Migrate proc-macro-error2 to proc-macro-error3 to avoid E0365 future-incompatibility warning

[CollinsCMK]

Future Compatibility Warning in sea-orm v2.0.0-rc.43

Description

Using sea-orm v2.0.0-rc.43 triggers a Rust future-incompatibility warning during compilation.

The warning originates from the proc-macro-error2 dependency, which re-exports the private proc_macro crate:

pub use proc_macro;

Current Rust versions still allow this behavior with a warning, but according to Rust issue #127909, it will become a hard compilation error in a future release.

As this is a release candidate for SeaORM 2.0, it would be beneficial to resolve this warning before the stable release.

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Steps to Reproduce

1. Create a new project using sea-orm v2.0.0-rc.43.

2. Build the project:

   cargo build
   

3. Observe the future compatibility warning.

4. Run the following command for additional details:

   cargo report future-incompatibilities --id 1
   

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Expected Behavior

The project should compile without future-incompatibility warnings, particularly those that are scheduled to become hard compiler errors in upcoming Rust releases.

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Actual Behavior

Compilation succeeds, but Cargo emits the following warning:

warning[E0365]: extern crate `proc_macro` is private and cannot be re-exported
   --> /home/cmk/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/proc-macro-error2-2.0.1/src/lib.rs:494:13
    |
494 |     pub use proc_macro;
    |             ^^^^^^^^^^
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #127909: https://github.com/rust-lang/rust/issues/127909

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Frequency

Always

The warning appears consistently on every clean build and dependency analysis.

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Workarounds

None known.

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Environment

Component | Version -- | -- SeaORM | 2.0.0-rc.43 Rust | rustc 1.97.1 Database | PostgreSQL Operating System | Linux (Ubuntu/Debian)

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Dependency Chain

proc-macro-error2 v2.0.1
└── sea-bae v0.2.1 (proc-macro)
    └── sea-orm-macros v2.0.0-rc.43 (proc-macro)
        └── sea-orm v2.0.0-rc.43

[tyt2y3]

Fixed upstream in `sea-bae` 0.2.2, which drops the `proc-macro-error2` dependency (now uses `proc-macro2`/`quote`/`syn` directly).

• `sea-orm-macros` already requires `sea-bae = "0.2"`, so 0.2.2 resolves with no manifest change
• `cargo update -p sea-bae` (or a fresh build) removes `proc-macro-error2` from the tree
• verified: `cargo tree -i proc-macro-error2` no longer matches any package

Closing as resolved.