## Summary
This PR renames...
- `Parameter#arg` to `Parameter#name`
- `ParameterWithDefault#def` to `ParameterWithDefault#parameter` (such
that `ParameterWithDefault` has a `default` and a `parameter`)
## Test Plan
`cargo test`
## Summary
This PR renames a few AST nodes for clarity:
- `Arguments` is now `Parameters`
- `Arg` is now `Parameter`
- `ArgWithDefault` is now `ParameterWithDefault`
For now, the attribute names that reference `Parameters` directly are
changed (e.g., on `StmtFunctionDef`), but the attributes on `Parameters`
itself are not (e.g., `vararg`). We may revisit that decision in the
future.
For context, the AST node formerly known as `Arguments` is used in
function definitions. Formally (outside of the Python context),
"arguments" typically refers to "the values passed to a function", while
"parameters" typically refers to "the variables used in a function
definition". E.g., if you Google "arguments vs parameters", you'll get
some explanation like:
> A parameter is a variable in a function definition. It is a
placeholder and hence does not have a concrete value. An argument is a
value passed during function invocation.
We're thus deviating from Python's nomenclature in favor of a scheme
that we find to be more precise.
## Summary
This PR adds a new precedence level for the comprehension element. This fixes
the generator to not add parentheses around the comprehension element every
time.
The new precedence level is `COMPREHENSION_ELEMENT` and it should occur after
the `NAMED_EXPR` precedence level because named expressions are always parenthesized.
This matches the behavior of Python `ast.unparse` and tested with the
following snippet:
```python
import ast
code = ""
ast.unparse(ast.parse(code))
```
## Test Plan
Add a bunch of test cases for all the valid nodes at that position.
fixes: #5777
