Add more error checking

python · JukkaL · Apr 5, 2023 · Apr 4, 2023 · Apr 4, 2023 · Apr 4, 2023
commit 9ff3c6ce2a4d6a471d11ce6ab0729af2ce02a36f
diff --git a/mypy/plugins/dataclasses.py b/mypy/plugins/dataclasses.py
@@ -582,7 +582,7 @@ def collect_attributes(self) -> list[DataclassAttribute] | None:
                     )
 
             current_attr_names.add(lhs.name)
-            init_type = _infer_dataclass_attr_init_type(sym)
+            init_type = self._infer_dataclass_attr_init_type(sym, lhs.name)
             found_attrs[lhs.name] = DataclassAttribute(
                name=lhs.name,
                 alias=alias,
@@ -760,6 +760,36 @@ def _get_bool_arg(self, name: str, default: bool) -> bool:
             return require_bool_literal_argument(self._api, expression, name, default)
         return default
 
+    def _infer_dataclass_attr_init_type(self, sym: SymbolTableNode, name: str) -> Type | None:
+        """Infer __init__ argument type for an attribute.
+
+        In particular, possibly use the signature of __set__.
+        """
+        default = sym.type
+        if sym.implicit:
+            return default
+        t = get_proper_type(sym.type)
+        if not isinstance(t, Instance):
+            return default
+        if "__set__" in t.type.names:
+            setter = t.type.names["__set__"]
+            if isinstance(setter.node, FuncDef):
+                setter_type = get_proper_type(setter.type)
+                if isinstance(setter_type, CallableType) and setter_type.arg_kinds == [
+                    ARG_POS,
+                    ARG_POS,
+                    ARG_POS,
+                ]:
+                    return expand_type_by_instance(setter_type.arg_types[2], t)
+                else:
+                    self._api.fail(
+                        f'Unsupported signature for "__set__" in "{t.type.name}"', sym.node
+                    )
+            else:
+                self._api.fail(f'Unsupported "__set__" in "{t.type.name}"', sym.node)
+
+        return default
+
 
 def add_dataclass_tag(info: TypeInfo) -> None:
     # The value is ignored, only the existence matters.
@@ -816,20 +846,3 @@ def _has_direct_dataclass_transform_metaclass(info: TypeInfo) -> bool:
         info.declared_metaclass is not None
         and info.declared_metaclass.type.dataclass_transform_spec is not None
     )
-
-
-def _infer_dataclass_attr_init_type(sym: SymbolTableNode) -> Type | None:
-    if sym.implicit:
-        return sym.type
-    t = get_proper_type(sym.type)
-    if not isinstance(t, Instance):
-        return sym.type
-    if "__set__" in t.type.names:
-        n = t.type.names["__set__"]
-        if isinstance(n.node, FuncDef):
-            setter_type = get_proper_type(n.type)
-            if not isinstance(setter_type, CallableType):
-                assert False, "unknown type"
-            if setter_type.arg_kinds == [ARG_POS, ARG_POS, ARG_POS]:
-                return expand_type_by_instance(setter_type.arg_types[2], t)
-    return sym.type
diff --git a/test-data/unit/check-dataclass-transform.test b/test-data/unit/check-dataclass-transform.test
@@ -919,3 +919,40 @@ c.x = 1  # E: Incompatible types in assignment (expression has type "int", varia
 
 [typing fixtures/typing-full.pyi]
 [builtins fixtures/dataclasses.pyi]
+
+[case testDataclassTransformUnsupportedDescriptors]
+# flags: --python-version 3.11
+
+from typing import dataclass_transform, overload, Any
+
+@dataclass_transform()
+def my_dataclass(cls): ...
+
+class Desc:
+    @overload
+    def __get__(self, instance: None, owner: Any) -> int: ...
+    @overload
+    def __get__(self, instance: object, owner: Any) -> str: ...
+    def __get__(self, instance, owner): ...
+
+    def __set__(*args, **kwargs): ...
+
+class Desc2:
+    @overload
+    def __get__(self, instance: None, owner: Any) -> int: ...
+    @overload
+    def __get__(self, instance: object, owner: Any) -> str: ...
+    def __get__(self, instance, owner): ...
+
+    @overload
+    def __set__(self, instance: Any, value: bytes) -> None: ...
+    @overload
+    def __set__(self) -> None: ...
+    def __set__(self, *args, **kawrga) -> None: ...
+
+@my_dataclass
+class C:
+    x: Desc  # E: Unsupported signature for "__set__" in "Desc"
+    y: Desc2  # E: Unsupported "__set__" in "Desc2"
+[typing fixtures/typing-full.pyi]
+[builtins fixtures/dataclasses.pyi]