[ty] Fixup a few details around version-specific dataclass features (#21453)

crates/ty_ide/src/completion.rs

@@ -2411,6 +2411,73 @@ Answer.<CURSOR>
         );
     }
 
+    #[test]
+    fn namedtuple_methods() {
+        let builder = completion_test_builder(
+            "\
+from typing import NamedTuple
+
+class Quux(NamedTuple):
+    x: int
+    y: str
+
+quux = Quux()
+quux.<CURSOR>
+",
+        );
+
+        assert_snapshot!(
+            builder.skip_keywords().skip_builtins().type_signatures().build().snapshot(), @r"
+        count :: bound method Quux.count(value: Any, /) -> int
+        index :: bound method Quux.index(value: Any, start: SupportsIndex = Literal[0], stop: SupportsIndex = int, /) -> int
+        x :: int
+        y :: str
+        __add__ :: Overload[(value: tuple[int | str, ...], /) -> tuple[int | str, ...], (value: tuple[_T@__add__, ...], /) -> tuple[int | str | _T@__add__, ...]]
+        __annotations__ :: dict[str, Any]
+        __class__ :: type[Quux]
+        __class_getitem__ :: bound method type[Quux].__class_getitem__(item: Any, /) -> GenericAlias
+        __contains__ :: bound method Quux.__contains__(key: object, /) -> bool
+        __delattr__ :: bound method Quux.__delattr__(name: str, /) -> None
+        __dict__ :: dict[str, Any]
+        __dir__ :: bound method Quux.__dir__() -> Iterable[str]
+        __doc__ :: str | None
+        __eq__ :: bound method Quux.__eq__(value: object, /) -> bool
+        __format__ :: bound method Quux.__format__(format_spec: str, /) -> str
+        __ge__ :: bound method Quux.__ge__(value: tuple[int | str, ...], /) -> bool
+        __getattribute__ :: bound method Quux.__getattribute__(name: str, /) -> Any
+        __getitem__ :: Overload[(index: Literal[-2, 0], /) -> int, (index: Literal[-1, 1], /) -> str, (index: SupportsIndex, /) -> int | str, (index: slice[Any, Any, Any], /) -> tuple[int | str, ...]]
+        __getstate__ :: bound method Quux.__getstate__() -> object
+        __gt__ :: bound method Quux.__gt__(value: tuple[int | str, ...], /) -> bool
+        __hash__ :: bound method Quux.__hash__() -> int
+        __init__ :: bound method Quux.__init__() -> None
+        __init_subclass__ :: bound method type[Quux].__init_subclass__() -> None
+        __iter__ :: bound method Quux.__iter__() -> Iterator[int | str]
+        __le__ :: bound method Quux.__le__(value: tuple[int | str, ...], /) -> bool
+        __len__ :: () -> Literal[2]
+        __lt__ :: bound method Quux.__lt__(value: tuple[int | str, ...], /) -> bool
+        __module__ :: str
+        __mul__ :: bound method Quux.__mul__(value: SupportsIndex, /) -> tuple[int | str, ...]
+        __ne__ :: bound method Quux.__ne__(value: object, /) -> bool
+        __new__ :: (x: int, y: str) -> None
+        __orig_bases__ :: tuple[Any, ...]
+        __reduce__ :: bound method Quux.__reduce__() -> str | tuple[Any, ...]
+        __reduce_ex__ :: bound method Quux.__reduce_ex__(protocol: SupportsIndex, /) -> str | tuple[Any, ...]
+        __replace__ :: bound method NamedTupleFallback.__replace__(**kwargs: Any) -> NamedTupleFallback
+        __repr__ :: bound method Quux.__repr__() -> str
+        __reversed__ :: bound method Quux.__reversed__() -> Iterator[int | str]
+        __rmul__ :: bound method Quux.__rmul__(value: SupportsIndex, /) -> tuple[int | str, ...]
+        __setattr__ :: bound method Quux.__setattr__(name: str, value: Any, /) -> None
+        __sizeof__ :: bound method Quux.__sizeof__() -> int
+        __str__ :: bound method Quux.__str__() -> str
+        __subclasshook__ :: bound method type[Quux].__subclasshook__(subclass: type, /) -> bool
+        _asdict :: bound method NamedTupleFallback._asdict() -> dict[str, Any]
+        _field_defaults :: dict[str, Any]
+        _fields :: tuple[str, ...]
+        _make :: bound method type[NamedTupleFallback]._make(iterable: Iterable[Any]) -> NamedTupleFallback
+        _replace :: bound method NamedTupleFallback._replace(**kwargs: Any) -> NamedTupleFallback
+        ");
+    }
+
     // We don't yet take function parameters into account.
     #[test]
     fn call_prefix1() {

crates/ty_python_semantic/resources/mdtest/dataclasses/dataclasses.md

@@ -667,8 +667,13 @@ reveal_type(B.__slots__)  # revealed: tuple[Literal["x"], Literal["y"]]
 
 ### `weakref_slot`
 
-When a dataclass is defined with `weakref_slot=True`, the `__weakref__` attribute is generated. For
-now, we do not attempt to infer a more precise type for it.
+When a dataclass is defined with `weakref_slot=True` on Python >=3.11, the `__weakref__` attribute
+is generated. For now, we do not attempt to infer a more precise type for it.
+
+```toml
+[environment]
+python-version = "3.11"
+```
 
 ```py
 from dataclasses import dataclass
@@ -680,6 +685,58 @@ class C:
 reveal_type(C.__weakref__)  # revealed: Any | None
 ```
 
+The `__weakref__` attribute is correctly not modeled as existing on instances of slotted dataclasses
+where the class definition was not marked with `weakref=True`:
+
+```py
+from dataclasses import dataclass
+
+@dataclass(slots=True)
+class C: ...
+
+# error: [unresolved-attribute]
+reveal_type(C().__weakref__)  # revealed: Unknown
+```
+
+### New features are not available on old Python versions
+
+Certain parameters to `@dataclass` were added on newer Python versions; we do not infer them as
+having any effect on older Python versions:
+
+```toml
+[environment]
+python-version = "3.9"
+```
+
+```py
+from dataclasses import dataclass
+
+# fmt: off
+
+# TODO: these nonexistent keyword arguments should cause us to emit diagnostics on Python 3.9
+@dataclass(
+    slots=True,
+    weakref_slot=True,
+    match_args=True
+)
+class Foo: ...
+
+# fmt: on
+
+# error: [unresolved-attribute]
+reveal_type(Foo.__slots__)  # revealed: Unknown
+# error: [unresolved-attribute]
+reveal_type(Foo.__match_args__)  # revealed: Unknown
+
+# TODO: this actually *does* exist at runtime
+# (all classes and non-slotted instances have it available by default).
+# We could try to model that more fully...?
+# It's not added by the dataclasses machinery, though.
+#
+# error: [unresolved-attribute]
+reveal_type(Foo.__weakref__)  # revealed: Unknown
+```
+
 ## `Final` fields
 
 Dataclass fields can be annotated with `Final`, which means that the field cannot be reassigned

crates/ty_python_semantic/resources/mdtest/ide_support/all_members.md

@@ -682,7 +682,12 @@ static_assert(has_member(C(1), "__slots__"))
 
 #### `weakref_slot=True`
 
-When `weakref_slot=True`, the corresponding dunder attribute becomes available:
+When `weakref_slot=True` on Python >=3.11, the corresponding dunder attribute becomes available:
+
+```toml
+[environment]
+python-version = "3.11"
+```
 
 ```py
 from ty_extensions import has_member, static_assert
@@ -742,6 +747,32 @@ def _(c: C):
     static_assert(has_member(c, "__match_args__"))
 ```
 
+### Attributes added on new Python versions are not synthesized on older Python versions
+
+```toml
+[environment]
+python-version = "3.9"
+```
+
+```py
+from dataclasses import dataclass
+from ty_extensions import static_assert, has_member
+
+# TODO: these parameters don't exist on Python 3.9;
+# we should emit a diagnostic (or two)
+@dataclass(slots=True, weakref_slot=True)
+class F: ...
+
+static_assert(not has_member(F, "__slots__"))
+static_assert(not has_member(F, "__match_args__"))
+
+# In actual fact, all non-slotted instances have this attribute
+# (and even slotted instances can, if `__weakref__` is included in `__slots__`);
+# we could possibly model that more fully?
+# It's not added by the dataclasses machinery, though
+static_assert(not has_member(F(), "__weakref__"))
+```
+
 ### Attributes not available at runtime
 
 Typeshed includes some attributes in `object` that are not available for some (builtin) types. For

crates/ty_python_semantic/src/types/call/bind.rs

@@ -993,7 +993,11 @@ impl<'db> Bindings<'db> {
                                     flags |= DataclassFlags::FROZEN;
                                 }
                                 if to_bool(match_args, true) {
-                                    flags |= DataclassFlags::MATCH_ARGS;
+                                    if Program::get(db).python_version(db) >= PythonVersion::PY310 {
+                                        flags |= DataclassFlags::MATCH_ARGS;
+                                    } else {
+                                        // TODO: emit diagnostic
+                                    }
                                 }
                                 if to_bool(kw_only, false) {
                                     if Program::get(db).python_version(db) >= PythonVersion::PY310 {
@@ -1003,10 +1007,18 @@ impl<'db> Bindings<'db> {
                                     }
                                 }
                                 if to_bool(slots, false) {
-                                    flags |= DataclassFlags::SLOTS;
+                                    if Program::get(db).python_version(db) >= PythonVersion::PY310 {
+                                        flags |= DataclassFlags::SLOTS;
+                                    } else {
+                                        // TODO: emit diagnostic
+                                    }
                                 }
                                 if to_bool(weakref_slot, false) {
-                                    flags |= DataclassFlags::WEAKREF_SLOT;
+                                    if Program::get(db).python_version(db) >= PythonVersion::PY311 {
+                                        flags |= DataclassFlags::WEAKREF_SLOT;
+                                    } else {
+                                        // TODO: emit diagnostic
+                                    }
                                 }
 
                                 let params = DataclassParams::from_flags(db, flags);

crates/ty_python_semantic/src/types/class.rs

@@ -2397,7 +2397,9 @@ impl<'db> ClassLiteral<'db> {
                     .map(|(name, _)| Type::string_literal(db, name));
                 Some(Type::heterogeneous_tuple(db, match_args))
             }
-            (CodeGeneratorKind::DataclassLike(_), "__weakref__") => {
+            (CodeGeneratorKind::DataclassLike(_), "__weakref__")
+                if Program::get(db).python_version(db) >= PythonVersion::PY311 =>
+            {
                 if !has_dataclass_param(DataclassFlags::WEAKREF_SLOT)
                     || !has_dataclass_param(DataclassFlags::SLOTS)
                 {
@@ -2456,7 +2458,9 @@ impl<'db> ClassLiteral<'db> {
                 }
                 None
             }
-            (CodeGeneratorKind::DataclassLike(_), "__slots__") => {
+            (CodeGeneratorKind::DataclassLike(_), "__slots__")
+                if Program::get(db).python_version(db) >= PythonVersion::PY310 =>
+            {
                 has_dataclass_param(DataclassFlags::SLOTS).then(|| {
                     let fields = self.fields(db, specialization, field_policy);
                     let slots = fields.keys().map(|name| Type::string_literal(db, name));