Detect when attribute is provided by missing `derive` macro

2025-06-12T21:28:49+00:00

``` error: cannot find attribute `empty_helper` in this scope --> $DIR/derive-helper-legacy-limits.rs:17:3 | LL | #[empty_helper] | ^^^^^^^^^^^^ | help: `empty_helper` is an attribute that can be used by the derive macro `Empty`, you might be missing a `derive` attribute | LL + #[derive(Empty)] LL | struct S2; | ``` Look at proc-macro attributes when encountering unknown attribute ``` error: cannot find attribute `sede` in this scope --> src/main.rs:18:7 | 18 | #[sede(untagged)] | ^^^^ | help: the derive macros `Serialize` and `Deserialize` accept the similarly named `serde` attribute | 18 | #[serde(untagged)] | ~~~~~ error: cannot find attribute `serde` in this scope --> src/main.rs:12:7 | 12 | #[serde(untagged)] | ^^^^^ | = note: `serde` is in scope, but it is a crate, not an attribute help: `serde` is an attribute that can be used by the derive macros `Serialize` and `Deserialize`, you might be missing a `derive` attribute | 10 | #[derive(Serialize, Deserialize)] | ```

Show number in error message even for one error

2023-11-24T18:15:52+00:00

Co-authored-by: Adrian

Move /src/test to /tests

2023-01-11T09:32:08+00:00

rust/tests/ui/proc-macro/derive-helper-legacy-limits.stderr, branch try-perf

Detect when attribute is provided by missing `derive` macro

Show number in error message even for one error

Move /src/test to /tests