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rustc shouldn't say 'not in scope' when using a derive macro as a macro_rules macro #76429
Description
Consider the following code (playground):
fn f() {
Debug!()
}
#[derive(Debug)]
struct S;error: cannot find macro `Debug` in this scope
--> src/lib.rs:2:5
|
2 | Debug!()
| ^^^^^
This is not particularly helpful (in fact it's incorrect). Debug is in scope, it's just not a macro rules macro. Instead the error should say something like
error: `Debug` is a derive macro, not a macro_rules! macro
--> src/lib.rs:2:5
|
2 | Debug!()
| ^^^^^ note: attempting to use a derive as a macro_rules! macroReacted by trevyn, Mikail Bagishov, Kyle, Aaron Hill, Sean Pianka, Luke, runiq and johannes
Reacted by scottmcm
Activity
jyn514 commentedon Sep 7, 2020
This would have caught the second 'library error' in https://jyn514.github.io/2020/09/05/Rust-in-2021.html.
petrochenkov commentedon Sep 7, 2020
The desirable error was reported previously, but it changed with introduction of two sub-namespaces in macro namespace - #54069.
So, derive
Debugis never found during regular name lookup now for names in fn-like macro positions (Debug!).So it needs a second lookup for diagnostics, which is currently done for other namespaces, but not other sub-namespaces in the macro namespace.
Compare with:
dario23 commentedon May 17, 2023
Current playground correctly says
so let's close this? @jyn514
jyn514 commentedon May 17, 2023
oh amazing, good find!