Add test for macro-not-found-but-name-imported-here note.

Author: m-ou-se

src/test/ui/derives/issue-88206.rs

@@ -0,0 +1,18 @@
+// compile-flags: -Z deduplicate-diagnostics=yes
+
+#![warn(unused_imports)]
+//~^ NOTE lint level
+
+mod hey {
+    pub trait Serialize {}
+}
+
+use hey::Serialize;
+//~^ WARNING unused import
+//~| NOTE `Serialize` is imported here
+
+#[derive(Serialize)]
+//~^ ERROR cannot find derive macro `Serialize`
+struct A;
+
+fn main() {}

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

@@ -0,0 +1,26 @@
+error: cannot find derive macro `Serialize` in this scope
+  --> $DIR/issue-88206.rs:14:10
+   |
+LL | #[derive(Serialize)]
+   |          ^^^^^^^^^
+   |
+note: `Serialize` is imported here, but it is not a derive macro
+  --> $DIR/issue-88206.rs:10:5
+   |
+LL | use hey::Serialize;
+   |     ^^^^^^^^^^^^^^
+
+warning: unused import: `hey::Serialize`
+  --> $DIR/issue-88206.rs:10:5
+   |
+LL | use hey::Serialize;
+   |     ^^^^^^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> $DIR/issue-88206.rs:3:9
+   |
+LL | #![warn(unused_imports)]
+   |         ^^^^^^^^^^^^^^
+
+error: aborting due to previous error; 1 warning emitted
+