Fix properties with setters after deleters (#19248)

Fixes #19224

Note we must add an additional attribute on `OverloadedFuncDef` since
decorator expressions are not serialized.

Author: ilevkivskyi

mypy/checker.py

@@ -675,11 +675,9 @@ def _visit_overloaded_func_def(self, defn: OverloadedFuncDef) -> None:
             assert isinstance(defn.items[0], Decorator)
             self.visit_decorator(defn.items[0])
             if defn.items[0].var.is_settable_property:
-                # TODO: here and elsewhere we assume setter immediately follows getter.
-                assert isinstance(defn.items[1], Decorator)
                 # Perform a reduced visit just to infer the actual setter type.
-                self.visit_decorator_inner(defn.items[1], skip_first_item=True)
-                setter_type = defn.items[1].var.type
+                self.visit_decorator_inner(defn.setter, skip_first_item=True)
+                setter_type = defn.setter.var.type
                 # Check if the setter can accept two positional arguments.
                 any_type = AnyType(TypeOfAny.special_form)
                 fallback_setter_type = CallableType(
@@ -690,7 +688,7 @@ def _visit_overloaded_func_def(self, defn: OverloadedFuncDef) -> None:
                     fallback=self.named_type("builtins.function"),
                 )
                 if setter_type and not is_subtype(setter_type, fallback_setter_type):
-                    self.fail("Invalid property setter signature", defn.items[1].func)
+                    self.fail("Invalid property setter signature", defn.setter.func)
                 setter_type = self.extract_callable_type(setter_type, defn)
                 if not isinstance(setter_type, CallableType) or len(setter_type.arg_types) != 2:
                     # TODO: keep precise type for callables with tricky but valid signatures.
@@ -2149,7 +2147,7 @@ def check_setter_type_override(self, defn: OverloadedFuncDef, base: TypeInfo) ->
         assert typ is not None and original_type is not None
 
         if not is_subtype(original_type, typ):
-            self.msg.incompatible_setter_override(defn.items[1], typ, original_type, base)
+            self.msg.incompatible_setter_override(defn.setter, typ, original_type, base)
 
     def check_method_override_for_base_with_name(
         self, defn: FuncDef | OverloadedFuncDef | Decorator, name: str, base: TypeInfo

mypy/checkmember.py

@@ -341,8 +341,8 @@ def analyze_instance_member_access(
             assert isinstance(method, OverloadedFuncDef)
             getter = method.items[0]
             assert isinstance(getter, Decorator)
-            if mx.is_lvalue and (len(items := method.items) > 1):
-                mx.chk.warn_deprecated(items[1], mx.context)
+            if mx.is_lvalue and getter.var.is_settable_property:
+                mx.chk.warn_deprecated(method.setter, mx.context)
             return analyze_var(name, getter.var, typ, mx)
 
         if mx.is_lvalue and not mx.suppress_errors:

mypy/nodes.py

@@ -550,19 +550,28 @@ class OverloadedFuncDef(FuncBase, SymbolNode, Statement):
     Overloaded variants must be consecutive in the source file.
     """
 
-    __slots__ = ("items", "unanalyzed_items", "impl", "deprecated", "_is_trivial_self")
+    __slots__ = (
+        "items",
+        "unanalyzed_items",
+        "impl",
+        "deprecated",
+        "setter_index",
+        "_is_trivial_self",
+    )
 
     items: list[OverloadPart]
     unanalyzed_items: list[OverloadPart]
     impl: OverloadPart | None
     deprecated: str | None
+    setter_index: int | None
 
     def __init__(self, items: list[OverloadPart]) -> None:
         super().__init__()
         self.items = items
         self.unanalyzed_items = items.copy()
         self.impl = None
         self.deprecated = None
+        self.setter_index = None
         self._is_trivial_self: bool | None = None
         if items:
             # TODO: figure out how to reliably set end position (we don't know the impl here).
@@ -598,6 +607,17 @@ def is_trivial_self(self) -> bool:
         self._is_trivial_self = True
         return True
 
+    @property
+    def setter(self) -> Decorator:
+        # Do some consistency checks first.
+        first_item = self.items[0]
+        assert isinstance(first_item, Decorator)
+        assert first_item.var.is_settable_property
+        assert self.setter_index is not None
+        item = self.items[self.setter_index]
+        assert isinstance(item, Decorator)
+        return item
+
     def accept(self, visitor: StatementVisitor[T]) -> T:
         return visitor.visit_overloaded_func_def(self)
 
@@ -610,6 +630,7 @@ def serialize(self) -> JsonDict:
             "impl": None if self.impl is None else self.impl.serialize(),
             "flags": get_flags(self, FUNCBASE_FLAGS),
             "deprecated": self.deprecated,
+            "setter_index": self.setter_index,
         }
 
     @classmethod
@@ -630,6 +651,7 @@ def deserialize(cls, data: JsonDict) -> OverloadedFuncDef:
         res._fullname = data["fullname"]
         set_flags(res, data["flags"])
         res.deprecated = data["deprecated"]
+        res.setter_index = data["setter_index"]
         # NOTE: res.info will be set in the fixup phase.
         return res
 

mypy/semanal.py

@@ -1558,6 +1558,7 @@ def analyze_property_with_multi_part_definition(
                             )
                             assert isinstance(setter_func_type, CallableType)
                             bare_setter_type = setter_func_type
+                            defn.setter_index = i + 1
                         if first_node.name == "deleter":
                             item.func.abstract_status = first_item.func.abstract_status
                         for other_node in item.decorators[1:]:

test-data/unit/check-classes.test

@@ -8739,3 +8739,23 @@ class NoopPowerResource:
     def hardware_type(self) -> None:  # E: Invalid property setter signature
         self.hardware_type = None  # Note: intentionally recursive
 [builtins fixtures/property.pyi]
+
+[case testPropertyAllowsDeleterBeforeSetter]
+class C:
+    @property
+    def foo(self) -> str: ...
+    @foo.deleter
+    def foo(self) -> None: ...
+    @foo.setter
+    def foo(self, val: int) -> None: ...
+
+    @property
+    def bar(self) -> int: ...
+    @bar.deleter
+    def bar(self) -> None: ...
+    @bar.setter
+    def bar(self, value: int, val: int) -> None: ...  # E: Invalid property setter signature
+
+C().foo = "no"  # E: Incompatible types in assignment (expression has type "str", variable has type "int")
+C().bar = "fine"
+[builtins fixtures/property.pyi]