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internal: error on duplicate #[pin] attribute #120

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internal: error on duplicate #[pin] attribute #120

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cc88d52
internal: error on duplicate `#[pin]` attribute
mentonin Mar 11, 2026
8d023c3
internal: update duplicate `#[pin]` error message
mentonin Mar 12, 2026
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8 changes: 6 additions & 2 deletions internal/src/pin_data.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -79,9 +79,13 @@ pub(crate) fn pin_data(
.map(|field| {
let len = field.attrs.len();
field.attrs.retain(|a| !a.path().is_ident("pin"));
(len != field.attrs.len(), &*field)
let diff = len - field.attrs.len();
if diff > 1 {
return Err(dcx.error(field, "#[pin] attribute specified more than once"));
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@nbdd0121 nbdd0121 Apr 14, 2026

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Instead of returning an error, could you just report the error and continue? This way it prevents cascading of error caused by not generating any code.

}
Ok((diff > 0, &*field))
})
.collect();
.collect::<Result<_, _>>()?;

for (pinned, field) in &fields {
if !pinned && is_phantom_pinned(&field.ty) {
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10 changes: 10 additions & 0 deletions tests/ui/compile-fail/pin_data/twice_pin.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,10 @@
use pin_init::*;

#[pin_data]
struct Foo {
#[pin]
#[pin]
a: usize,
}

fn main() {}
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@nbdd0121 nbdd0121 Apr 14, 2026

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If you add a user of Foo here, you should observe the "cascading error" effect

5 changes: 5 additions & 0 deletions tests/ui/compile-fail/pin_data/twice_pin.stderr
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@@ -0,0 +1,5 @@
error: #[pin] attribute specified more than once
--> tests/ui/compile-fail/pin_data/twice_pin.rs:7:5
|
7 | a: usize,
| ^^^^^^^^
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