-                return caster.operator Ti*();
-            else
-                return caster.operator Ti&();
-        }
+        return caster.operator Output();
     }
 }
 

diff --git a/tests/test_functions.cpp b/tests/test_functions.cpp
@@ -212,4 +212,12 @@ NB_MODULE(test_functions_ext, m) {
 
         return nb::cpp_function(callback);
     });
+
+    m.def("test_cast_char", [](nb::handle h) {
+        return nb::cast<char>(h);
+    });
+
+    m.def("test_cast_str", [](nb::handle h) {
+        return nb::cast<const char *>(h);
+    });
 }
diff --git a/tests/test_functions.py b/tests/test_functions.py
@@ -307,3 +307,16 @@ def test34_module_docstring():
 def test35_return_capture():
     x = t.test_35()
     assert x() == 'Test Foo'
+
+def test36_test_char():
+    assert t.test_cast_char('c') == 'c'
+    with pytest.raises(TypeError):
+        assert t.test_cast_char('abc')
+    with pytest.raises(RuntimeError):
+        assert t.test_cast_char(123)
+
+def test37_test_str():
+    assert t.test_cast_str('c') == 'c'
+    assert t.test_cast_str('abc') == 'abc'
+    with pytest.raises(RuntimeError):
+        assert t.test_cast_str(123)