Why serde derive macros are not working?

1

Im building an ident generator and I want to add it serde support. But the code GitHub - IronThread/ident_gen: A simple ident generator that lets you chose the table that use. when ran with cargo build --all-features always throws me this error:

error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
   --> src\lib.rs:258:10
    |
258 | #[derive(Serialize, Deserialize)]
    |          ^^^^^^^^^
    |
    = note: see issue #27812 <https://github.com/rust-lang/rust/issues/27812> for more information
    = help: add `#![feature(rustc_private)]` to the crate attributes to enable
    = note: this error originates in the derive macro `Serialize` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
   --> src\lib.rs:258:21
    |
258 | #[derive(Serialize, Deserialize)]
    |                     ^^^^^^^^^^^
    |
    = note: see issue #27812 <https://github.com/rust-lang/rust/issues/27812> for more information
    = help: add `#![feature(rustc_private)]` to the crate attributes to enable
    = note: this error originates in the derive macro `Deserialize` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
   --> src\lib.rs:258:10
    |
258 | #[derive(Serialize, Deserialize)]
    |          ^^^^^^^^^
    |
    = note: see issue #27812 <https://github.com/rust-lang/rust/issues/27812> for more information
    = help: add `#![feature(rustc_private)]` to the crate attributes to enable
    = note: this error originates in the macro `try` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
   --> src\lib.rs:260:5
    |
260 |     table: String,
    |     ^^^^^^^^^^^^^
    |
    = note: see issue #27812 <https://github.com/rust-lang/rust/issues/27812> for more information
    = help: add `#![feature(rustc_private)]` to the crate attributes to enable

error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
   --> src\lib.rs:261:5
    |
261 |     ident: String,
    |     ^^^^^^^^^^^^^
    |
    = note: see issue #27812 <https://github.com/rust-lang/rust/issues/27812> for more information
    = help: add `#![feature(rustc_private)]` to the crate attributes to enable

error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
   --> src\lib.rs:258:21
    |
258 | #[derive(Serialize, Deserialize)]
    |                     ^^^^^^^^^^^
    |
    = note: see issue #27812 <https://github.com/rust-lang/rust/issues/27812> for more information
    = help: add `#![feature(rustc_private)]` to the crate attributes to enable
    = note: this error originates in the macro `try` (in Nightly builds, run with -Z macro-backtrace for more info)

It throws me that error no matter if I import the macros from serde_derive and rename them with as. I see this as a real problem for serde originating from rustc. But I dont know if make an issue on serde,on rust or a comment on https://github.com/rust-lang/rust/issues/27812.
I tested only on nightly the following version:

rustc --version --verbose:
rustc 1.71.0-nightly (458d4dae8 2023-04-25)
binary: rustc
commit-hash: 458d4dae845ec155b285681a5b88305641abb868
commit-date: 2023-04-25
host: i686-pc-windows-msvc
release: 1.71.0-nightly
LLVM version: 16.0.2

Please tell me if this is happening in other channels,thank you for your attention.

2

Renaming crates that are involved in procedural macro code generation generally goes quite badly.

If you change your Cargo.toml to

[dependencies]
serde = { optional = true, package = "serde", version = "1", features = [
    "derive",
] }

[features]
serde = ["dep:serde", "std"]
std = []

and update the reference to serde2 it builds fine with the feature enabled.

Note that the dep:dependency_name syntax is only available from Rust 1.60 and up. If you want your crate to be compatible with releases before that, you'll need to use a different name for the feature like

use_serde = ["serde", "std"]
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