From 2a6404f4c0b6a66e254026b1643598d12a644f55 Mon Sep 17 00:00:00 2001
From: Ary Borenszweig <asterite@gmail.com>
Date: Wed, 9 Oct 2024 10:41:10 -0300
Subject: [PATCH] fix: don't warn on unuse global if it has an abi annotation

---
 .../src/hir/def_collector/dc_mod.rs             | 17 ++++++++++-------
 .../noirc_frontend/src/tests/unused_items.rs    | 13 +++++++++++++
 2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/compiler/noirc_frontend/src/hir/def_collector/dc_mod.rs b/compiler/noirc_frontend/src/hir/def_collector/dc_mod.rs
index 65912023661..b9ce8f361f7 100644
--- a/compiler/noirc_frontend/src/hir/def_collector/dc_mod.rs
+++ b/compiler/noirc_frontend/src/hir/def_collector/dc_mod.rs
@@ -1203,6 +1203,7 @@ pub(crate) fn collect_global(
     let global = global.item;
 
     let name = global.pattern.name_ident().clone();
+    let is_abi = global.attributes.iter().any(|attribute| attribute.is_abi());
 
     let global_id = interner.push_empty_global(
         name.clone(),
@@ -1217,13 +1218,15 @@ pub(crate) fn collect_global(
     // Add the statement to the scope so its path can be looked up later
     let result = def_map.modules[module_id.0].declare_global(name.clone(), visibility, global_id);
 
-    let parent_module_id = ModuleId { krate: crate_id, local_id: module_id };
-    interner.usage_tracker.add_unused_item(
-        parent_module_id,
-        name,
-        UnusedItem::Global(global_id),
-        visibility,
-    );
+    if !is_abi {
+        let parent_module_id = ModuleId { krate: crate_id, local_id: module_id };
+        interner.usage_tracker.add_unused_item(
+            parent_module_id,
+            name,
+            UnusedItem::Global(global_id),
+            visibility,
+        );
+    }
 
     let error = result.err().map(|(first_def, second_def)| {
         let err =
diff --git a/compiler/noirc_frontend/src/tests/unused_items.rs b/compiler/noirc_frontend/src/tests/unused_items.rs
index c89670a9043..51bdf785688 100644
--- a/compiler/noirc_frontend/src/tests/unused_items.rs
+++ b/compiler/noirc_frontend/src/tests/unused_items.rs
@@ -211,6 +211,19 @@ fn warns_on_unused_global() {
     assert_eq!(item.item_type(), "global");
 }
 
+#[test]
+fn does_not_warn_on_unused_global_if_it_has_an_abi_attribute() {
+    let src = r#"
+    contract foo {
+        #[abi(notes)]
+        global bar = 1;
+    }
+
+    fn main() {}
+    "#;
+    assert_no_errors(src);
+}
+
 #[test]
 fn no_warning_on_inner_struct_when_parent_is_used() {
     let src = r#"