Do not use dictionary in CallableType

Author: ilevkivskyi

mypy/fixup.py

@@ -29,6 +29,7 @@
     Overloaded,
     Parameters,
     ParamSpecType,
+    ProperType,
     TupleType,
     TypeAliasType,
     TypedDictType,
@@ -177,6 +178,11 @@ def visit_overloaded_func_def(self, o: OverloadedFuncDef) -> None:
             item.accept(self)
         if o.impl:
             o.impl.accept(self)
+        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
 
     def visit_decorator(self, d: Decorator) -> None:
         if self.current_info is not None:
@@ -187,6 +193,8 @@ 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
 
     def visit_class_def(self, c: ClassDef) -> None:
         for v in c.type_vars:

mypy/messages.py

@@ -1003,7 +1003,7 @@ def maybe_note_about_special_args(self, callee: CallableType, context: Context)
         if self.prefer_simple_messages():
             return
         # https://github.com/python/mypy/issues/11309
-        first_arg = callee.def_extras.get("first_arg")
+        first_arg = get_first_arg(callee)
         if first_arg and first_arg not in {"self", "cls", "mcs"}:
             self.note(
                 "Looks like the first special argument in a method "
@@ -3007,7 +3007,7 @@ def [T <: int] f(self, x: int, y: T) -> None
             s = definition_arg_names[0] + s
         s = f"{tp.definition.name}({s})"
     elif tp.name:
-        first_arg = tp.def_extras.get("first_arg")
+        first_arg = get_first_arg(tp)
         if first_arg:
             if s:
                 s = ", " + s
@@ -3050,6 +3050,12 @@ def [T <: int] f(self, x: int, y: T) -> None
     return f"def {s}"
 
 
+def get_first_arg(tp: CallableType) -> str | None:
+    if not isinstance(tp.definition, FuncDef) or not tp.definition.info or tp.definition.is_static:
+        return None
+    return tp.definition.original_first_arg
+
+
 def variance_string(variance: int) -> str:
     if variance == COVARIANT:
         return "covariant"

mypy/nodes.py

@@ -823,6 +823,7 @@ class FuncDef(FuncItem, SymbolNode, Statement):
         "dataclass_transform_spec",
         "docstring",
         "deprecated",
+        "original_first_arg",
     )
 
     __match_args__ = ("name", "arguments", "type", "body")
@@ -855,6 +856,12 @@ def __init__(
         # the majority). In cases where self is not annotated and there are no Self
         # in the signature we can simply drop the first argument.
         self.is_trivial_self = False
+        # This is needed because for positional-only arguments the name is set to None,
+        # but we sometimes still want to show it in error messages.
+        if arguments:
+            self.original_first_arg: str | None = arguments[0].variable.name
+        else:
+            self.original_first_arg = None
 
     @property
     def name(self) -> str:
@@ -886,6 +893,7 @@ def serialize(self) -> JsonDict:
                 else self.dataclass_transform_spec.serialize()
             ),
             "deprecated": self.deprecated,
+            "original_first_arg": self.original_first_arg,
         }
 
     @classmethod
@@ -906,6 +914,7 @@ def deserialize(cls, data: JsonDict) -> FuncDef:
         set_flags(ret, data["flags"])
         # NOTE: ret.info is set in the fixup phase.
         ret.arg_names = data["arg_names"]
+        ret.original_first_arg = data.get("original_first_arg")
         ret.arg_kinds = [ArgKind(x) for x in data["arg_kinds"]]
         ret.abstract_status = data["abstract_status"]
         ret.dataclass_transform_spec = (

mypy/types.py

@@ -21,16 +21,7 @@
 
 import mypy.nodes
 from mypy.bogus_type import Bogus
-from mypy.nodes import (
-    ARG_POS,
-    ARG_STAR,
-    ARG_STAR2,
-    INVARIANT,
-    ArgKind,
-    FakeInfo,
-    FuncDef,
-    SymbolNode,
-)
+from mypy.nodes import ARG_POS, ARG_STAR, ARG_STAR2, INVARIANT, ArgKind, FakeInfo, SymbolNode
 from mypy.options import Options
 from mypy.state import state
 from mypy.util import IdMapper
@@ -1841,8 +1832,6 @@ class CallableType(FunctionLike):
         "from_type_type",  # Was this callable generated by analyzing Type[...]
         # instantiation?
         "is_bound",  # Is this a bound method?
-        "def_extras",  # Information about original definition we want to serialize.
-        # This is used for more detailed error messages.
         "type_guard",  # T, if -> TypeGuard[T] (ret_type is bool in this case).
         "type_is",  # T, if -> TypeIs[T] (ret_type is bool in this case).
         "from_concatenate",  # whether this callable is from a concatenate object
@@ -1869,7 +1858,6 @@ def __init__(
         special_sig: str | None = None,
         from_type_type: bool = False,
         is_bound: bool = False,
-        def_extras: dict[str, Any] | None = None,
         type_guard: Type | None = None,
         type_is: Type | None = None,
         from_concatenate: bool = False,
@@ -1902,22 +1890,6 @@ def __init__(
         self.from_concatenate = from_concatenate
         self.imprecise_arg_kinds = imprecise_arg_kinds
         self.is_bound = is_bound
-        if def_extras:
-            self.def_extras = def_extras
-        elif isinstance(definition, FuncDef):
-            # This information would be lost if we don't have definition
-            # after serialization, but it is useful in error messages.
-            # TODO: decide how to add more info here (file, line, column)
-            # without changing interface hash.
-            first_arg: str | None = None
-            if definition.arg_names and definition.info and not definition.is_static:
-                if getattr(definition, "arguments", None):
-                    first_arg = definition.arguments[0].variable.name
-                else:
-                    first_arg = definition.arg_names[0]
-            self.def_extras = {"first_arg": first_arg}
-        else:
-            self.def_extras = {}
         self.type_guard = type_guard
         self.type_is = type_is
         self.unpack_kwargs = unpack_kwargs
@@ -1939,7 +1911,6 @@ def copy_modified(
         special_sig: Bogus[str | None] = _dummy,
         from_type_type: Bogus[bool] = _dummy,
         is_bound: Bogus[bool] = _dummy,
-        def_extras: Bogus[dict[str, Any]] = _dummy,
         type_guard: Bogus[Type | None] = _dummy,
         type_is: Bogus[Type | None] = _dummy,
         from_concatenate: Bogus[bool] = _dummy,
@@ -1964,7 +1935,6 @@ def copy_modified(
             special_sig=special_sig if special_sig is not _dummy else self.special_sig,
             from_type_type=from_type_type if from_type_type is not _dummy else self.from_type_type,
             is_bound=is_bound if is_bound is not _dummy else self.is_bound,
-            def_extras=def_extras if def_extras is not _dummy else dict(self.def_extras),
             type_guard=type_guard if type_guard is not _dummy else self.type_guard,
             type_is=type_is if type_is is not _dummy else self.type_is,
             from_concatenate=(
@@ -2291,7 +2261,6 @@ def serialize(self) -> JsonDict:
             "is_ellipsis_args": self.is_ellipsis_args,
             "implicit": self.implicit,
             "is_bound": self.is_bound,
-            "def_extras": dict(self.def_extras),
             "type_guard": self.type_guard.serialize() if self.type_guard is not None else None,
             "type_is": (self.type_is.serialize() if self.type_is is not None else None),
             "from_concatenate": self.from_concatenate,
@@ -2314,7 +2283,6 @@ def deserialize(cls, data: JsonDict) -> CallableType:
             is_ellipsis_args=data["is_ellipsis_args"],
             implicit=data["implicit"],
             is_bound=data["is_bound"],
-            def_extras=data["def_extras"],
             type_guard=(
                 deserialize_type(data["type_guard"]) if data["type_guard"] is not None else None
             ),

test-data/unit/check-serialize.test

@@ -224,6 +224,7 @@ def f(x: int) -> int: pass
 [out2]
 tmp/a.py:2: note: Revealed type is "builtins.str"
 tmp/a.py:3: error: Unexpected keyword argument "x" for "f"
+tmp/b.py: note: "f" defined here
 
 [case testSerializeTypeGuardFunction]
 import a