Re: [PATCH v3 05/15] rust: pin-init: rewrite `derive(Zeroable)` and `derive(MaybeZeroable)` using `syn`

[Gary Guo]

On Wed Jan 14, 2026 at 6:18 PM GMT, Benno Lossin wrote:
> Rewrite the two derive macros for `Zeroable` using `syn`. One positive
> side effect of this change is that tuple structs are now supported by
> them. Additionally, syntax errors and the error emitted when trying to
> use one of the derive macros on an `enum` are improved. Otherwise no
> functional changes intended.
> 
> For example:
> 
>     #[derive(Zeroable)]
>     enum Num {
>         A(u32),
>         B(i32),
>     }
> 
> Produced this error before this commit:
> 
>     error: no rules expected keyword `enum`
>      --> tests/ui/compile-fail/zeroable/enum.rs:5:1
>       |
>     5 | enum Num {
>       | ^^^^ no rules expected this token in macro call
>       |
>     note: while trying to match keyword `struct`
>      --> src/macros.rs
>       |
>       |             $vis:vis struct $name:ident
>       |                      ^^^^^^
> 
> Now the error is:
> 
>     error: cannot derive `Zeroable` for an enum
>      --> tests/ui/compile-fail/zeroable/enum.rs:5:1
>       |
>     5 | enum Num {
>       | ^^^^
> 
>     error: cannot derive `Zeroable` for an enum
> 
> Tested-by: Andreas Hindborg <a.hindborg@xxxxxxxxxx>
> Signed-off-by: Benno Lossin <lossin@xxxxxxxxxx>

Reviewed-by: Gary Guo <gary@xxxxxxxxxxx>

> ---
> Changes in v3:
> * use DiagCtxt error handling
> Changes in v2:
> * improved error handling
> ---
>  rust/pin-init/internal/src/diagnostics.rs |   2 -
>  rust/pin-init/internal/src/lib.rs         |   9 +-
>  rust/pin-init/internal/src/zeroable.rs    | 155 ++++++++++------------
>  rust/pin-init/src/macros.rs               | 124 -----------------
>  4 files changed, 74 insertions(+), 216 deletions(-)