Fix crash on settable property alias

mypy/checker.py

@@ -703,6 +703,12 @@ def _visit_overloaded_func_def(self, defn: OverloadedFuncDef) -> None:
                     # TODO: keep precise type for callables with tricky but valid signatures.
                     setter_type = fallback_setter_type
                 defn.items[0].var.setter_type = setter_type
+                if isinstance(defn.type, Overloaded):
+                    # Update legacy property type for decorated properties.
+                    getter_type = self.extract_callable_type(defn.items[0].var.type, defn)
+                    if getter_type is not None:
+                        getter_type.definition = defn.items[0]
+                        defn.type.items[0] = getter_type
         for i, fdef in enumerate(defn.items):
             assert isinstance(fdef, Decorator)
             if defn.is_property:
@@ -730,7 +736,7 @@ def _visit_overloaded_func_def(self, defn: OverloadedFuncDef) -> None:
                     assert isinstance(item, Decorator)
                     item_type = self.extract_callable_type(item.var.type, item)
                     if item_type is not None:
-                        item_type.definition = item.func
+                        item_type.definition = item
                         item_types.append(item_type)
                 if item_types:
                     defn.type = Overloaded(item_types)
@@ -3509,6 +3515,7 @@ def check_compatibility_all_supers(self, lvalue: RefExpr, rvalue: Expression) ->
                     continue
 
                 base_type, base_node = self.node_type_from_base(lvalue_node.name, base, lvalue)
+                # TODO: if the r.h.s. is a descriptor, we should check setter override as well.
                 custom_setter = is_custom_settable_property(base_node)
                 if isinstance(base_type, PartialType):
                     base_type = None
@@ -4494,6 +4501,8 @@ def set_inferred_type(self, var: Var, lvalue: Lvalue, type: Type) -> None:
                     if isinstance(p_type, Overloaded):
                         # TODO: in theory we can have a property with a deleter only.
                         var.is_settable_property = True
+                        assert isinstance(definition, Decorator)
+                        var.setter_type = definition.var.setter_type
 
     def set_inference_error_fallback_type(self, var: Var, lvalue: Lvalue, type: Type) -> None:
         """Store best known type for variable if type inference failed.
@@ -5356,6 +5365,8 @@ def visit_decorator_inner(
             self.check_untyped_after_decorator(sig, e.func)
         self.require_correct_self_argument(sig, e.func)
         sig = set_callable_name(sig, e.func)
+        if isinstance(sig, CallableType):
+            sig.definition = e
         e.var.type = sig
         e.var.is_ready = True
         if e.func.is_property:
@@ -8651,17 +8662,21 @@ def visit_type_alias_type(self, t: TypeAliasType) -> Type:
         return t.copy_modified(args=[a.accept(self) for a in t.args])
 
 
-def is_classmethod_node(node: Node | None) -> bool | None:
+def is_classmethod_node(node: SymbolNode | None) -> bool | None:
     """Find out if a node describes a classmethod."""
+    if isinstance(node, Decorator):
+        node = node.func
     if isinstance(node, FuncDef):
         return node.is_class
     if isinstance(node, Var):
         return node.is_classmethod
     return None
 
 
-def is_node_static(node: Node | None) -> bool | None:
+def is_node_static(node: SymbolNode | None) -> bool | None:
     """Find out if a node describes a static function method."""
+    if isinstance(node, Decorator):
+        node = node.func
     if isinstance(node, FuncDef):
         return node.is_static
     if isinstance(node, Var):

mypy/checkmember.py

@@ -976,7 +976,14 @@ def expand_and_bind_callable(
     freeze_all_type_vars(expanded)
     if not var.is_property:
         return expanded
-    # TODO: a decorated property can result in Overloaded here.
+    if isinstance(expanded, Overloaded):
+        # Legacy way to store settable properties is with overloads. Also in case it is
+        # an actual overloaded property, selecting first item that passed check_self_arg()
+        # is a good approximation, long-term we should use check_call() inference below.
+        if not expanded.items:
+            # A broken overload, error should be already reported.
+            return AnyType(TypeOfAny.from_error)
+        expanded = expanded.items[0]
     assert isinstance(expanded, CallableType)
     if var.is_settable_property and mx.is_lvalue and var.setter_type is not None:
         if expanded.variables:

mypy/fixup.py

@@ -181,8 +181,7 @@ def visit_overloaded_func_def(self, o: OverloadedFuncDef) -> None:
         if isinstance(o.type, Overloaded):
             # For error messages we link the original definition for each item.
             for typ, item in zip(o.type.items, o.items):
-                if isinstance(item, Decorator):
-                    typ.definition = item.func
+                typ.definition = item
 
     def visit_decorator(self, d: Decorator) -> None:
         if self.current_info is not None:
@@ -193,8 +192,9 @@ def visit_decorator(self, d: Decorator) -> None:
             d.var.accept(self)
         for node in d.decorators:
             node.accept(self)
-        if isinstance(d.var.type, ProperType) and isinstance(d.var.type, CallableType):
-            d.var.type.definition = d.func
+        typ = d.var.type
+        if isinstance(typ, ProperType) and isinstance(typ, CallableType):
+            typ.definition = d.func
 
     def visit_class_def(self, c: ClassDef) -> None:
         for v in c.type_vars:

mypy/messages.py

@@ -44,6 +44,7 @@
     CallExpr,
     ClassDef,
     Context,
+    Decorator,
     Expression,
     FuncDef,
     IndexExpr,
@@ -2938,10 +2939,13 @@ def format_single(arg: Type) -> str:
 
 def pretty_class_or_static_decorator(tp: CallableType) -> str | None:
     """Return @classmethod or @staticmethod, if any, for the given callable type."""
-    if tp.definition is not None and isinstance(tp.definition, SYMBOL_FUNCBASE_TYPES):
-        if tp.definition.is_class:
+    definition = tp.definition
+    if isinstance(definition, Decorator):
+        definition = definition.func
+    if definition is not None and isinstance(definition, SYMBOL_FUNCBASE_TYPES):
+        if definition.is_class:
             return "@classmethod"
-        if tp.definition.is_static:
+        if definition.is_static:
             return "@staticmethod"
     return None
 
@@ -2991,12 +2995,15 @@ def [T <: int] f(self, x: int, y: T) -> None
             slash = True
 
     # If we got a "special arg" (i.e: self, cls, etc...), prepend it to the arg list
+    definition = tp.definition
+    if isinstance(definition, Decorator):
+        definition = definition.func
     if (
-        isinstance(tp.definition, FuncDef)
-        and hasattr(tp.definition, "arguments")
+        isinstance(definition, FuncDef)
+        and hasattr(definition, "arguments")
         and not tp.from_concatenate
     ):
-        definition_arg_names = [arg.variable.name for arg in tp.definition.arguments]
+        definition_arg_names = [arg.variable.name for arg in definition.arguments]
         if (
             len(definition_arg_names) > len(tp.arg_names)
             and definition_arg_names[0]
@@ -3005,7 +3012,7 @@ def [T <: int] f(self, x: int, y: T) -> None
             if s:
                 s = ", " + s
             s = definition_arg_names[0] + s
-        s = f"{tp.definition.name}({s})"
+        s = f"{definition.name}({s})"
     elif tp.name:
         first_arg = get_first_arg(tp)
         if first_arg:
@@ -3051,9 +3058,12 @@ def [T <: int] f(self, x: int, y: T) -> None
 
 
 def get_first_arg(tp: CallableType) -> str | None:
-    if not isinstance(tp.definition, FuncDef) or not tp.definition.info or tp.definition.is_static:
+    definition = tp.definition
+    if isinstance(definition, Decorator):
+        definition = definition.func
+    if not isinstance(definition, FuncDef) or not definition.info or definition.is_static:
         return None
-    return tp.definition.original_first_arg
+    return definition.original_first_arg
 
 
 def variance_string(variance: int) -> str:

mypy/semanal.py

@@ -1243,6 +1243,7 @@ def analyze_overloaded_func_def(self, defn: OverloadedFuncDef) -> None:
             bare_setter_type = self.analyze_property_with_multi_part_definition(defn)
             typ = function_type(first_item.func, self.named_type("builtins.function"))
             assert isinstance(typ, CallableType)
+            typ.definition = first_item
             types = [typ]
         else:
             # This is a normal overload. Find the item signatures, the
@@ -1374,6 +1375,7 @@ def analyze_overload_sigs_and_impl(
             if isinstance(item, Decorator):
                 callable = function_type(item.func, self.named_type("builtins.function"))
                 assert isinstance(callable, CallableType)
+                callable.definition = item
                 if not any(refers_to_fullname(dec, OVERLOAD_NAMES) for dec in item.decorators):
                     if i == len(defn.items) - 1 and not self.is_stub_file:
                         # Last item outside a stub is impl

mypy/types.py

@@ -1887,6 +1887,9 @@ def __init__(
         self.fallback = fallback
         assert not name or "<bound method" not in name
         self.name = name
+        # The rules for what exactly is considered a definition:
+        #   * If it is a non-decorated function, FuncDef is the definition
+        #   * If it is a decorated function, enclosing Decorator is the definition
         self.definition = definition
         self.variables = variables
         self.is_ellipsis_args = is_ellipsis_args

test-data/unit/check-classes.test

@@ -9211,3 +9211,33 @@ class CGT(BG[T]): ...
 
 reveal_type(CGI)  # N: Revealed type is "def () -> __main__.CGI"
 reveal_type(CGT)  # N: Revealed type is "def [T] () -> __main__.CGT[T`1]"
+
+[case testSettablePropertyAlias]
+from typing import Any, TypeVar
+
+class A:
+    @property
+    def prop(self: Any) -> str: ...
+    @prop.setter
+    def prop(self, val: str) -> None: ...
+
+T = TypeVar("T")
+class AT:
+    @property
+    def prop(self: T) -> T: ...
+    @prop.setter
+    def prop(self: T, val: list[T]) -> None: ...
+
+class B:
+    prop: str
+    prop_t: str
+
+class C(B):
+    prop = A.prop
+    prop_t = AT.prop  # E: Incompatible types in assignment (expression has type "C", base class "B" defined the type as "str")
+
+reveal_type(C().prop)  # N: Revealed type is "builtins.str"
+C().prop = "no"  # E: Invalid self argument "C" to attribute function "prop" with type "Callable[[A, str], None]"
+reveal_type(C().prop_t)  # N: Revealed type is "__main__.C"
+C().prop_t = 1  # E: Incompatible types in assignment (expression has type "int", variable has type "list[C]")
+[builtins fixtures/property.pyi]

test-data/unit/check-dataclasses.test

@@ -2055,7 +2055,7 @@ from dataclasses import dataclass, replace, InitVar
 from typing import ClassVar
 
 @dataclass
-class A:
+class A:  # N: "replace" of "A" defined here
     x: int
     q: InitVar[int]
     q2: InitVar[int] = 0

test-data/unit/fine-grained.test

@@ -7312,9 +7312,7 @@ class C:
 ==
 mod.py:9: error: Incompatible types in assignment (expression has type "int", variable has type "str")
 
-[case testOverloadedMethodSupertype-only_when_cache]
--- Different cache/no-cache tests because
--- CallableType.def_extras.first_arg differs ("self"/None)
+[case testOverloadedMethodSupertype]
 from typing import overload, Any
 import b
 class Child(b.Parent):
@@ -7355,49 +7353,6 @@ main:4: note:          def f(self, arg: int) -> int
 main:4: note:          @overload
 main:4: note:          def f(self, arg: str) -> str
 
-[case testOverloadedMethodSupertype2-only_when_nocache]
--- Different cache/no-cache tests because
--- CallableType.def_extras.first_arg differs ("self"/None)
-from typing import overload, Any
-import b
-class Child(b.Parent):
-    @overload                           # Fail
-    def f(self, arg: int) -> int: ...
-    @overload
-    def f(self, arg: str) -> str: ...
-    def f(self, arg: Any) -> Any: ...
-[file b.py]
-from typing import overload, Any
-class C: pass
-class Parent:
-    @overload
-    def f(self, arg: int) -> int: ...
-    @overload
-    def f(self, arg: str) -> str: ...
-    def f(self, arg: Any) -> Any: ...
-[file b.py.2]
-from typing import overload, Any
-class C: pass
-class Parent:
-    @overload
-    def f(self, arg: int) -> int: ...
-    @overload
-    def f(self, arg: str) -> C: ...
-    def f(self, arg: Any) -> Any: ...
-[out]
-==
-main:4: error: Signature of "f" incompatible with supertype "b.Parent"
-main:4: note:      Superclass:
-main:4: note:          @overload
-main:4: note:          def f(self, arg: int) -> int
-main:4: note:          @overload
-main:4: note:          def f(self, arg: str) -> C
-main:4: note:      Subclass:
-main:4: note:          @overload
-main:4: note:          def f(arg: int) -> int
-main:4: note:          @overload
-main:4: note:          def f(arg: str) -> str
-
 [case testOverloadedInitSupertype]
 import a
 [file a.py]
@@ -8486,9 +8441,7 @@ class D:
 ==
 a.py:3: error: Cannot override final attribute "meth" (previously declared in base class "C")
 
-[case testFinalBodyReprocessedAndStillFinalOverloaded-only_when_cache]
--- Different cache/no-cache tests because
--- CallableType.def_extras.first_arg differs ("self"/None)
+[case testFinalBodyReprocessedAndStillFinalOverloaded]
 import a
 [file a.py]
 from c import C
@@ -8533,53 +8486,6 @@ a.py:3: note:          def meth(self, x: str) -> str
 a.py:3: note:      Subclass:
 a.py:3: note:          def meth(self) -> None
 
-[case testFinalBodyReprocessedAndStillFinalOverloaded2-only_when_nocache]
--- Different cache/no-cache tests because
--- CallableType.def_extras.first_arg differs ("self"/None)
-import a
-[file a.py]
-from c import C
-class A:
-    def meth(self) -> None: ...
-
-[file a.py.3]
-from c import C
-class A(C):
-    def meth(self) -> None: ...
-
-[file c.py]
-from typing import final, overload, Union
-from d import D
-
-class C:
-    @overload
-    def meth(self, x: int) -> int: ...
-    @overload
-    def meth(self, x: str) -> str: ...
-    @final
-    def meth(self, x: Union[int, str]) -> Union[int, str]:
-        D(int())
-        return x
-[file d.py]
-class D:
-    def __init__(self, x: int) -> None: ...
-[file d.py.2]
-from typing import Optional
-class D:
-    def __init__(self, x: Optional[int]) -> None: ...
-[out]
-==
-==
-a.py:3: error: Cannot override final attribute "meth" (previously declared in base class "C")
-a.py:3: error: Signature of "meth" incompatible with supertype "c.C"
-a.py:3: note:      Superclass:
-a.py:3: note:          @overload
-a.py:3: note:          def meth(x: int) -> int
-a.py:3: note:          @overload
-a.py:3: note:          def meth(x: str) -> str
-a.py:3: note:      Subclass:
-a.py:3: note:          def meth(self) -> None
-
 [case testIfMypyUnreachableClass]
 from a import x
 

test-data/unit/pythoneval.test

@@ -1970,6 +1970,7 @@ a2 = replace()
 a2 = replace(a, x='spam')
 a2 = replace(a, x=42, q=42)
 [out]
+_testDataclassReplace.py:4: note: "replace" of "A" defined here
 _testDataclassReplace.py:9: note: Revealed type is "_testDataclassReplace.A"
 _testDataclassReplace.py:10: error: Too few arguments for "replace"
 _testDataclassReplace.py:11: error: Argument "x" to "replace" of "A" has incompatible type "str"; expected "int"