Update datafusion-core crate to Rust 2024 edition

[timsaucer]

Which issue does this PR close?

This addresses part of #15804 but does not close it.

Rationale for this change

Now that we are on MSRV 1.88 we can use rust edition 2024, which brings let chains and other nice features. It also improves unsafe checking. In order to introduce these changes in slower way instead of one massive PR that is too difficult to manage we are updating a few crates at a time.

What changes are included in this PR?

Updates these crates to 2024.

• datafusion

Are these changes tested?

Existing unit tests. There are no functional code changes.

Are there any user-facing changes?

None.

Note

It is recommended to review with the ignore whitespace setting: https://github.com/apache/datafusion/pull/19332/files?w=1

[timsaucer]

I broke from the original plan and did just this one crate since it is such a large diff.

[alamb]

Looks good to me -- thanks @timsaucer

[alamb]

🎉

[Copilot]

Pull request overview

This PR updates the datafusion-core crate to Rust 2024 edition as part of a gradual migration strategy. The changes are purely stylistic and leverage Rust 2024 features like let chains while maintaining backward compatibility.

Key Changes:

• Edition update in Cargo.toml from 2021 to 2024
• Import reordering to follow rustfmt 2024 conventions
• Adoption of let chains to simplify nested if-let patterns
• Code formatting improvements (line breaks, alignment)

Reviewed changes

Copilot reviewed 128 out of 129 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
datafusion/core/Cargo.toml	Updates edition from workspace default to "2024"
Test files (user_defined/*.rs)	Import reordering and let chains adoption
Test files (sql/.rs, physical_optimizer/.rs)	Formatting improvements, let chains, and import sorting
Test files (parquet/.rs, fuzz_cases/.rs)	Pattern matching updates and formatting consistency
Core source files (src/*.rs)	Import reordering, let chains, and code formatting
Benchmark files (benches/*.rs)	Import statement reordering and variable renaming

All changes are non-functional and maintain existing behavior while taking advantage of Rust 2024 edition features. The migration follows best practices by updating a single crate incrementally rather than attempting a large-scale change across the entire codebase.

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