[red-knot] Callable types are disjoint from literals

crates/red_knot_python_semantic/resources/mdtest/type_properties/is_disjoint_from.md

@@ -379,3 +379,15 @@ static_assert(not is_disjoint_from(Callable[..., None], Callable[[Literal[1]], N
 static_assert(not is_disjoint_from(Callable[[], Never], Callable[[], Never]))
 static_assert(not is_disjoint_from(Callable[[Never], str], Callable[[Never], int]))
 ```
+
+A callable type is disjoint from all literal types.
+
+```py
+from knot_extensions import CallableTypeOf, is_disjoint_from, static_assert
+from typing_extensions import Callable, Literal, Never
+
+static_assert(is_disjoint_from(Callable[[], None], Literal[""]))
+static_assert(is_disjoint_from(Callable[[], None], Literal[b""]))
+static_assert(is_disjoint_from(Callable[[], None], Literal[1]))
+static_assert(is_disjoint_from(Callable[[], None], Literal[True]))
+```

crates/red_knot_python_semantic/src/types.rs

@@ -1393,6 +1393,20 @@ impl<'db> Type<'db> {
                 false
             }
 
+            (
+                Type::Callable(_),
+                Type::StringLiteral(_) | Type::BytesLiteral(_) | Type::SliceLiteral(_),
+            )
+            | (
+                Type::StringLiteral(_) | Type::BytesLiteral(_) | Type::SliceLiteral(_),
+                Type::Callable(_),
+            ) => {
+                // A callable type is disjoint from other literal types. For example,
+                // `Type::StringLiteral` must be an instance of exactly `str`, not a subclass
+                // of `str`, and `str` is not callable. The same applies to other literal types.
+                true
+            }
+
             (Type::Callable(_), _) | (_, Type::Callable(_)) => {
                 // TODO: Implement disjointness for general callable type with other types
                 false