Fixes#15012.
```python
def f():
# panics when the code can't find the loop variable
values = [1, 2, 3]
result = []
for i in values:
result.append(i + 1)
del i
```
I'm not sure exactly why this test case panics, but I suspect the `del
i` removes the binding from the semantic model's symbols.
I changed the code to search for the correct binding by directly
iterating through the bindings. Since we know exactly which binding we
want, this should find the loop variable without any complications.
Fixes#14969.
The issue was that this line:
```rust
let from_assign_to_loop = TextRange::new(binding_stmt.end(), for_stmt.start());
```
was not safe if the binding was after the target. The only way (at least
that I can think of) this can happen is if they are in different scopes,
so it now checks for that before checking if there are usages between
the two.
## Summary
This PR ensures that if a list `x` is modified within a `for` loop, we
avoid flagging `list(x)` as unnecessary. Previously, we only detected
calls to exactly `.append`, and they couldn't be nested within other
statements.
Closes https://github.com/astral-sh/ruff/issues/9925.
## Summary
Adds `find_assigned_value` a function which gets the `&Expr` assigned to
a given `id` if one exists in the semantic model.
Open TODOs:
- [ ] Handle `binding.kind.is_unpacked_assignment()`: I am bit confused
by this one. The snippet from its documentation does not appear to be
counted as an unpacked assignment and the only ones I could find for
which that was true were invalid Python like:
```python
x, y = 1
```
- [ ] How to handle AugAssign. Can we combine statements like:
```python
(a, b) = [(1, 2, 3), (4,)]
a += (6, 7)
```
to get the full value for a? Code currently just returns `None` for
these assign types
- [ ] Multi target assigns
```python
m_c = (m_d, m_e) = (0, 0)
trio.sleep(m_c) # OK
trio.sleep(m_d) # TRIO115
trio.sleep(m_e) # TRIO115
```
## Test Plan
Used the function in two rules:
- `TRIO115`
- `PERF101`
Expanded both their fixtures for explicit multi target check
Dylan
w0nder1ng
Charlie Marsh
Alex Waygood
qdegraaf
Dhruv Manilawala