[CORE] Add TypeConverter for runtime type validation/conversion

Add a TypeConverter system to the Cython FFI module that takes a
TypeSchema and returns a Function wrapping a C++ conversion function
(Any) -> Any. The converter validates/converts input values to match
the target type, with fast-path (zero-copy) for containers when
elements already match and slow-path (element-by-element conversion)
otherwise.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: junrushao

CMakeLists.txt

@@ -247,6 +247,7 @@ if (TVM_FFI_BUILD_PYTHON_MODULE)
       ${CMAKE_CURRENT_SOURCE_DIR}/python/tvm_ffi/cython/tensor.pxi
       ${CMAKE_CURRENT_SOURCE_DIR}/python/tvm_ffi/cython/object.pxi
       ${CMAKE_CURRENT_SOURCE_DIR}/python/tvm_ffi/cython/string.pxi
+      ${CMAKE_CURRENT_SOURCE_DIR}/python/tvm_ffi/cython/type_converter.pxi
   )
   # Run a Python script to check for free-threaded build
   execute_process(

python/tvm_ffi/__init__.py

@@ -46,7 +46,7 @@
     init_ffi_api,
 )
 from ._dtype import dtype
-from .core import Object, ObjectConvertible, Function
+from .core import Object, ObjectConvertible, Function, create_type_converter
 from ._convert import convert
 from .error import register_error
 from ._tensor import Device, device, DLDeviceType
@@ -118,6 +118,7 @@
     "access_path",
     "convert",
     "cpp",
+    "create_type_converter",
     "dataclasses",
     "device",
     "dtype",

python/tvm_ffi/core.pyi

@@ -269,3 +269,5 @@ class TypeInfo:
     parent_type_info: TypeInfo | None
 
     def prototype_py(self) -> str: ...
+
+def create_type_converter(schema: TypeSchema) -> Function: ...

python/tvm_ffi/cython/core.pyx

@@ -38,6 +38,7 @@ include "./tensor.pxi"
 _register_object_by_index(kTVMFFITensor, Tensor)
 include "./function.pxi"
 _register_object_by_index(kTVMFFIFunction, Function)
+include "./type_converter.pxi"
 
 # Global invalid/missing object singleton
 MISSING = _get_global_func("ffi.GetInvalidObject", False)()