jcrist · jcrist · Dec 8, 2023 · Dec 8, 2023
diff --git a/docs/source/supported-types.rst b/docs/source/supported-types.rst
@@ -49,6 +49,8 @@ Most combinations of the following types are supported (with a few restrictions)
 - `typing.Literal`
 - `typing.NewType`
 - `typing.Final`
+- `typing.TypeAliasType`
+- `typing.TypeAlias`
 - `typing.NamedTuple` / `collections.namedtuple`
 - `typing.TypedDict`
 - `typing.Generic`
@@ -1170,6 +1172,36 @@ support here is purely to aid static analysis tools like mypy_ or pyright_.
  File "<stdin>", line 1, in <module>
  msgspec.ValidationError: Expected `int`, got `str`
 
+Type Aliases
+------------
+
+For complex types, sometimes it can be nice to write the type once so you can
+reuse it later.
+
+.. code-block:: python
+
+ Point = tuple[float, float]
+
+Here ``Point`` is a "type alias" for ``tuple[float, float]`` - ``msgspec``
+will substitute in ``tuple[float, float]`` whenever the ``Point`` type
+is used in an annotation.
+
+``msgspec`` supports the following equivalent forms:
+
+.. code-block:: python
+
+ # Using variable assignment
+ Point = tuple[float, float]
+
+ # Using variable assignment, annotated as a `TypeAlias`
+ Point: TypeAlias = tuple[float, float]
+
+ # Using Python 3.12's new `type` statement. This only works on Python 3.12+
+ type Point = tuple[float, float]
+
+To learn more about Type Aliases, see Python's `Type Alias docs here
+<https://docs.python.org/3/library/typing.html#type-aliases>`__.
+
 Generic Types
 -------------
 

diff --git a/msgspec/_core.c b/msgspec/_core.c
@@ -15,6 +15,12 @@
 #include "ryu.h"
 #include "atof.h"
 
+/* Python version checks */
+#define PY39_PLUS (PY_VERSION_HEX >= 0x03090000)
+#define PY310_PLUS (PY_VERSION_HEX >= 0x030a0000)
+#define PY311_PLUS (PY_VERSION_HEX >= 0x030b0000)
+#define PY312_PLUS (PY_VERSION_HEX >= 0x030c0000)
+
 /* Hint to the compiler not to store `x` in a register since it is likely to
  * change. Results in much higher performance on GCC, with smaller benefits on
  * clang */
@@ -36,18 +42,18 @@ ms_popcount(uint64_t i) { \
 }
 #endif
 
-#if PY_VERSION_HEX < 0x03090000
-#define CALL_ONE_ARG(f, a) PyObject_CallFunctionObjArgs(f, a, NULL)
-#define CALL_NO_ARGS(f) PyObject_CallFunctionObjArgs(f, NULL)
-#define CALL_METHOD_ONE_ARG(o, n, a) PyObject_CallMethodObjArgs(o, n, a, NULL)
-#define CALL_METHOD_NO_ARGS(o, n) PyObject_CallMethodObjArgs(o, n, NULL)
-#define SET_SIZE(obj, size) (((PyVarObject *)obj)->ob_size = size)
-#else
+#if PY39_PLUS
 #define CALL_ONE_ARG(f, a) PyObject_CallOneArg(f, a)
 #define CALL_NO_ARGS(f) PyObject_CallNoArgs(f)
 #define CALL_METHOD_ONE_ARG(o, n, a) PyObject_CallMethodOneArg(o, n, a)
 #define CALL_METHOD_NO_ARGS(o, n) PyObject_CallMethodNoArgs(o, n)
 #define SET_SIZE(obj, size) Py_SET_SIZE(obj, size)
+#else
+#define CALL_ONE_ARG(f, a) PyObject_CallFunctionObjArgs(f, a, NULL)
+#define CALL_NO_ARGS(f) PyObject_CallFunctionObjArgs(f, NULL)
+#define CALL_METHOD_ONE_ARG(o, n, a) PyObject_CallMethodObjArgs(o, n, a, NULL)
+#define CALL_METHOD_NO_ARGS(o, n) PyObject_CallMethodObjArgs(o, n, NULL)
+#define SET_SIZE(obj, size) (((PyVarObject *)obj)->ob_size = size)
 #endif
 
 #define DIV_ROUND_CLOSEST(n, d) ((((n) < 0) == ((d) < 0)) ? (((n) + (d)/2)/(d)) : (((n) - (d)/2)/(d)))
@@ -157,7 +163,7 @@ fast_long_extract_parts(PyObject *vv, bool *neg, uint64_t *scale) {
  uint64_t prev, x = 0;
  bool negative;
 
-#if PY_VERSION_HEX >= 0x030c0000
+#if PY312_PLUS
  /* CPython 3.12 changed int internal representation */
  int sign = 1 - (v->long_value.lv_tag & _PyLong_SIGN_MASK);
  negative = sign == -1;
@@ -405,6 +411,9 @@ typedef struct {
  PyObject *str___dataclass_fields__;
  PyObject *str___attrs_attrs__;
  PyObject *str___supertype__;
+#if PY312_PLUS
+ PyObject *str___value__;
+#endif
  PyObject *str___bound__;
  PyObject *str___constraints__;
  PyObject *str_int;
@@ -427,8 +436,11 @@ typedef struct {
  PyObject *get_typeddict_info;
  PyObject *get_dataclass_info;
  PyObject *rebuild;
-#if PY_VERSION_HEX >= 0x030a00f0
+#if PY310_PLUS
  PyObject *types_uniontype;
+#endif
+#if PY312_PLUS
+ PyObject *typing_typealiastype;
 #endif
  PyObject *astimezone;
  PyObject *re_compile;
@@ -2122,7 +2134,7 @@ PyTypeObject NoDefault_Type = {
  .tp_basicsize = 0
 };
 
-#if PY_VERSION_HEX >= 0x030c0000
+#if PY312_PLUS
 PyObject _NoDefault_Object = {
  _PyObject_EXTRA_INIT
  { _Py_IMMORTAL_REFCNT },
@@ -2226,7 +2238,7 @@ PyTypeObject Unset_Type = {
  .tp_basicsize = 0
 };
 
-#if PY_VERSION_HEX >= 0x030c0000
+#if PY312_PLUS
 PyObject _Unset_Object = {
  _PyObject_EXTRA_INIT
  { _Py_IMMORTAL_REFCNT },
@@ -4459,6 +4471,21 @@ typenode_origin_args_metadata(
  t = temp;
  continue;
  }
+ /* Check for parametrized TypeAliasType if Python 3.12+ */
+ #if PY312_PLUS
+ if (Py_TYPE(origin) == (PyTypeObject *)(state->mod->typing_typealiastype)) {
+ PyObject *value = PyObject_GetAttr(origin, state->mod->str___value__);
+ if (value == NULL) goto error;
+ PyObject *temp = PyObject_GetItem(value, args);
+ Py_DECREF(value);
+ if (temp == NULL) goto error;
+ Py_CLEAR(args);
+ Py_CLEAR(origin);
+ Py_DECREF(t);
+ t = temp;
+ continue;
+ }
+ #endif
  }
  else {
  /* Custom non-parametrized generics won't have __args__
@@ -4487,14 +4514,23 @@ typenode_origin_args_metadata(
  t = supertype;
  continue;
  }
- else {
- PyErr_Clear();
- break;
+ PyErr_Clear();
+
+ /* Check for TypeAliasType if Python 3.12+ */
+ #if PY312_PLUS
+ if (Py_TYPE(t) == (PyTypeObject *)(state->mod->typing_typealiastype)) {
+ PyObject *value = PyObject_GetAttr(t, state->mod->str___value__);
+ if (value == NULL) goto error;
+ Py_DECREF(t);
+ t = value;
+ continue;
  }
+ #endif
+ break;
  }
  }
 
- #if PY_VERSION_HEX >= 0x030a00f0
+ #if PY310_PLUS
  if (Py_TYPE(t) == (PyTypeObject *)(state->mod->types_uniontype)) {
  /* Handle types.UnionType unions (`int | float | ...`) */
  args = PyObject_GetAttr(t, state->mod->str___args__);
@@ -4692,13 +4728,18 @@ typenode_collect_type(TypeNodeCollectState *state, PyObject *obj) {
  }
  }
  else if (origin == state->mod->typing_union) {
+ if (Py_EnterRecursiveCall(" while analyzing a type")) {
+ out = -1;
+ goto done;
+ }
  for (Py_ssize_t i = 0; i < PyTuple_GET_SIZE(args); i++) {
  PyObject *arg = PyTuple_GET_ITEM(args, i);
  /* Ignore UnsetType in unions */
  if (arg == (PyObject *)(&Unset_Type)) continue;
  out = typenode_collect_type(state, arg);
  if (out < 0) break;
  }
+ Py_LeaveRecursiveCall();
  }
  else if (origin == state->mod->typing_literal) {
  if (state->literals == NULL) {
@@ -4761,6 +4802,8 @@ TypeNode_Convert(PyObject *obj) {
  state.mod = msgspec_get_global_state();
  state.context = obj;
 
+ if (Py_EnterRecursiveCall(" while analyzing a type")) return NULL;
+
  /* Traverse `obj` to collect all type annotations at this level */
  if (typenode_collect_type(&state, obj) < 0) goto done;
  /* Handle structs in a second pass */
@@ -4773,6 +4816,7 @@ TypeNode_Convert(PyObject *obj) {
  out = typenode_from_collect_state(&state);
 done:
  typenode_collect_clear_state(&state);
+ Py_LeaveRecursiveCall();
  return out;
 }
 
@@ -9717,14 +9761,14 @@ ms_encode_err_type_unsupported(PyTypeObject *type) {
  *************************************************************************/
 
 #define MS_HAS_TZINFO(o) (((_PyDateTime_BaseTZInfo *)(o))->hastzinfo)
-#if PY_VERSION_HEX < 0x030a00f0
+#if PY310_PLUS
+#define MS_DATE_GET_TZINFO(o) PyDateTime_DATE_GET_TZINFO(o)
+#define MS_TIME_GET_TZINFO(o) PyDateTime_TIME_GET_TZINFO(o)
+#else
 #define MS_DATE_GET_TZINFO(o) (MS_HAS_TZINFO(o) ? \
  ((PyDateTime_DateTime *)(o))->tzinfo : Py_None)
 #define MS_TIME_GET_TZINFO(o) (MS_HAS_TZINFO(o) ? \
  ((PyDateTime_Time *)(o))->tzinfo : Py_None)
-#else
-#define MS_DATE_GET_TZINFO(o) PyDateTime_DATE_GET_TZINFO(o)
-#define MS_TIME_GET_TZINFO(o) PyDateTime_TIME_GET_TZINFO(o)
 #endif
 
 #ifndef TIMEZONE_CACHE_SIZE
@@ -15472,7 +15516,7 @@ static struct PyMethodDef Decoder_methods[] = {
  "decode", (PyCFunction) Decoder_decode, METH_FASTCALL,
  Decoder_decode__doc__,
  },
-#if PY_VERSION_HEX >= 0x03090000
+#if PY39_PLUS
  {"__class_getitem__", Py_GenericAlias, METH_O|METH_CLASS},
 #endif
  {NULL, NULL} /* sentinel */
@@ -18512,7 +18556,7 @@ static struct PyMethodDef JSONDecoder_methods[] = {
  "decode_lines", (PyCFunction) JSONDecoder_decode_lines, METH_FASTCALL,
  JSONDecoder_decode_lines__doc__,
  },
-#if PY_VERSION_HEX >= 0x03090000
+#if PY39_PLUS
  {"__class_getitem__", Py_GenericAlias, METH_O|METH_CLASS},
 #endif
  {NULL, NULL} /* sentinel */
@@ -21029,6 +21073,9 @@ msgspec_clear(PyObject *m)
  Py_CLEAR(st->str___dataclass_fields__);
  Py_CLEAR(st->str___attrs_attrs__);
  Py_CLEAR(st->str___supertype__);
+#if PY312_PLUS
+ Py_CLEAR(st->str___value__);
+#endif
  Py_CLEAR(st->str___bound__);
  Py_CLEAR(st->str___constraints__);
  Py_CLEAR(st->str_int);
@@ -21051,8 +21098,11 @@ msgspec_clear(PyObject *m)
  Py_CLEAR(st->get_typeddict_info);
  Py_CLEAR(st->get_dataclass_info);
  Py_CLEAR(st->rebuild);
-#if PY_VERSION_HEX >= 0x030a00f0
+#if PY310_PLUS
  Py_CLEAR(st->types_uniontype);
+#endif
+#if PY312_PLUS
+ Py_CLEAR(st->typing_typealiastype);
 #endif
  Py_CLEAR(st->astimezone);
  Py_CLEAR(st->re_compile);
@@ -21118,8 +21168,11 @@ msgspec_traverse(PyObject *m, visitproc visit, void *arg)
  Py_VISIT(st->get_typeddict_info);
  Py_VISIT(st->get_dataclass_info);
  Py_VISIT(st->rebuild);
-#if PY_VERSION_HEX >= 0x030a00f0
+#if PY310_PLUS
  Py_VISIT(st->types_uniontype);
+#endif
+#if PY312_PLUS
+ Py_VISIT(st->typing_typealiastype);
 #endif
  Py_VISIT(st->astimezone);
  Py_VISIT(st->re_compile);
@@ -21315,6 +21368,9 @@ PyInit__core(void)
  SET_REF(typing_final, "Final");
  SET_REF(typing_generic, "Generic");
  SET_REF(typing_generic_alias, "_GenericAlias");
+#if PY312_PLUS
+ SET_REF(typing_typealiastype, "TypeAliasType");
+#endif
  Py_DECREF(temp_module);
 
  temp_module = PyImport_ImportModule("msgspec._utils");
@@ -21328,7 +21384,7 @@ PyInit__core(void)
  SET_REF(rebuild, "rebuild");
  Py_DECREF(temp_module);
 
-#if PY_VERSION_HEX >= 0x030a00f0
+#if PY310_PLUS
  temp_module = PyImport_ImportModule("types");
  if (temp_module == NULL) return NULL;
  SET_REF(types_uniontype, "UnionType");
@@ -21411,6 +21467,9 @@ PyInit__core(void)
  CACHED_STRING(str___dataclass_fields__, "__dataclass_fields__");
  CACHED_STRING(str___attrs_attrs__, "__attrs_attrs__");
  CACHED_STRING(str___supertype__, "__supertype__");
+#if PY312_PLUS
+ CACHED_STRING(str___value__, "__value__");
+#endif
  CACHED_STRING(str___bound__, "__bound__");
  CACHED_STRING(str___constraints__, "__constraints__");
  CACHED_STRING(str_int, "int");

diff --git a/msgspec/inspect.py b/msgspec/inspect.py
@@ -20,6 +20,11 @@
 except Exception:
  _types_UnionType = type("UnionType", (), {}) # type: ignore
 
+try:
+ from typing import TypeAliasType as _TypeAliasType # type: ignore
+except Exception:
+ _TypeAliasType = type("TypeAliasType", (), {}) # type: ignore
+
 import msgspec
 from msgspec import NODEFAULT, UNSET, UnsetType as _UnsetType
 
@@ -628,6 +633,8 @@ def _origin_args_metadata(t):
  t = origin
  elif origin == Final:
  t = t.__args__[0]
+ elif type(origin) is _TypeAliasType:
+ t = origin.__value__[t.__args__]
  else:
  args = getattr(t, "__args__", None)
  origin = _CONCRETE_TYPES.get(origin, origin)
@@ -636,6 +643,8 @@ def _origin_args_metadata(t):
  supertype = getattr(t, "__supertype__", None)
  if supertype is not None:
  t = supertype
+ elif type(t) is _TypeAliasType:
+ t = t.__value__
  else:
  origin = t
  args = None