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Detect missing derive on unresolved attribute even when not imported #142487

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@estebank estebank commented Jun 14, 2025

When encountering unresolved attributes, ensure the proc-macros for every crate in scope are added to the macro_map so that typos and missing derives are properly detected.

error: cannot find attribute `sede` in this scope
  --> $DIR/missing-derive-3.rs:20:7
   |
LL |     #[sede(untagged)]
   |       ^^^^
   |
help: the derive macros `Deserialize` and `Serialize` accept the similarly named `serde` attribute
   |
LL |     #[serde(untagged)]
   |         +

error: cannot find attribute `serde` in this scope
  --> $DIR/missing-derive-3.rs:14:7
   |
LL |     #[serde(untagged)]
   |       ^^^^^
   |
note: `serde` is imported here, but it is a crate, not an attribute
  --> $DIR/missing-derive-3.rs:4:1
   |
LL | extern crate serde;
   | ^^^^^^^^^^^^^^^^^^^
help: `serde` is an attribute that can be used by the derive macros `Deserialize` and `Serialize`, you might be missing a `derive` attribute
   |
LL + #[derive(Deserialize, Serialize)]
LL | enum B {
   |

Follow up to #134841.

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Comment on lines +172 to +179
/// Add every proc macro accessible from the current crate to the `macro_map` so diagnostics can
/// find them for suggestions.
pub(crate) fn register_macros_for_all_crates(&mut self) {
let def_ids = self.cstore().all_proc_macro_def_ids();
for def_id in def_ids {
self.get_macro_by_def_id(def_id);
}
}
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We should memoize this, but the Resolver doesn't use queries, so we should likely do that "manually" by adding a signal field to the Resolver to skip this logic after the first call.

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```
error: cannot find attribute `sede` in this scope
  --> $DIR/missing-derive-3.rs:20:7
   |
LL |     #[sede(untagged)]
   |       ^^^^
   |
help: the derive macros `Deserialize` and `Serialize` accept the similarly named `serde` attribute
   |
LL |     #[serde(untagged)]
   |         +

error: cannot find attribute `serde` in this scope
  --> $DIR/missing-derive-3.rs:14:7
   |
LL |     #[serde(untagged)]
   |       ^^^^^
   |
note: `serde` is imported here, but it is a crate, not an attribute
  --> $DIR/missing-derive-3.rs:4:1
   |
LL | extern crate serde;
   | ^^^^^^^^^^^^^^^^^^^
help: `serde` is an attribute that can be used by the derive macros `Deserialize` and `Serialize`, you might be missing a `derive` attribute
   |
LL + #[derive(Deserialize, Serialize)]
LL | enum B {
   |
```
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