Add tests for positional only params

test/completion/positional_only_params.py

@@ -0,0 +1,29 @@
+# python >= 3.8
+
+def positional_only_call(a, /, b):
+    #? str()
+    a
+    #? int()
+    b
+    return a + b
+
+
+#? int() str()
+positional_only_call('', 1)
+
+
+def positional_only_call2(a, /, b=3):
+    return a + b
+
+#? int()
+positional_only_call2(1)
+#? int()
+positional_only_call2(SOMETHING_UNDEFINED)
+#? str()
+positional_only_call2(SOMETHING_UNDEFINED, '')
+
+# Maybe change this? Because it's actually not correct
+#? int() str()
+positional_only_call2(a=1, b='')
+#? tuple str()
+positional_only_call2(b='', a=tuple)