[mlir:python] Add manual typing annotations to mlir.register_* functions.

This PR adds a manual typing annotations to the `register_operation` and
`register_(type|value)_caster` functions in the main `mlir` module.
Since those functions return the result `nb::cpp_function`, which is of
type `nb::object`, the automatic typing annocations are of the form
`def f() -> object`. This isn't particularly precise and leads to type
checking errors when the functions are used. Manually defining the
annotation with `nb::sig` solves the problem.

Signed-off-by: Ingo Müller <[email protected]>

Author: ingomueller-net

mlir/include/mlir/Bindings/Python/Nanobind.h

@@ -30,6 +30,7 @@
 #include <nanobind/stl/string_view.h>
 #include <nanobind/stl/tuple.h>
 #include <nanobind/stl/vector.h>
+#include <nanobind/typing.h>
 #if defined(__clang__) || defined(__GNUC__)
 #pragma GCC diagnostic pop
 #endif

mlir/lib/Bindings/Python/MainModule.cpp

@@ -24,6 +24,8 @@ using namespace mlir::python;
 
 NB_MODULE(_mlir, m) {
   m.doc() = "MLIR Python Native Extension";
+  m.attr("T") = nb::type_var("T");
+  m.attr("U") = nb::type_var("U");
 
   nb::class_<PyGlobals>(m, "_Globals")
       .def_prop_rw("dialect_search_modules",
@@ -102,6 +104,8 @@ NB_MODULE(_mlir, m) {
               return opClass;
             });
       },
+      nb::sig("def register_operation(dialect_class: type, *, "
+              "replace: bool = False) -> typing.Callable[[type[T]], type[T]]"),
       "dialect_class"_a, nb::kw_only(), "replace"_a = false,
       "Produce a class decorator for registering an Operation class as part of "
       "a dialect");
@@ -114,6 +118,10 @@ NB_MODULE(_mlir, m) {
           return typeCaster;
         });
       },
+      nb::sig("def register_type_caster(typeid: _mlir.ir.TypeID, *, "
+              "replace: bool = False) "
+              "-> typing.Callable[[typing.Callable[[T], U]], "
+              "typing.Callable[[T], U]]"),
       "typeid"_a, nb::kw_only(), "replace"_a = false,
       "Register a type caster for casting MLIR types to custom user types.");
   m.def(
@@ -126,6 +134,10 @@ NB_MODULE(_mlir, m) {
               return valueCaster;
             });
       },
+      nb::sig("def register_value_caster(typeid: _mlir.ir.TypeID, *, "
+              "replace: bool = False) "
+              "-> typing.Callable[[typing.Callable[[T], U]], "
+              "typing.Callable[[T], U]]"),
       "typeid"_a, nb::kw_only(), "replace"_a = false,
       "Register a value caster for casting MLIR values to custom user values.");