Fix correction and add tests for LiteralString

Author: MatthewMckee4

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

@@ -107,6 +107,9 @@ static_assert(is_assignable_to(Literal["foo"], Sequence[str]))
 static_assert(is_assignable_to(Literal["foo"], Sequence[Any]))
 
 static_assert(is_assignable_to(LiteralString, str))
+static_assert(is_assignable_to(LiteralString, Sequence))
+static_assert(is_assignable_to(LiteralString, Sequence[str]))
+static_assert(is_assignable_to(LiteralString, Sequence[Any]))
 
 static_assert(not is_assignable_to(Literal["foo"], Literal["bar"]))
 static_assert(not is_assignable_to(str, Literal["foo"]))

crates/ty_python_semantic/src/types.rs

@@ -1655,8 +1655,9 @@ impl<'db> Type<'db> {
                 }
             }
 
-            _ if self.literal_fallback_instance(db))
-                .is_some_and(|instance| instance.is_assignable_to(db, target) =>
+            _ if self
+                .literal_fallback_instance(db)
+                .is_some_and(|instance| instance.is_assignable_to(db, target)) =>
             {
                 true
             }