added an API to enable/disable implicit cast failure warnings

Author: wjakob

Diff for: include/nanobind/nb_lib.h

@@ -413,6 +413,7 @@ NB_CORE void decref_checked(PyObject *o) noexcept;
 // ========================================================================
 
 NB_CORE void set_leak_warnings(bool value) noexcept;
+NB_CORE void set_implicit_cast_warnings(bool value) noexcept;
 
 // ========================================================================
 

Diff for: include/nanobind/nb_misc.h

@@ -58,4 +58,8 @@ inline void set_leak_warnings(bool value) noexcept {
     detail::set_leak_warnings(value);
 }
 
+inline void set_implicit_cast_warnings(bool value) noexcept {
+    detail::set_implicit_cast_warnings(value);
+}
+
 NAMESPACE_END(NB_NAMESPACE)

Diff for: src/common.cpp

@@ -931,6 +931,10 @@ void set_leak_warnings(bool value) noexcept {
     internals_get().print_leak_warnings = value;
 }
 
+void set_implicit_cast_warnings(bool value) noexcept {
+    internals_get().print_implicit_cast_warnings = value;
+}
+
 // ========================================================================
 
 void slice_compute(PyObject *slice, Py_ssize_t size, Py_ssize_t &start,

Diff for: src/nb_internals.h

@@ -203,8 +203,11 @@ struct nb_internals {
     /// Registered C++ -> Python exception translators
     std::vector<std::pair<exception_translator, void *>> exception_translators;
 
-    /// Boolean specifying whether to print leak warnings on exit
-    bool print_leak_warnings{true};
+    /// Should nanobind print leak warnings on exit?
+    bool print_leak_warnings = true;
+
+    /// Should nanobind print warnings after implicit cast failures?
+    bool print_implicit_cast_warnings = true;
 };
 
 struct current_method {

Diff for: src/nb_type.cpp

@@ -690,11 +690,13 @@ static NB_NOINLINE bool nb_type_get_implicit(PyObject *src,
     } else {
         PyErr_Clear();
 
-        PyObject *name = nb_inst_name(src);
-        PyErr_WarnFormat(PyExc_RuntimeWarning, 1,
-                         "nanobind: implicit conversion from type '%U' "
-                         "to type '%s' failed!", name, dst_type->name);
-        Py_DECREF(name);
+        if (internals.print_implicit_cast_warnings) {
+            PyObject *name = nb_inst_name(src);
+            PyErr_WarnFormat(PyExc_RuntimeWarning, 1,
+                             "nanobind: implicit conversion from type '%U' "
+                             "to type '%s' failed!", name, dst_type->name);
+            Py_DECREF(name);
+        }
 
         return false;
     }