TransientVector supports being called and nth

CHANGELOG.md

@@ -12,6 +12,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Changed
  * Add `test` and `tests` directories to `PYTHONPATH` automatically during `basilisp test` CLI invocations (#1069)
 
+### Fixed
+ * Fix a bug where transient vectors were not callable and did not support `nth` (#1331)
+
 ## [v0.5.0]
 ### Added
  * Added support for Python 3.14 (#1282)

src/basilisp/lang/runtime.py

@@ -35,6 +35,7 @@
     IAssociative,
     IBlockingDeref,
     IDeref,
+    IIndexed,
     ILookup,
     IMapEntry,
     IPersistentCollection,
@@ -1454,6 +1455,7 @@ def _nth_none(_: None, i: int, notfound=__nth_sentinel) -> None:
 
 
 @nth.register(Sequence)
+@nth.register(IIndexed)
 def _nth_sequence(coll: Sequence, i: int, notfound=__nth_sentinel):
     try:
         return coll[i]

src/basilisp/lang/vector.py

@@ -51,6 +51,12 @@ def __eq__(self, other):
     def __len__(self):
         return len(self._inner)
 
+    def __getitem__(self, item):
+        return self._inner[item]
+
+    def __call__(self, k: int) -> T | None:
+        return self._inner[k]
+
     def cons_transient(self, *elems: T) -> "TransientVector[T]":  # type: ignore[override]
         for elem in elems:
             self._inner.append(elem)

tests/basilisp/core/test_transients.lpy

@@ -94,6 +94,16 @@
       []
       [:a :b :c]))
 
+  (testing "callable"
+    (are [v idx res] (= res ((transient v) idx))
+      [1]        0 1
+      [:a :b :c] 1 :b)
+
+    (are [v idx] (thrown? python/IndexError ((transient v) idx))
+      []         0
+      []         1
+      [:a :b :c] 4))
+
   (testing "count"
     (let [trx (volatile! (transient [:a :b :c]))]
       (is (= 3 (count @trx)))
@@ -116,13 +126,20 @@
 
   (testing "get"
     (are [x y z] (= z (get (transient x) y))
-      []         1  nil
+      []         1 nil
       [:a :b :c] 1 :b)
 
     (is (= :e (get (transient [:a :b :c]) 4 :e))))
 
-  (testing "not seqable"
-    (is (thrown? python/TypeError (seq (transient []))))))
+  (testing "nth"
+    (are [v idx res] (= res (nth (transient v) idx))
+      [1]        0 1
+      [:a :b :c] 1 :b)
+
+    (are [v idx] (thrown? python/IndexError (nth (transient v) idx))
+      []         0
+      []         1
+      [:a :b :c] 4)))
 
 (deftest assoc!-test
   (testing "maps"