[ty] Treat functions, methods, and dynamic types as function-like Callables (#20842)

## Summary

Treat functions, methods, and dynamic types as function-like `Callable`s

closes https://github.com/astral-sh/ty/issues/1342
closes https://github.com/astral-sh/ty/issues/1344

## Ecosystem analysis

All removed diagnostics look like cases of
https://github.com/astral-sh/ty/issues/1344

## Test Plan

Added regression test

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

@@ -1204,9 +1204,9 @@ python-version = "3.12"
 from dataclasses import dataclass
 from typing import Callable
 from types import FunctionType
-from ty_extensions import CallableTypeOf, TypeOf, static_assert, is_subtype_of, is_assignable_to
+from ty_extensions import CallableTypeOf, TypeOf, static_assert, is_subtype_of, is_assignable_to, is_equivalent_to
 
-@dataclass
+@dataclass(order=True)
 class C:
     x: int
 
@@ -1233,8 +1233,20 @@ static_assert(not is_assignable_to(EquivalentPureCallableType, DunderInitType))
 static_assert(is_subtype_of(DunderInitType, EquivalentFunctionLikeCallableType))
 static_assert(is_assignable_to(DunderInitType, EquivalentFunctionLikeCallableType))
 
-static_assert(not is_subtype_of(EquivalentFunctionLikeCallableType, DunderInitType))
+static_assert(is_subtype_of(EquivalentFunctionLikeCallableType, DunderInitType))
-static_assert(not is_assignable_to(EquivalentFunctionLikeCallableType, DunderInitType))
+static_assert(is_assignable_to(EquivalentFunctionLikeCallableType, DunderInitType))
+
+static_assert(is_equivalent_to(EquivalentFunctionLikeCallableType, DunderInitType))
 
 static_assert(is_subtype_of(DunderInitType, FunctionType))
 ```
+
+It should be possible to mock out synthesized methods:
+
+```py
+from unittest.mock import Mock
+
+def test_c():
+    c = C(1)
+    c.__lt__ = Mock()
+```

crates/ty_python_semantic/resources/mdtest/literal/collections/list.md

@@ -25,6 +25,12 @@ x = [a, b]
 reveal_type(x)  # revealed: list[Unknown | ((_: int) -> int)]
 ```
 
+The inferred `Callable` type is function-like, i.e. we can still access attributes like `__name__`:
+
+```py
+reveal_type(x[0].__name__)  # revealed: Unknown | str
+```
+
 ## Mixed list
 
 ```py

crates/ty_python_semantic/resources/mdtest/type_properties/is_assignable_to.md

@@ -963,6 +963,40 @@ c: Callable[[Any], str] = f
 c: Callable[[Any], str] = g
 ```
 
+A function with no explicit return type should be assignable to a callable with a return type of
+`Any`.
+
+```py
+def h():
+    return
+
+c: Callable[[], Any] = h
+```
+
+And, similarly for parameters with no annotations:
+
+```py
+def i(a, b, /) -> None:
+    return
+
+c: Callable[[Any, Any], None] = i
+```
+
+Additionally, a function definition that includes both `*args` and `**kwargs` parameters that are
+annotated as `Any` or kept unannotated should be assignable to a callable with `...` as the
+parameter type.
+
+```py
+def variadic_without_annotation(*args, **kwargs):
+    return
+
+def variadic_with_annotation(*args: Any, **kwargs: Any) -> Any:
+    return
+
+c: Callable[..., Any] = variadic_without_annotation
+c: Callable[..., Any] = variadic_with_annotation
+```
+
 ### Method types
 
 ```py

crates/ty_python_semantic/resources/mdtest/type_properties/is_equivalent_to.md

@@ -464,7 +464,7 @@ gradual types. The cases with fully static types and using different combination
 are covered above.
 
 ```py
-from ty_extensions import Unknown, CallableTypeOf, is_equivalent_to, static_assert
+from ty_extensions import Unknown, CallableTypeOf, TypeOf, is_equivalent_to, static_assert
 from typing import Any, Callable
 
 static_assert(is_equivalent_to(Callable[..., int], Callable[..., int]))
@@ -476,14 +476,17 @@ static_assert(not is_equivalent_to(Callable[[int, str], None], Callable[[int, st
 static_assert(not is_equivalent_to(Callable[..., None], Callable[[], None]))
 ```
 
-A function with no explicit return type should be gradual equivalent to a callable with a return
+A function with no explicit return type should be gradually equivalent to a function-like callable
-type of `Any`.
+with a return type of `Any`.
 
 ```py
 def f1():
     return
 
-static_assert(is_equivalent_to(CallableTypeOf[f1], Callable[[], Any]))
+def f1_equivalent() -> Any:
+    return
+
+static_assert(is_equivalent_to(CallableTypeOf[f1], CallableTypeOf[f1_equivalent]))
 ```
 
 And, similarly for parameters with no annotations.
@@ -492,12 +495,15 @@ And, similarly for parameters with no annotations.
 def f2(a, b, /) -> None:
     return
 
-static_assert(is_equivalent_to(CallableTypeOf[f2], Callable[[Any, Any], None]))
+def f2_equivalent(a: Any, b: Any, /) -> None:
+    return
+
+static_assert(is_equivalent_to(CallableTypeOf[f2], CallableTypeOf[f2_equivalent]))
 ```
 
-Additionally, as per the spec, a function definition that includes both `*args` and `**kwargs`
+A function definition that includes both `*args` and `**kwargs` parameter that are annotated as
-parameter that are annotated as `Any` or kept unannotated should be gradual equivalent to a callable
+`Any` or kept unannotated should be gradual equivalent to a callable with `...` as the parameter
-with `...` as the parameter type.
+type.
 
 ```py
 def variadic_without_annotation(*args, **kwargs):
@@ -506,12 +512,27 @@ def variadic_without_annotation(*args, **kwargs):
 def variadic_with_annotation(*args: Any, **kwargs: Any) -> Any:
     return
 
-static_assert(is_equivalent_to(CallableTypeOf[variadic_without_annotation], Callable[..., Any]))
+def _(
-static_assert(is_equivalent_to(CallableTypeOf[variadic_with_annotation], Callable[..., Any]))
+    signature_variadic_without_annotation: CallableTypeOf[variadic_without_annotation],
+    signature_variadic_with_annotation: CallableTypeOf[variadic_with_annotation],
+) -> None:
+    # revealed: (...) -> Unknown
+    reveal_type(signature_variadic_without_annotation)
+    # revealed: (...) -> Any
+    reveal_type(signature_variadic_with_annotation)
 ```
 
-But, a function with either `*args` or `**kwargs` (and not both) is not gradual equivalent to a
+Note that `variadic_without_annotation` and `variadic_with_annotation` are *not* considered
-callable with `...` as the parameter type.
+gradually equivalent to `Callable[..., Any]`, because the latter is not a function-like callable
+type:
+
+```py
+static_assert(not is_equivalent_to(CallableTypeOf[variadic_without_annotation], Callable[..., Any]))
+static_assert(not is_equivalent_to(CallableTypeOf[variadic_with_annotation], Callable[..., Any]))
+```
+
+A function with either `*args` or `**kwargs` (and not both) is is not equivalent to a callable with
+`...` as the parameter type.
 
 ```py
 def variadic_args(*args):
@@ -520,6 +541,15 @@ def variadic_args(*args):
 def variadic_kwargs(**kwargs):
     return
 
+def _(
+    signature_variadic_args: CallableTypeOf[variadic_args],
+    signature_variadic_kwargs: CallableTypeOf[variadic_kwargs],
+) -> None:
+    # revealed: (*args) -> Unknown
+    reveal_type(signature_variadic_args)
+    # revealed: (**kwargs) -> Unknown
+    reveal_type(signature_variadic_kwargs)
+
 static_assert(not is_equivalent_to(CallableTypeOf[variadic_args], Callable[..., Any]))
 static_assert(not is_equivalent_to(CallableTypeOf[variadic_kwargs], Callable[..., Any]))
 ```

crates/ty_python_semantic/src/types.rs

@@ -1401,7 +1401,7 @@ impl<'db> Type<'db> {
         match self {
             Type::Callable(_) => Some(self),
 
-            Type::Dynamic(_) => Some(CallableType::single(db, Signature::dynamic(self))),
+            Type::Dynamic(_) => Some(CallableType::function_like(db, Signature::dynamic(self))),
 
             Type::FunctionLiteral(function_literal) => {
                 Some(Type::Callable(function_literal.into_callable_type(db)))
@@ -9770,7 +9770,7 @@ impl<'db> BoundMethodType<'db> {
                     .iter()
                     .map(|signature| signature.bind_self(db, Some(self_instance))),
             ),
-            false,
+            true,
         )
     }
 

crates/ty_python_semantic/src/types/function.rs

@@ -943,7 +943,7 @@ impl<'db> FunctionType<'db> {
 
     /// Convert the `FunctionType` into a [`CallableType`].
     pub(crate) fn into_callable_type(self, db: &'db dyn Db) -> CallableType<'db> {
-        CallableType::new(db, self.signature(db), false)
+        CallableType::new(db, self.signature(db), true)
     }
 
     /// Convert the `FunctionType` into a [`BoundMethodType`].