Resolve TypeVar upper bounds in functools.partial (#17660)

Mostly fixes #17646

Author: hauntsaninja

mypy/checker.py

@@ -683,6 +683,8 @@ def extract_callable_type(self, inner_type: Type | None, ctx: Context) -> Callab
         inner_type = get_proper_type(inner_type)
         outer_type: CallableType | None = None
         if inner_type is not None and not isinstance(inner_type, AnyType):
+            if isinstance(inner_type, TypeVarLikeType):
+                inner_type = get_proper_type(inner_type.upper_bound)
             if isinstance(inner_type, TypeType):
                 if isinstance(inner_type.item, Instance):
                     inner_type = expand_type_by_instance(

test-data/unit/check-functools.test

@@ -541,3 +541,19 @@ p(1, "no")  # E: Argument 2 to "A" has incompatible type "str"; expected "int"
 
 q: partial[A] = partial(A, 1)  # OK
 [builtins fixtures/tuple.pyi]
+
+[case testFunctoolsPartialTypeVarBound]
+from typing import Callable, TypeVar, Type
+import functools
+
+T = TypeVar("T", bound=Callable[[str, int], str])
+S = TypeVar("S", bound=Type[int])
+
+def foo(f: T) -> T:
+    g = functools.partial(f, "foo")
+    return f
+
+def bar(f: S) -> S:
+    g = functools.partial(f, "foo")
+    return f
+[builtins fixtures/primitives.pyi]