[derive] Improve IntoBytes error messages #1712
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| @@ -28,7 +28,7 @@ proc-macro = true | |||
| [dependencies] | |||
| proc-macro2 = "1.0.1" | |||
| quote = "1.0.10" | |||
| syn = "2.0.46" | |||
| syn = { version = "2.0.46", features = ["full"] } | |||
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@djkoloski Do you have a sense of how we could implement using the same trick that you pulled to avoid the full feature?
I tested locally on a MacBook Pro on low battery mode, and found that the full feature increased zerocopy-derive cargo build time from 8.9s to 13.3s. That's a large percentage, but a small absolute difference. So I'm not opposed to just sticking with this impl, but it'd be cool if we could avoid it.
Codecov ReportAll modified and coverable lines are covered by tests ✅
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Hits 5191 5191
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| /// | ||
| /// ```text | ||
| /// error[E0277]: the trait bound `HasPadding<Foo, true>: ShouldBe<false>` is not satisfied | ||
| /// error[E0277]: the trait bound `(): PaddingFree<Foo, true>` is not satisfied |
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This fallback is arguably an improvement over the previous error!
| --> tests/ui-nightly/enum.rs:533:10 | ||
| | | ||
| 533 | #[derive(IntoBytes)] | ||
| | ^^^^^^^^^ the trait `ShouldBe<false>` is not implemented for `HasPadding<IntoBytes1, true>` | ||
| | ^^^^^^^^^ types with padding cannot implement `IntoBytes` |
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This is ridiculously good. I wonder if we could even say how many bytes of inter-field padding there with const generics, but that's just yak shaving.
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On Rust toolchains 1.78.0 or later, use `#[diagnostic::on_unimplemented]` to improve the error message emitted when `IntoBytes` is derived on a type with inter-field padding.
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On Rust toolchains 1.78.0 or later, use
#[diagnostic::on_unimplemented]to improve the error message emitted whenIntoBytesis derived on a type with inter-field padding.