mbrobbel commented on code in PR #8227:
URL: https://github.com/apache/arrow-rs/pull/8227#discussion_r2328608065
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arrow-cast/src/pretty.rs:
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@@ -60,7 +60,7 @@ use crate::display::{ArrayFormatter, FormatOptions};
/// | 5 | e |
/// +---+---+"#);
/// ```
-pub fn pretty_format_batches(results: &[RecordBatch]) -> Result<impl Display,
ArrowError> {
+pub fn pretty_format_batches(results: &[RecordBatch]) -> Result<impl Display +
use<>, ArrowError> {
Review Comment:
The relevant change is documented here
https://doc.rust-lang.org/edition-guide/rust-2024/rpit-lifetime-capture.html
> In Rust 2021 and earlier editions, when the use<..> bound is not present,
generic lifetime parameters are only captured when they appear syntactically
within a bound in RPIT opaque types in the signature of bare functions and
associated functions and methods within inherent impls. However, starting in
Rust 2024, these in-scope generic lifetime parameters are unconditionally
captured.
The returned type does not capture the lifetime of the recordbatch slice, so
`use<>` indicates this.
For users this means that the following still compiles in 2024 Rust:
```rust
let record_batches: &[RecordBatch] = ...;
let pretty = pretty_format_batches(record_batches)?;
drop(record_batches);
dbg!(pretty);
```
Without `use<>` in 2024 Rust `rustc` would complain about `record_batches`
still being borrowed when dropped.
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