Migrate return type void to () for native functions. (#28290)

Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/28290

ghstack-source-id: 92368250

Test Plan:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/28290
ghstack-source-id: 92368250

Differential Revision: D17565528

fbshipit-source-id: f4870bb9ee4f4e7c48df4d68508b512d25ed277c

aten/src/ATen/function_wrapper.py

@@ -887,7 +887,9 @@ def create_generic(top_env, declarations):
 
     def format_return_type(return_types):
         # type: (List[ReturnType]) -> str
-        if len(return_types) == 1:
+        if len(return_types) == 0:
+            return "void"
+        elif len(return_types) == 1:
             return return_types[0]['type']
         return "std::tuple<{}>".format(','.join(r['type'] for r in return_types))
 
@@ -1116,9 +1118,6 @@ def create_generic(top_env, declarations):
             if isinstance(t_raw, string_type):
                 t = t_raw
                 name = None
-            elif t_raw is None:
-                t = 'void'
-                name = None
             else:
                 t = t_raw['type']
                 name = t_raw['name']
@@ -1149,7 +1148,6 @@ def create_generic(top_env, declarations):
         assert option['python_module'] == '' or option['python_module'] == 'nn', \
             "Found python_module of {} for decl {}, but only \'\' string or \'nn\' are supported".format(
                 option['python_module'], option['name'])
-
         formals = native_get_formals(option)
         option['formals_list'] = formals
         option['formals'] = [format_formal(f) for f in formals]

aten/src/ATen/native/native_functions.yaml

@@ -37,10 +37,11 @@
   use_c10_dispatcher: full
   variants: function
 
-- func: backward(Tensor self, Tensor? gradient=None, bool keep_graph=False, bool create_graph=False) -> void
+- func: backward(Tensor self, Tensor? gradient=None, bool keep_graph=False, bool create_graph=False) -> ()
   variants: method
 
-- func: set_data(Tensor(a!) self, Tensor new_data) -> void
+- func: set_data(Tensor(a!) self, Tensor new_data) -> ()
+  use_c10_dispatcher: unboxed_only
   variants: method
 
 - func: data(Tensor self) -> Tensor
@@ -1403,9 +1404,11 @@
 - func: _cufft_get_plan_cache_max_size(int device_index) -> int
   use_c10_dispatcher: full
 
-- func: _cufft_set_plan_cache_max_size(int device_index, int max_size) -> void
+- func: _cufft_set_plan_cache_max_size(int device_index, int max_size) -> ()
+  use_c10_dispatcher: unboxed_only
 
-- func: _cufft_clear_plan_cache(int device_index) -> void
+- func: _cufft_clear_plan_cache(int device_index) -> ()
+  use_c10_dispatcher: unboxed_only
 
 - func: index.Tensor(Tensor self, Tensor?[] indices) -> Tensor
   variants: function, method
@@ -1459,7 +1462,7 @@
   variants: function
   device_guard: False
   supports_named_tensor: True
-  
+
 - func: is_distributed(Tensor self) -> bool
   use_c10_dispatcher: full
   variants: function, method

aten/src/ATen/native_parse.py

@@ -310,7 +310,7 @@ def parse_arguments(args, func_variants, declaration, func_return):
 
     # TODO: Explicit checking for void is a hack and should disappear after a more
     # functionally complete implementation of Tensor aliases.
-    if declaration['inplace'] and len(func_return) > 0 and func_return[0]['type'] != "void":
+    if declaration['inplace'] and len(func_return) > 0:
         found_self = False
         for arg_idx, argument in enumerate(arguments):
             if argument['name'] == "self":
@@ -331,12 +331,15 @@ def parse_arguments(args, func_variants, declaration, func_return):
 
 def parse_return_arguments(return_decl, inplace, func_decl):
     arguments = []
+    if return_decl == '()':
+        return arguments
+
     # TODO: Use a real parser here; this will get bamboozled
     # by signatures that contain things like std::array<bool, 2> (note the space)
     if return_decl[0] == '(' and return_decl[-1] == ')':
         return_decl = return_decl[1:-1]
-    multiple_args = len(return_decl.split(', ')) > 1
 
+    multiple_args = len(return_decl.split(', ')) > 1
     for arg_idx, arg in enumerate(return_decl.split(', ')):
         t, name, default, nullable, size, annotation = type_argument_translations(arg)
         # name of arguments and name of return sometimes have collision

caffe2/contrib/aten/gen_op.py

@@ -124,6 +124,10 @@ def supports(o, factory_methods):
     if "_out" in o['name']:
         return False
 
+    # skip if no return, previously it is 'void'
+    if len(o['returns']) == 0:
+        return False
+
     # skip return types we cannot handle
     for ret in o['returns']:
         if not value_has_tensors(ret) and ret['type'] not in RETURN_MAP:

test/test_namedtuple_return_api.py

@@ -33,6 +33,8 @@ class TestNamedTupleAPI(unittest.TestCase):
                 continue
             if not ret.startswith('('):
                 continue
+            if ret == '()':
+                continue
             ret = ret[1:-1].split(',')
             for r in ret:
                 r = r.strip()

tools/autograd/gen_variable_type.py

@@ -509,7 +509,7 @@ def emit_body(declaration):
     inplace = declaration['inplace']
     is_out_fn = name.endswith('_out')
     modifies_arguments = inplace or is_out_fn
-    returns_void = len(returns) == 1 and returns[0]['type'] == 'void'
+    returns_void = len(returns) == 0
 
     base_name = name[:-1] if inplace else name[:-4] if is_out_fn else name
     view_info = VIEW_FUNCTIONS.get(base_name, None)

tools/jit/gen_jit_dispatch.py

@@ -203,7 +203,8 @@ def is_jit_arg(i, arg):
 
 def is_jit_op(decl):
     # We currently don't support functions that return nothing
-    if all(r['type'] == 'void' for r in decl['returns']):
+    assert all(r['type'] != 'void' for r in decl['returns'])
+    if len(decl['returns']) == 0:
         return False
 
     arguments = decl['arguments']

tools/pyi/gen_pyi.py

@@ -284,8 +284,10 @@ def generate_type_hints(fname, decls, is_tensor=False):
 
         if len(python_returns) > 1:
             python_returns_s = 'Tuple[' + ', '.join(python_returns) + ']'
-        else:
+        elif len(python_returns) == 1:
             python_returns_s = python_returns[0]
+        else:
+            python_returns_s = 'None'
 
         type_hint = "def {}({}) -> {}: ...".format(fname, python_args_s, python_returns_s)
         numargs = len(decl['arguments'])