Keyword fn should test for membership in sets

CHANGELOG.md

@@ -8,6 +8,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
  * Fix issue with `(count nil)` throwing an exception (#759).
+ * Fix issue with keyword fn not testing for test membership in sets (#762).
 
 ## [v0.1.0b0]
 ### Added

src/basilisp/lang/keyword.py

@@ -1,9 +1,14 @@
 import threading
 from functools import total_ordering
-from typing import Iterable, Optional
+from typing import Iterable, Optional, Union
 
 from basilisp.lang import map as lmap
-from basilisp.lang.interfaces import IAssociative, ILispObject, IPersistentMap
+from basilisp.lang.interfaces import (
+    IAssociative,
+    ILispObject,
+    IPersistentMap,
+    IPersistentSet,
+)
 
 _LOCK = threading.Lock()
 _INTERN: IPersistentMap[int, "Keyword"] = lmap.PersistentMap.empty()
@@ -53,7 +58,9 @@ def __lt__(self, other):
             return False
         return self._ns < other._ns or self._name < other._name
 
-    def __call__(self, m: IAssociative, default=None):
+    def __call__(self, m: Union[IAssociative, IPersistentSet], default=None):
+        if isinstance(m, IPersistentSet):
+            return self if self in m else default
         try:
             return m.val_at(self, default)
         except AttributeError:

tests/basilisp/keyword_test.py

@@ -3,6 +3,7 @@
 import pytest
 
 from basilisp.lang import map as lmap
+from basilisp.lang import set as lset
 from basilisp.lang.keyword import Keyword, complete, keyword
 
 
@@ -46,6 +47,10 @@ def test_keyword_as_function():
     assert "hi" == kw(lmap.map({kw: "hi"}))
     assert None is kw(lmap.map({"hi": kw}))
 
+    assert kw == kw(lset.s(kw))
+    assert None is kw(lset.s(1))
+    assert "hi" is kw(lset.s(1), default="hi")
+
 
 @pytest.mark.parametrize(
     "o",