fix: reject a number on the left-hand side of + as well

[yu2971512385-ui]

wait_base.__radd__ deliberately turns a non-zero number into a TypeError at the +, with the reasoning spelled out in the comment there:

Any other number is not a wait strategy, and saying so here raises TypeError at the + rather than building a combination that fails when called.

__add__ has no such check, so the mirror expression does exactly what that comment is about:

>>> w = tenacity.wait_fixed(1) + 5
>>> w  # a wait_combine holding an int
>>> Retrying(wait=w, stop=tenacity.stop_after_attempt(3))(flaky)
TypeError: 'int' object is not callable

The error arrives on the first retry, inside wait_combine.__call__, pointing at tenacity rather than at the line that built the strategy. 5 + tenacity.wait_fixed(1) — the same mistake written the other way round — already fails immediately and is covered by test_wait_radd_rejects_non_zero_number.

Change

__add__ returns NotImplemented when the operand is not callable, so Python falls through to the operand's __radd__ and raises the usual unsupported operand type(s) for +: 'wait_fixed' and 'int'. The annotation moves from wait_base to WaitBaseT, matching what wait_combine and __radd__ already accept, so wait_fixed(1) + (lambda retry_state: 2.0) keeps working.

Behaviour after the change:

expression	before	after
w + 5	wait_combine that raises when called	TypeError at the +
5 + w	TypeError at the +	unchanged
0 + w / sum([w1, w2])	identity / wait_combine	unchanged
w1 + w2, w + callable	wait_combine	unchanged

Tests

• test_wait_add_rejects_number — the mirror of the existing __radd__ test; it fails without the change.
• test_wait_add_plain_callable — the callable case keeps building a wait_combine.

pytest tests/ is 185 passed, 1 skipped; mypy tenacity/wait.py is clean (the 3 errors mypy tenacity/ reports in asyncio/__init__.py are there on a clean checkout too).

Disclosure: found and prepared with AI assistance — the asymmetry came out of a sweep over the wait strategy operators; I verified the behaviour and ran the suite and mypy locally.