From 1630477985097fcc9457dbd5f11b75ddb52bfe5b Mon Sep 17 00:00:00 2001
From: Maybe Waffle <waffle.lapkin@gmail.com>
Date: Wed, 6 Dec 2023 22:11:16 +0000
Subject: [PATCH] fix: Don't emit "missing items" diagnostic for negative impls

---
 crates/hir/src/lib.rs                              |  3 ++-
 .../src/handlers/trait_impl_missing_assoc_item.rs  | 14 ++++++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/crates/hir/src/lib.rs b/crates/hir/src/lib.rs
index 4a0c384e8a3..a5281ec32bb 100644
--- a/crates/hir/src/lib.rs
+++ b/crates/hir/src/lib.rs
@@ -671,7 +671,8 @@ impl Module {
                 _ => (),
             };
 
-            if let Some(trait_) = trait_ {
+            // Negative impls can't have items, don't emit missing items diagnostic for them
+            if let (false, Some(trait_)) = (impl_is_negative, trait_) {
                 let items = &db.trait_data(trait_.into()).items;
                 let required_items = items.iter().filter(|&(_, assoc)| match *assoc {
                     AssocItemId::FunctionId(it) => !db.function_data(it).has_body(),
diff --git a/crates/ide-diagnostics/src/handlers/trait_impl_missing_assoc_item.rs b/crates/ide-diagnostics/src/handlers/trait_impl_missing_assoc_item.rs
index 51923797ac9..56188cddf0b 100644
--- a/crates/ide-diagnostics/src/handlers/trait_impl_missing_assoc_item.rs
+++ b/crates/ide-diagnostics/src/handlers/trait_impl_missing_assoc_item.rs
@@ -112,4 +112,18 @@ impl Trait for () {
 "#,
         );
     }
+
+    #[test]
+    fn negative_impl() {
+        check_diagnostics(
+            r#"
+trait Trait {
+    fn item();
+}
+
+// Negative impls don't require any items (in fact, the forbid providing any)
+impl !Trait for () {}
+"#,
+        )
+    }
 }