LazyContext.infer() should return a set.

test/completion/generators.py

@@ -108,7 +108,7 @@ for c in Counter(3, 8):
 
 
 # -----------------
-# tuples
+# tuple assignments
 # -----------------
 def gen():
     if random.choice([0,1]):
@@ -148,6 +148,9 @@ a
 #? str()
 b
 
+a, = (a for a in [1])
+#? int()
+a
 
 # -----------------
 # More complicated access