Replace GetAttr with GetMember. (#63)

`GetAttr` currently gets the type of a member. This naming is
inconsistent since we distinguish between `Attrs` and `Members`, and
also `Attrs` returns `Member` types.

- Rename `GetAttr` to `GetMemberType`.
- Add `GetMember` to access specific members.

Author: dnwpark

pep.rst

@@ -574,8 +574,8 @@ Basic operators
   cannot be.
 
 
-* ``GetAttr[T, S: Literal[str]]``: Extract the type of the member
-  named ``S`` from the class ``T``.
+* ``GetMemberType[T, S: Literal[str]]``: Extract the type of the
+  member named ``S`` from the class ``T``.
 
 * ``Length[T: tuple]`` - get the length of a tuple as an int literal
   (or ``Literal[None]`` if it is unbounded)
@@ -604,6 +604,9 @@ Object inspection
 * ``Attrs[T]``: like ``Members[T]`` but only returns attributes (not
   methods).
 
+* ``GetMember[T, S: Literal[str]]``: Produces a ``Member`` type for the
+  member named ``S`` from the class ``T``.
+
 * ``Member[N: Literal[str], T, Q: MemberQuals, Init, D]``: ``Member``,
   is a simple type, not an operator, that is used to describe members
   of classes.  Its type parameters encode the information about each
@@ -901,7 +904,7 @@ type-annotated attribute of ``K``, while calling ``NewProtocol`` with
 
 ``GetName`` is a getter operator that fetches the name of a ``Member``
 as a literal type--all of these mechanisms lean very heavily on literal types.
-``GetAttr`` gets the type of an attribute from a class.
+``GetMemberType`` gets the type of an attribute from a class.
 
 ::
 
@@ -914,7 +917,7 @@ as a literal type--all of these mechanisms lean very heavily on literal types.
             *[
                 Member[
                     GetName[c],
-                    ConvertField[GetAttr[ModelT, GetName[c]]],
+                    ConvertField[GetMemberType[ModelT, GetName[c]]],
                 ]
                 for c in Iter[Attrs[K]]
             ]
@@ -1183,7 +1186,8 @@ We could do potentially better but it would require more meachinery.
 * ``Member[T]``, when statically checking a type alias, could be
   treated as having some type like ``tuple[Member[KeyOf[T], object,
   str, ..., ...], ...]``
-* ``GetAttr[T, S: KeyOf[T]]`` - but this isn't supported yet. TS supports it.
+* ``GetMemberType[T, S: KeyOf[T]]`` - but this isn't supported yet.
+  TS supports it.
 * We would also need to do context sensitive type bound inference
 
 

tests/test_fastapilike_2.py

@@ -18,7 +18,7 @@
     IsSub,
     FromUnion,
     GetArg,
-    GetAttr,
+    GetMemberType,
     GetType,
     GetName,
     GetQuals,
@@ -46,7 +46,7 @@ class Field[T: FieldArgs](InitField[T]):
 ####
 
 # TODO: Should this go into the stdlib?
-type GetFieldItem[T: InitField, K] = GetAttr[
+type GetFieldItem[T: InitField, K] = GetMemberType[
     GetArg[T, InitField, Literal[0]], K
 ]
 

tests/test_qblike.py

@@ -16,7 +16,7 @@
     GetType,
     Member,
     GetName,
-    GetAttr,
+    GetMemberType,
     GetArg,
 )
 
@@ -49,7 +49,7 @@ def select[K: BaseTypedDict](
     *[
         Member[
             GetName[c],
-            FilterLinks[GetAttr[A, GetName[c]]],
+            FilterLinks[GetMemberType[A, GetName[c]]],
         ]
         for c in Iter[Attrs[K]]
     ]
@@ -118,7 +118,7 @@ class select[...]:
             z: tests.test_qblike.Link[tests.test_qblike.PropsOnly[tests.test_qblike.Tgt]]
         """)
 
-    res = eval_typing(GetAttr[ret, Literal["z"]])
+    res = eval_typing(GetMemberType[ret, Literal["z"]])
     tgt = res.__args__[0]
     # XXX: this should probably be pre-evaluated already?
     tgt = eval_typing(tgt)

tests/test_qblike_2.py

@@ -12,7 +12,7 @@
     GetType,
     Member,
     GetName,
-    GetAttr,
+    GetMemberType,
     GetArg,
 )
 
@@ -58,7 +58,7 @@ class MultiLink[T](Link[T]):
 
 ``GetName`` is a getter operator that fetches the name of a ``Member``
 as a literal type--all of these mechanisms lean very heavily on literal types.
-``GetAttr`` gets the type of an attribute from a class.
+``GetMemberType`` gets the type of an attribute from a class.
 
 """
 
@@ -72,7 +72,7 @@ def select[ModelT, K: BaseTypedDict](
         *[
             Member[
                 GetName[c],
-                ConvertField[GetAttr[ModelT, GetName[c]]],
+                ConvertField[GetMemberType[ModelT, GetName[c]]],
             ]
             for c in Iter[Attrs[K]]
         ]
@@ -198,7 +198,7 @@ class select[...]:
             posts: list[tests.test_qblike_2.PropsOnly[tests.test_qblike_2.Post]]
         """)
 
-    res = eval_typing(GetAttr[ret, Literal["posts"]])
+    res = eval_typing(GetMemberType[ret, Literal["posts"]])
     tgt = res.__args__[0]
     # XXX: this should probably be pre-evaluated already?
     fmt = format_helper.format_class(tgt)

tests/test_type_eval.py

@@ -25,7 +25,8 @@
     GenericCallable,
     GetArg,
     GetArgs,
-    GetAttr,
+    GetMember,
+    GetMemberType,
     GetName,
     GetType,
     GetAnnotations,
@@ -198,27 +199,27 @@ def test_eval_arg_order():
 
 
 def test_type_getattr_union_1():
-    d = eval_typing(GetAttr[TA | TB, Literal["x"]])
+    d = eval_typing(GetMemberType[TA | TB, Literal["x"]])
     assert d == int | str
 
 
 def test_type_getattr_union_2():
-    d = eval_typing(GetAttr[TA, Literal["x"] | Literal["y"]])
+    d = eval_typing(GetMemberType[TA, Literal["x"] | Literal["y"]])
     assert d == int | list[float]
 
 
 def test_type_getattr_union_3():
-    d = eval_typing(GetAttr[TA | TB, Literal["x"] | Literal["y"]])
+    d = eval_typing(GetMemberType[TA | TB, Literal["x"] | Literal["y"]])
     assert d == int | list[float] | str | list[object]
 
 
 def test_type_getattr_union_4():
-    d = eval_typing(GetAttr[TA, Literal["x", "y"]])
+    d = eval_typing(GetMemberType[TA, Literal["x", "y"]])
     assert d == int | list[float]
 
 
 def test_type_getattr_union_5():
-    d = eval_typing(GetAttr[TA, Literal["x", "y"] | Literal["z"]])
+    d = eval_typing(GetMemberType[TA, Literal["x", "y"] | Literal["z"]])
     assert d == int | list[float] | TB
 
 
@@ -379,6 +380,21 @@ def test_type_from_union_06():
     assert _is_generic_permutation(n, tuple[int, list[IntTree]])
 
 
+def test_getmember_01():
+    d = eval_typing(GetMember[TA, Literal["x"]])
+    assert d == Member[Literal["x"], int, Never, Never, TA]
+    d = eval_typing(GetMemberType[TA, Literal["a"]])
+    assert d == Never
+
+    d = eval_typing(GetMember[TA | TB, Literal["x"]])
+    assert d == (
+        Member[Literal["x"], int, Never, Never, TA]
+        | Member[Literal["x"], str, Never, Never, TB]
+    )
+    d = eval_typing(GetMember[TA | TB, Literal[""]])
+    assert d == Never
+
+
 def test_getarg_never():
     d = eval_typing(GetArg[Never, object, Literal[0]])
     assert d is Never
@@ -1537,15 +1553,15 @@ class AnnoTest:
 
 
 def test_type_eval_annotated_02():
-    res = eval_typing(IsSub[GetAttr[AnnoTest, Literal["a"]], int])
+    res = eval_typing(IsSub[GetMemberType[AnnoTest, Literal["a"]], int])
     assert res == _BoolLiteral[True]
 
 
 def test_type_eval_annotated_03():
-    res = eval_typing(Uppercase[GetAttr[AnnoTest, Literal["b"]]])
+    res = eval_typing(Uppercase[GetMemberType[AnnoTest, Literal["b"]]])
     assert res == Literal["TEST"]
 
 
 def test_type_eval_annotated_04():
-    res = eval_typing(GetAnnotations[GetAttr[AnnoTest, Literal["b"]]])
+    res = eval_typing(GetAnnotations[GetMemberType[AnnoTest, Literal["b"]]])
     assert res == Literal["blah"]

typemap/type_eval/_eval_operators.py

@@ -25,7 +25,8 @@
     GetAnnotations,
     GetArg,
     GetArgs,
-    GetAttr,
+    GetMember,
+    GetMemberType,
     InitField,
     IsSubSimilar,
     IsSubtype,
@@ -657,19 +658,20 @@ def _get_function_hint_namespaces(func, receiver_type=None):
     return globalns, localns
 
 
+def _hint_to_member(n, t, qs, init, d, *, ctx):
+    return Member[
+        typing.Literal[n],
+        _eval_types(t, ctx),
+        _mk_literal_union(*qs),
+        init,
+        d,
+    ]
+
+
 def _hints_to_members(hints, ctx):
     """Convert a hints dictionary to a tuple of Member types."""
     return tuple[
-        *[
-            Member[
-                typing.Literal[n],
-                _eval_types(t, ctx),
-                _mk_literal_union(*qs),
-                init,
-                d,
-            ]
-            for n, (t, qs, init, d) in hints.items()
-        ]
+        *[_hint_to_member(n, *hint, ctx=ctx) for n, hint in hints.items()]
     ]
 
 
@@ -690,6 +692,21 @@ def _eval_Members(tp, *, ctx):
     return _hints_to_members(hints, ctx)
 
 
+@type_eval.register_evaluator(GetMember)
+@_lift_over_unions
+def _eval_GetMember(tp, prop, *, ctx):
+    # XXX: extras?
+    name = _from_literal(prop)
+    hints = {
+        **get_annotated_type_hints(tp, include_extras=True),
+        **get_annotated_method_hints(tp),
+    }
+    if name in hints:
+        return _hint_to_member(name, *hints[name], ctx=ctx)
+    else:
+        return typing.Never
+
+
 ##################################################################
 
 
@@ -705,9 +722,9 @@ def _eval_FromUnion(tp, *, ctx):
 ##################################################################
 
 
-@type_eval.register_evaluator(GetAttr)
+@type_eval.register_evaluator(GetMemberType)
 @_lift_over_unions
-def _eval_GetAttr(tp, prop, *, ctx):
+def _eval_GetMemberType(tp, prop, *, ctx):
     # XXX: extras?
     name = _from_literal(prop)
     hints = {

typemap/typing.py

@@ -112,11 +112,11 @@ class Param[N: str | None, T, Q: ParamQuals = typing.Never]:
 type KwargsParam[T] = Param[Literal[None], T, Literal["**"]]
 
 
-type GetName[T: Member | Param] = GetAttr[T, Literal["name"]]
-type GetType[T: Member | Param] = GetAttr[T, Literal["typ"]]
-type GetQuals[T: Member | Param] = GetAttr[T, Literal["quals"]]
-type GetInit[T: Member] = GetAttr[T, Literal["init"]]
-type GetDefiner[T: Member] = GetAttr[T, Literal["definer"]]
+type GetName[T: Member | Param] = GetMemberType[T, Literal["name"]]
+type GetType[T: Member | Param] = GetMemberType[T, Literal["typ"]]
+type GetQuals[T: Member | Param] = GetMemberType[T, Literal["quals"]]
+type GetInit[T: Member] = GetMemberType[T, Literal["init"]]
+type GetDefiner[T: Member] = GetMemberType[T, Literal["definer"]]
 
 
 class Attrs[T]:
@@ -131,7 +131,11 @@ class FromUnion[T]:
     pass
 
 
-class GetAttr[Lhs, Prop]:
+class GetMember[Lhs, Prop]:
+    pass
+
+
+class GetMemberType[Lhs, Prop]:
     pass