Add GetSpecialAttr. (#61)

Allows getting the `__name__`, `__module__`, `__qualname__` special
attributes.

```py
    d = eval_typing(GetSpecialAttr[int, Literal["__name__"]])
    assert d == Literal["int"]
    d = eval_typing(GetSpecialAttr[list[int], Literal["__name__"]])
    assert d == Literal["list"]

    d = eval_typing(GetSpecialAttr[C, Literal["__name__"]])
    assert d == Literal["C"]
    d = eval_typing(GetSpecialAttr[C, Literal["__module__"]])
    assert d == Literal["tests.test_type_eval"]
    d = eval_typing(GetSpecialAttr[C, Literal["__qualname__"]])
    assert d == Literal["test_eval_typename_03.<locals>.C"]
```

Author: dnwpark

pep.rst

@@ -580,6 +580,13 @@ Basic operators
 * ``GetMemberType[T, S: Literal[str]]``: Extract the type of the
   member named ``S`` from the class ``T``.
 
+
+* ``GetSpecialAttr[T: type, Attr: Literal[str]]``: Extract the value
+  of special attribute named ``Attr`` from the class ``T``. Valid
+  attributes are ``__name__``, ``__module__``, and ``__qualname__``.
+  Returns the value as a ``Literal[str]``.
+
+
 * ``Length[T: tuple]`` - get the length of a tuple as an int literal
   (or ``Literal[None]`` if it is unbounded)
 

tests/test_type_eval.py

@@ -28,6 +28,7 @@
     GetMember,
     GetMemberType,
     GetName,
+    GetSpecialAttr,
     GetType,
     GetAnnotations,
     IsSub,
@@ -990,6 +991,85 @@ class Container2[T]: ...
     assert eval_typing(GetArg[t, Container, Literal[1]]) == Never
 
 
+class OuterType:
+    class InnerType:
+        pass
+
+
+def test_eval_typename_01():
+    d = eval_typing(GetSpecialAttr[int, Literal["__name__"]])
+    assert d == Literal["int"]
+    d = eval_typing(GetSpecialAttr[str, Literal["__name__"]])
+    assert d == Literal["str"]
+    d = eval_typing(GetSpecialAttr[list[int], Literal["__name__"]])
+    assert d == Literal["list"]
+    d = eval_typing(GetSpecialAttr[list[str], Literal["__name__"]])
+    assert d == Literal["list"]
+
+    class C:
+        pass
+
+    d = eval_typing(GetSpecialAttr[OuterType, Literal["__name__"]])
+    assert d == Literal["OuterType"]
+    d = eval_typing(GetSpecialAttr[OuterType.InnerType, Literal["__name__"]])
+    assert d == Literal["InnerType"]
+    d = eval_typing(GetSpecialAttr[C, Literal["__name__"]])
+    assert d == Literal["C"]
+
+    d = eval_typing(GetSpecialAttr[GetA1[int, str], Literal["__name__"]])
+    assert d == Literal["int"]
+
+
+def test_eval_typename_02():
+    d = eval_typing(GetSpecialAttr[int, Literal["__module__"]])
+    assert d == Literal["builtins"]
+    d = eval_typing(GetSpecialAttr[str, Literal["__module__"]])
+    assert d == Literal["builtins"]
+    d = eval_typing(GetSpecialAttr[list[int], Literal["__module__"]])
+    assert d == Literal["builtins"]
+    d = eval_typing(GetSpecialAttr[list[str], Literal["__module__"]])
+    assert d == Literal["builtins"]
+
+    class C:
+        pass
+
+    d = eval_typing(GetSpecialAttr[OuterType, Literal["__module__"]])
+    assert d == Literal["tests.test_type_eval"]
+    d = eval_typing(GetSpecialAttr[OuterType.InnerType, Literal["__module__"]])
+    assert d == Literal["tests.test_type_eval"]
+    d = eval_typing(GetSpecialAttr[C, Literal["__module__"]])
+    assert d == Literal["tests.test_type_eval"]
+
+    d = eval_typing(GetSpecialAttr[GetA1[int, str], Literal["__module__"]])
+    assert d == Literal["builtins"]
+
+
+def test_eval_typename_03():
+    d = eval_typing(GetSpecialAttr[int, Literal["__qualname__"]])
+    assert d == Literal["int"]
+    d = eval_typing(GetSpecialAttr[str, Literal["__qualname__"]])
+    assert d == Literal["str"]
+    d = eval_typing(GetSpecialAttr[list[int], Literal["__qualname__"]])
+    assert d == Literal["list"]
+    d = eval_typing(GetSpecialAttr[list[str], Literal["__qualname__"]])
+    assert d == Literal["list"]
+
+    class C:
+        pass
+
+    d = eval_typing(GetSpecialAttr[OuterType, Literal["__qualname__"]])
+    assert d == Literal["OuterType"]
+    d = eval_typing(
+        GetSpecialAttr[OuterType.InnerType, Literal["__qualname__"]]
+    )
+    assert d == Literal["OuterType.InnerType"]
+    d = eval_typing(GetSpecialAttr[C, Literal["__qualname__"]])
+    assert d == Literal["test_eval_typename_03.<locals>.C"]
+
+    d = eval_typing(GetSpecialAttr[GetA1[int, str], Literal["__qualname__"]])
+    assert d == Literal["int"]
+
+
 type _Works[Ts, I] = Literal[True]
 type Works[Ts] = _Works[Ts, Length[Ts]]
 

typemap/type_eval/_eval_operators.py

@@ -27,6 +27,7 @@
     GetArgs,
     GetMember,
     GetMemberType,
+    GetSpecialAttr,
     InitField,
     IsSubSimilar,
     IsSubtype,
@@ -923,6 +924,28 @@ def _eval_GetArgs(tp, base, *, ctx) -> typing.Any:
     return tuple[*args]  # type: ignore[valid-type]
 
 
+@type_eval.register_evaluator(GetSpecialAttr)
+@_lift_over_unions
+def _eval_GetSpecialAttr(tp, attr, *, ctx) -> typing.Any:
+    if not (
+        _typing_inspect.is_generic_alias(attr)
+        and attr.__origin__ is typing.Literal
+        and isinstance(attr.__args__[0], str)
+    ):
+        raise TypeError(
+            f"Invalid type argument to GetSpecialAttr: "
+            f"{attr} is not a string Literal"
+        )
+    if attr.__args__[0] == "__name__":
+        return typing.Literal[tp.__name__]
+    elif attr.__args__[0] == "__module__":
+        return typing.Literal[tp.__module__]
+    elif attr.__args__[0] == "__qualname__":
+        return typing.Literal[tp.__qualname__]
+    else:
+        return typing.Never
+
+
 @type_eval.register_evaluator(GetAnnotations)
 def _eval_GetAnnotations(tp, *, ctx) -> typing.Any:
     tp = _eval_types(tp, ctx=ctx)

typemap/typing.py

@@ -147,6 +147,10 @@ class GetArgs[Tp, Base]:
     pass
 
 
+class GetSpecialAttr[T: type, Attr: str]:
+    pass
+
+
 class Length[S: tuple]:
     pass