Clarify what attribute and derive macros look like.

Author: m-ou-se

compiler/rustc_resolve/src/diagnostics.rs

@@ -973,7 +973,8 @@ impl<'a> Resolver<'a> {
             ) {
                 let desc = match binding.macro_kind() {
                     Some(MacroKind::Bang) => "a function-like macro".to_string(),
-                    Some(kind) => format!("{} {}", kind.article(), kind.descr_expected()),
+                    Some(MacroKind::Attr) => format!("an attribute: `#[{}]`", ident),
+                    Some(MacroKind::Derive) => format!("a derive macro: `#[derive({})]`", ident),
                     None => {
                         let res = binding.res();
                         format!("{} {}", res.article(), res.descr())

src/test/ui/issues/issue-11692-2.stderr

@@ -4,7 +4,7 @@ error: cannot find macro `test` in this scope
 LL |     concat!(test!());
    |             ^^^^
    |
-   = note: `test` is in scope, but it is an attribute
+   = note: `test` is in scope, but it is an attribute: `#[test]`
 
 error: aborting due to previous error
 

src/test/ui/macros/issue-88206.stderr

@@ -16,15 +16,15 @@ error: cannot find macro `test` in this scope
 LL |     test!();
    |     ^^^^
    |
-   = note: `test` is in scope, but it is an attribute
+   = note: `test` is in scope, but it is an attribute: `#[test]`
 
 error: cannot find macro `Copy` in this scope
   --> $DIR/issue-88206.rs:56:5
    |
 LL |     Copy!();
    |     ^^^^
    |
-   = note: `Copy` is in scope, but it is a derive macro
+   = note: `Copy` is in scope, but it is a derive macro: `#[derive(Copy)]`
 
 error: cannot find macro `Box` in this scope
   --> $DIR/issue-88206.rs:52:5

src/test/ui/macros/macro-path-prelude-fail-3.stderr

@@ -9,7 +9,7 @@ LL |     inline!();
 LL |     macro_rules! line {
    |     ----------------- similarly named macro `line` defined here
    |
-   = note: `inline` is in scope, but it is an attribute
+   = note: `inline` is in scope, but it is an attribute: `#[inline]`
 
 error: aborting due to previous error
 

src/test/ui/proc-macro/macro-namespace-reserved-2.stderr

@@ -94,15 +94,15 @@ error: cannot find macro `my_macro_attr` in this scope
 LL |     my_macro_attr!();
    |     ^^^^^^^^^^^^^
    |
-   = note: `my_macro_attr` is in scope, but it is an attribute
+   = note: `my_macro_attr` is in scope, but it is an attribute: `#[my_macro_attr]`
 
 error: cannot find macro `MyTrait` in this scope
   --> $DIR/macro-namespace-reserved-2.rs:33:5
    |
 LL |     MyTrait!();
    |     ^^^^^^^
    |
-   = note: `MyTrait` is in scope, but it is a derive macro
+   = note: `MyTrait` is in scope, but it is a derive macro: `#[derive(MyTrait)]`
 
 error: cannot find attribute `my_macro` in this scope
   --> $DIR/macro-namespace-reserved-2.rs:38:3