pythongh-106368: Increase Argument Clinic test coverage for IndentSta…

…ck (pythonGH-106933)

(cherry picked from commit 8d228cf)

Co-authored-by: Erlend E. Aasland <[email protected]>

Lib/test/test_clinic.py

@@ -1035,6 +1035,25 @@ def test_function_not_at_column_0(self):
                 Nested docstring here, goeth.
         """)
 
+    def test_indent_stack_no_tabs(self):
+        out = self.parse_function_should_fail("""
+            module foo
+            foo.bar
+               *vararg1: object
+            \t*vararg2: object
+        """)
+        msg = "Tab characters are illegal in the Clinic DSL."
+        self.assertIn(msg, out)
+
+    def test_indent_stack_illegal_outdent(self):
+        out = self.parse_function_should_fail("""
+            module foo
+            foo.bar
+              a: object
+             b: object
+        """)
+        self.assertIn("Illegal outdent", out)
+
     def test_directive(self):
         c = FakeClinic()
         parser = DSLParser(c)