diff --git a/tests/debug.rs b/tests/debug.rs
index a614d9b13..0ea84f13b 100644
--- a/tests/debug.rs
+++ b/tests/debug.rs
@@ -53,7 +53,7 @@ fn input() {
     // debug includes all fields
     let actual = format!("{:?}", complex_struct.debug(&db));
     let expected = expect![[
-        r#"ComplexStruct { [salsa id]: 0, my_input: MyInput { [salsa id]: 0, field: 22 }, not_salsa: NotSalsa { field: "it's salsa time" } }"#
+        r#"ComplexStruct { [salsa id]: Id(0), my_input: MyInput { [salsa id]: Id(0), field: 22 }, not_salsa: NotSalsa { field: "it's salsa time" } }"#
     ]];
     expected.assert_eq(&actual);
 }
@@ -74,7 +74,7 @@ fn untracked_dependencies() {
 
     let s = leak_debug_string(&db, input);
     expect![[r#"
-        "MyInput { [salsa id]: 0, field: 22 }"
+        "MyInput { [salsa id]: Id(0), field: 22 }"
     "#]]
     .assert_debug_eq(&s);
 
@@ -118,7 +118,7 @@ fn custom_debug_impl() {
 
     let s = leak_derived_custom(&db, input, 23);
     expect![[r#"
-        "MyInput { [salsa id]: 0, field: 22 } / 23"
+        "MyInput { [salsa id]: Id(0), field: 22 } / 23"
     "#]]
     .assert_debug_eq(&s);
 }
diff --git a/tests/deletion-cascade.rs b/tests/deletion-cascade.rs
index eb6c83920..2e1150111 100644
--- a/tests/deletion-cascade.rs
+++ b/tests/deletion-cascade.rs
@@ -96,8 +96,8 @@ fn basic() {
     assert_eq!(final_result(&db, input), 2 * 2 + 2);
     db.assert_logs(expect![[r#"
         [
-            "final_result(MyInput { [salsa id]: 0 })",
-            "intermediate_result(MyInput { [salsa id]: 0 })",
+            "final_result(MyInput { [salsa id]: Id(0) })",
+            "intermediate_result(MyInput { [salsa id]: Id(0) })",
         ]"#]]);
 
     // Creates only 2 tracked structs in this revision, should delete 1
@@ -118,12 +118,12 @@ fn basic() {
     assert_eq!(final_result(&db, input), 2);
     db.assert_logs(expect![[r#"
         [
-            "intermediate_result(MyInput { [salsa id]: 0 })",
+            "intermediate_result(MyInput { [salsa id]: Id(0) })",
             "salsa_event(WillDiscardStaleOutput { execute_key: create_tracked_structs(0), output_key: MyTracked(2) })",
             "salsa_event(DidDiscard { key: MyTracked(2) })",
             "salsa_event(DidDiscard { key: contribution_from_struct(2) })",
             "salsa_event(DidDiscard { key: MyTracked(5) })",
             "salsa_event(DidDiscard { key: copy_field(5) })",
-            "final_result(MyInput { [salsa id]: 0 })",
+            "final_result(MyInput { [salsa id]: Id(0) })",
         ]"#]]);
 }
diff --git a/tests/deletion.rs b/tests/deletion.rs
index fb5298729..7b450129a 100644
--- a/tests/deletion.rs
+++ b/tests/deletion.rs
@@ -89,8 +89,8 @@ fn basic() {
     assert_eq!(final_result(&db, input), 2 * 2 + 2);
     db.assert_logs(expect![[r#"
         [
-            "final_result(MyInput { [salsa id]: 0 })",
-            "intermediate_result(MyInput { [salsa id]: 0 })",
+            "final_result(MyInput { [salsa id]: Id(0) })",
+            "intermediate_result(MyInput { [salsa id]: Id(0) })",
         ]"#]]);
 
     // Creates only 2 tracked structs in this revision, should delete 1
@@ -104,10 +104,10 @@ fn basic() {
     assert_eq!(final_result(&db, input), 2);
     db.assert_logs(expect![[r#"
         [
-            "intermediate_result(MyInput { [salsa id]: 0 })",
+            "intermediate_result(MyInput { [salsa id]: Id(0) })",
             "salsa_event(WillDiscardStaleOutput { execute_key: create_tracked_structs(0), output_key: MyTracked(2) })",
             "salsa_event(DidDiscard { key: MyTracked(2) })",
             "salsa_event(DidDiscard { key: contribution_from_struct(2) })",
-            "final_result(MyInput { [salsa id]: 0 })",
+            "final_result(MyInput { [salsa id]: Id(0) })",
         ]"#]]);
 }
diff --git a/tests/elided-lifetime-in-tracked-fn.rs b/tests/elided-lifetime-in-tracked-fn.rs
index 5ce24f478..6dc9f7201 100644
--- a/tests/elided-lifetime-in-tracked-fn.rs
+++ b/tests/elided-lifetime-in-tracked-fn.rs
@@ -59,8 +59,8 @@ fn execute() {
     assert_eq!(final_result(&db, input), 22);
     db.assert_logs(expect![[r#"
         [
-            "final_result(MyInput { [salsa id]: 0 })",
-            "intermediate_result(MyInput { [salsa id]: 0 })",
+            "final_result(MyInput { [salsa id]: Id(0) })",
+            "intermediate_result(MyInput { [salsa id]: Id(0) })",
         ]"#]]);
 
     // Intermediate result is the same, so final result does
@@ -69,14 +69,14 @@ fn execute() {
     assert_eq!(final_result(&db, input), 22);
     db.assert_logs(expect![[r#"
         [
-            "intermediate_result(MyInput { [salsa id]: 0 })",
+            "intermediate_result(MyInput { [salsa id]: Id(0) })",
         ]"#]]);
 
     input.set_field(&mut db).to(24);
     assert_eq!(final_result(&db, input), 24);
     db.assert_logs(expect![[r#"
         [
-            "intermediate_result(MyInput { [salsa id]: 0 })",
-            "final_result(MyInput { [salsa id]: 0 })",
+            "intermediate_result(MyInput { [salsa id]: Id(0) })",
+            "final_result(MyInput { [salsa id]: Id(0) })",
         ]"#]]);
 }
diff --git a/tests/expect_reuse_field_x_of_a_tracked_struct_changes_but_fn_depends_on_field_y.rs b/tests/expect_reuse_field_x_of_a_tracked_struct_changes_but_fn_depends_on_field_y.rs
index dab6c0fcc..97aa5cf59 100644
--- a/tests/expect_reuse_field_x_of_a_tracked_struct_changes_but_fn_depends_on_field_y.rs
+++ b/tests/expect_reuse_field_x_of_a_tracked_struct_changes_but_fn_depends_on_field_y.rs
@@ -79,13 +79,13 @@ fn execute() {
     assert_eq!(final_result_depends_on_x(&db, input), 22);
     db.assert_logs(expect![[r#"
         [
-            "final_result_depends_on_x(MyInput { [salsa id]: 0 })",
+            "final_result_depends_on_x(MyInput { [salsa id]: Id(0) })",
         ]"#]]);
 
     assert_eq!(final_result_depends_on_y(&db, input), 22);
     db.assert_logs(expect![[r#"
         [
-            "final_result_depends_on_y(MyInput { [salsa id]: 0 })",
+            "final_result_depends_on_y(MyInput { [salsa id]: Id(0) })",
         ]"#]]);
 
     input.set_field(&mut db).to(23);
@@ -95,7 +95,7 @@ fn execute() {
     assert_eq!(final_result_depends_on_x(&db, input), 24);
     db.assert_logs(expect![[r#"
         [
-            "final_result_depends_on_x(MyInput { [salsa id]: 0 })",
+            "final_result_depends_on_x(MyInput { [salsa id]: Id(0) })",
         ]"#]]);
 
     // y = 23 / 2 = 11
diff --git a/tests/expect_reuse_field_x_of_an_input_changes_but_fn_depends_on_field_y.rs b/tests/expect_reuse_field_x_of_an_input_changes_but_fn_depends_on_field_y.rs
index 76643443c..144cd55f2 100644
--- a/tests/expect_reuse_field_x_of_an_input_changes_but_fn_depends_on_field_y.rs
+++ b/tests/expect_reuse_field_x_of_an_input_changes_but_fn_depends_on_field_y.rs
@@ -58,13 +58,13 @@ fn execute() {
     assert_eq!(result_depends_on_x(&db, input), 23);
     db.assert_logs(expect![[r#"
         [
-            "result_depends_on_x(MyInput { [salsa id]: 0 })",
+            "result_depends_on_x(MyInput { [salsa id]: Id(0) })",
         ]"#]]);
 
     assert_eq!(result_depends_on_y(&db, input), 32);
     db.assert_logs(expect![[r#"
         [
-            "result_depends_on_y(MyInput { [salsa id]: 0 })",
+            "result_depends_on_y(MyInput { [salsa id]: Id(0) })",
         ]"#]]);
 
     input.set_x(&mut db).to(23);
@@ -72,7 +72,7 @@ fn execute() {
     assert_eq!(result_depends_on_x(&db, input), 24);
     db.assert_logs(expect![[r#"
         [
-            "result_depends_on_x(MyInput { [salsa id]: 0 })",
+            "result_depends_on_x(MyInput { [salsa id]: Id(0) })",
         ]"#]]);
 
     // input y is the same, so result depends on y
diff --git a/tests/hello_world.rs b/tests/hello_world.rs
index e14d4b6bb..50c880ee3 100644
--- a/tests/hello_world.rs
+++ b/tests/hello_world.rs
@@ -59,8 +59,8 @@ fn execute() {
     assert_eq!(final_result(&db, input), 22);
     db.assert_logs(expect![[r#"
         [
-            "final_result(MyInput { [salsa id]: 0 })",
-            "intermediate_result(MyInput { [salsa id]: 0 })",
+            "final_result(MyInput { [salsa id]: Id(0) })",
+            "intermediate_result(MyInput { [salsa id]: Id(0) })",
         ]"#]]);
 
     // Intermediate result is the same, so final result does
@@ -69,15 +69,15 @@ fn execute() {
     assert_eq!(final_result(&db, input), 22);
     db.assert_logs(expect![[r#"
         [
-            "intermediate_result(MyInput { [salsa id]: 0 })",
+            "intermediate_result(MyInput { [salsa id]: Id(0) })",
         ]"#]]);
 
     input.set_field(&mut db).to(24);
     assert_eq!(final_result(&db, input), 24);
     db.assert_logs(expect![[r#"
         [
-            "intermediate_result(MyInput { [salsa id]: 0 })",
-            "final_result(MyInput { [salsa id]: 0 })",
+            "intermediate_result(MyInput { [salsa id]: Id(0) })",
+            "final_result(MyInput { [salsa id]: Id(0) })",
         ]"#]]);
 }
 
@@ -90,8 +90,8 @@ fn red_herring() {
     assert_eq!(final_result(&db, input), 22);
     db.assert_logs(expect![[r#"
         [
-            "final_result(MyInput { [salsa id]: 0 })",
-            "intermediate_result(MyInput { [salsa id]: 0 })",
+            "final_result(MyInput { [salsa id]: Id(0) })",
+            "intermediate_result(MyInput { [salsa id]: Id(0) })",
         ]"#]]);
 
     // Create a distinct input and mutate it.
diff --git a/tests/input_with_ids.rs b/tests/input_with_ids.rs
index 3656c8e3b..6e6e6ac6d 100644
--- a/tests/input_with_ids.rs
+++ b/tests/input_with_ids.rs
@@ -38,7 +38,7 @@ fn test_debug() {
     let input = MyInput::new(&mut db, 50, 10, Field {});
 
     let actual = format!("{:?}", input.debug(&db));
-    let expected = expect!["MyInput { [salsa id]: 0, id_one: 50, id_two: 10, field: Field }"];
+    let expected = expect!["MyInput { [salsa id]: Id(0), id_one: 50, id_two: 10, field: Field }"];
     expected.assert_eq(&actual);
 }
 
diff --git a/tests/interned-struct-with-lifetime.rs b/tests/interned-struct-with-lifetime.rs
index 2e7bee80c..765d29101 100644
--- a/tests/interned-struct-with-lifetime.rs
+++ b/tests/interned-struct-with-lifetime.rs
@@ -52,7 +52,7 @@ fn execute() {
     let mut db = Database::default();
 
     expect![[r#"
-        "InternedPair { [salsa id]: 0, data: (InternedString { [salsa id]: 0, data: \"Hello, \" }, InternedString { [salsa id]: 1, data: \"World, \" }) }"
+        "InternedPair { [salsa id]: Id(0), data: (InternedString { [salsa id]: Id(0), data: \"Hello, \" }, InternedString { [salsa id]: Id(1), data: \"World, \" }) }"
     "#]].assert_debug_eq(&intern_stuff(&db));
     db.assert_logs(expect!["[]"]);
 }
diff --git a/tests/singleton.rs b/tests/singleton.rs
index adf339ed9..80963e953 100644
--- a/tests/singleton.rs
+++ b/tests/singleton.rs
@@ -68,6 +68,6 @@ fn debug() {
     let db = Database::default();
     let input = MyInput::new(&db, 3, 4);
     let actual = format!("{:?}", input.debug(&db));
-    let expected = expect!["MyInput { [salsa id]: 0, field: 3, id_field: 4 }"];
+    let expected = expect!["MyInput { [salsa id]: Id(0), field: 3, id_field: 4 }"];
     expected.assert_eq(&actual);
 }
diff --git a/tests/specify_tracked_fn_in_rev_1_but_not_2.rs b/tests/specify_tracked_fn_in_rev_1_but_not_2.rs
index a96e65057..562780c66 100644
--- a/tests/specify_tracked_fn_in_rev_1_but_not_2.rs
+++ b/tests/specify_tracked_fn_in_rev_1_but_not_2.rs
@@ -96,13 +96,13 @@ fn test_run_0() {
         [
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: final_result(0) } }",
-            "final_result(MyInput { [salsa id]: 0 })",
+            "final_result(MyInput { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: create_tracked(0) } }",
-            "create_tracked(MyInput { [salsa id]: 0 })",
+            "create_tracked(MyInput { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: read_maybe_specified(0) } }",
-            "read_maybe_specified(MyTracked { [salsa id]: 0 })",
+            "read_maybe_specified(MyTracked { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
         ]"#]]);
 }
@@ -117,13 +117,13 @@ fn test_run_5() {
         [
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: final_result(0) } }",
-            "final_result(MyInput { [salsa id]: 0 })",
+            "final_result(MyInput { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: create_tracked(0) } }",
-            "create_tracked(MyInput { [salsa id]: 0 })",
+            "create_tracked(MyInput { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: read_maybe_specified(0) } }",
-            "read_maybe_specified(MyTracked { [salsa id]: 0 })",
+            "read_maybe_specified(MyTracked { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
         ]"#]]);
 }
@@ -138,16 +138,16 @@ fn test_run_10() {
         [
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: final_result(0) } }",
-            "final_result(MyInput { [salsa id]: 0 })",
+            "final_result(MyInput { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: create_tracked(0) } }",
-            "create_tracked(MyInput { [salsa id]: 0 })",
+            "create_tracked(MyInput { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: read_maybe_specified(0) } }",
-            "read_maybe_specified(MyTracked { [salsa id]: 0 })",
+            "read_maybe_specified(MyTracked { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: maybe_specified(0) } }",
-            "maybe_specified(MyTracked { [salsa id]: 0 })",
+            "maybe_specified(MyTracked { [salsa id]: Id(0) })",
         ]"#]]);
 }
 
@@ -161,16 +161,16 @@ fn test_run_20() {
         [
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: final_result(0) } }",
-            "final_result(MyInput { [salsa id]: 0 })",
+            "final_result(MyInput { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: create_tracked(0) } }",
-            "create_tracked(MyInput { [salsa id]: 0 })",
+            "create_tracked(MyInput { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: read_maybe_specified(0) } }",
-            "read_maybe_specified(MyTracked { [salsa id]: 0 })",
+            "read_maybe_specified(MyTracked { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: maybe_specified(0) } }",
-            "maybe_specified(MyTracked { [salsa id]: 0 })",
+            "maybe_specified(MyTracked { [salsa id]: Id(0) })",
         ]"#]]);
 }
 
@@ -188,13 +188,13 @@ fn test_run_0_then_5_then_20() {
         [
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: final_result(0) } }",
-            "final_result(MyInput { [salsa id]: 0 })",
+            "final_result(MyInput { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: create_tracked(0) } }",
-            "create_tracked(MyInput { [salsa id]: 0 })",
+            "create_tracked(MyInput { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: read_maybe_specified(0) } }",
-            "read_maybe_specified(MyTracked { [salsa id]: 0 })",
+            "read_maybe_specified(MyTracked { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
         ]"#]]);
 
@@ -209,7 +209,7 @@ fn test_run_0_then_5_then_20() {
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: create_tracked(0) } }",
-            "create_tracked(MyInput { [salsa id]: 0 })",
+            "create_tracked(MyInput { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: DidValidateMemoizedValue { database_key: read_maybe_specified(0) } }",
@@ -228,17 +228,17 @@ fn test_run_0_then_5_then_20() {
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: create_tracked(0) } }",
-            "create_tracked(MyInput { [salsa id]: 0 })",
+            "create_tracked(MyInput { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillDiscardStaleOutput { execute_key: create_tracked(0), output_key: maybe_specified(0) } }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: maybe_specified(0) } }",
-            "maybe_specified(MyTracked { [salsa id]: 0 })",
+            "maybe_specified(MyTracked { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: read_maybe_specified(0) } }",
-            "read_maybe_specified(MyTracked { [salsa id]: 0 })",
+            "read_maybe_specified(MyTracked { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: final_result(0) } }",
-            "final_result(MyInput { [salsa id]: 0 })",
+            "final_result(MyInput { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
         ]"#]]);
@@ -258,13 +258,13 @@ fn test_run_0_then_5_then_10_then_20() {
         [
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: final_result(0) } }",
-            "final_result(MyInput { [salsa id]: 0 })",
+            "final_result(MyInput { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: create_tracked(0) } }",
-            "create_tracked(MyInput { [salsa id]: 0 })",
+            "create_tracked(MyInput { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: read_maybe_specified(0) } }",
-            "read_maybe_specified(MyTracked { [salsa id]: 0 })",
+            "read_maybe_specified(MyTracked { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
         ]"#]]);
 
@@ -279,7 +279,7 @@ fn test_run_0_then_5_then_10_then_20() {
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: create_tracked(0) } }",
-            "create_tracked(MyInput { [salsa id]: 0 })",
+            "create_tracked(MyInput { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: DidValidateMemoizedValue { database_key: read_maybe_specified(0) } }",
@@ -298,12 +298,12 @@ fn test_run_0_then_5_then_10_then_20() {
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: create_tracked(0) } }",
-            "create_tracked(MyInput { [salsa id]: 0 })",
+            "create_tracked(MyInput { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillDiscardStaleOutput { execute_key: create_tracked(0), output_key: maybe_specified(0) } }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: maybe_specified(0) } }",
-            "maybe_specified(MyTracked { [salsa id]: 0 })",
+            "maybe_specified(MyTracked { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: DidValidateMemoizedValue { database_key: read_maybe_specified(0) } }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: DidValidateMemoizedValue { database_key: final_result(0) } }",
         ]"#]]);
@@ -318,16 +318,16 @@ fn test_run_0_then_5_then_10_then_20() {
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: create_tracked(0) } }",
-            "create_tracked(MyInput { [salsa id]: 0 })",
+            "create_tracked(MyInput { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: maybe_specified(0) } }",
-            "maybe_specified(MyTracked { [salsa id]: 0 })",
+            "maybe_specified(MyTracked { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: read_maybe_specified(0) } }",
-            "read_maybe_specified(MyTracked { [salsa id]: 0 })",
+            "read_maybe_specified(MyTracked { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: final_result(0) } }",
-            "final_result(MyInput { [salsa id]: 0 })",
+            "final_result(MyInput { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
         ]"#]]);
@@ -343,13 +343,13 @@ fn test_run_5_then_20() {
         [
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: final_result(0) } }",
-            "final_result(MyInput { [salsa id]: 0 })",
+            "final_result(MyInput { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: create_tracked(0) } }",
-            "create_tracked(MyInput { [salsa id]: 0 })",
+            "create_tracked(MyInput { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: read_maybe_specified(0) } }",
-            "read_maybe_specified(MyTracked { [salsa id]: 0 })",
+            "read_maybe_specified(MyTracked { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
         ]"#]]);
 
@@ -360,17 +360,17 @@ fn test_run_5_then_20() {
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: create_tracked(0) } }",
-            "create_tracked(MyInput { [salsa id]: 0 })",
+            "create_tracked(MyInput { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillDiscardStaleOutput { execute_key: create_tracked(0), output_key: maybe_specified(0) } }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: maybe_specified(0) } }",
-            "maybe_specified(MyTracked { [salsa id]: 0 })",
+            "maybe_specified(MyTracked { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: read_maybe_specified(0) } }",
-            "read_maybe_specified(MyTracked { [salsa id]: 0 })",
+            "read_maybe_specified(MyTracked { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillExecute { database_key: final_result(0) } }",
-            "final_result(MyInput { [salsa id]: 0 })",
+            "final_result(MyInput { [salsa id]: Id(0) })",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
             "Event { runtime_id: RuntimeId { counter: 0 }, kind: WillCheckCancellation }",
         ]"#]]);
diff --git a/tests/tracked_fn_read_own_entity.rs b/tests/tracked_fn_read_own_entity.rs
index 0aa354dcc..b00750c2f 100644
--- a/tests/tracked_fn_read_own_entity.rs
+++ b/tests/tracked_fn_read_own_entity.rs
@@ -60,8 +60,8 @@ fn one_entity() {
     assert_eq!(final_result(&db, input), 22);
     db.assert_logs(expect![[r#"
         [
-            "final_result(MyInput { [salsa id]: 0 })",
-            "intermediate_result(MyInput { [salsa id]: 0 })",
+            "final_result(MyInput { [salsa id]: Id(0) })",
+            "intermediate_result(MyInput { [salsa id]: Id(0) })",
         ]"#]]);
 
     // Intermediate result is the same, so final result does
@@ -70,15 +70,15 @@ fn one_entity() {
     assert_eq!(final_result(&db, input), 22);
     db.assert_logs(expect![[r#"
         [
-            "intermediate_result(MyInput { [salsa id]: 0 })",
+            "intermediate_result(MyInput { [salsa id]: Id(0) })",
         ]"#]]);
 
     input.set_field(&mut db).to(24);
     assert_eq!(final_result(&db, input), 24);
     db.assert_logs(expect![[r#"
         [
-            "intermediate_result(MyInput { [salsa id]: 0 })",
-            "final_result(MyInput { [salsa id]: 0 })",
+            "intermediate_result(MyInput { [salsa id]: Id(0) })",
+            "final_result(MyInput { [salsa id]: Id(0) })",
         ]"#]]);
 }
 
@@ -91,8 +91,8 @@ fn red_herring() {
     assert_eq!(final_result(&db, input), 22);
     db.assert_logs(expect![[r#"
         [
-            "final_result(MyInput { [salsa id]: 0 })",
-            "intermediate_result(MyInput { [salsa id]: 0 })",
+            "final_result(MyInput { [salsa id]: Id(0) })",
+            "intermediate_result(MyInput { [salsa id]: Id(0) })",
         ]"#]]);
 
     // Create a distinct input and mutate it.
diff --git a/tests/tracked_fn_read_own_specify.rs b/tests/tracked_fn_read_own_specify.rs
index 5785464af..5049a1401 100644
--- a/tests/tracked_fn_read_own_specify.rs
+++ b/tests/tracked_fn_read_own_specify.rs
@@ -56,7 +56,7 @@ fn execute() {
     assert_eq!(tracked_fn(&db, input), 2222);
     db.assert_logs(expect![[r#"
         [
-            "tracked_fn(MyInput { [salsa id]: 0, field: 22 })",
+            "tracked_fn(MyInput { [salsa id]: Id(0), field: 22 })",
         ]"#]]);
 
     // A "synthetic write" causes the system to act *as though* some
diff --git a/tests/tracked_with_struct_db.rs b/tests/tracked_with_struct_db.rs
index 737aef256..6a3889653 100644
--- a/tests/tracked_with_struct_db.rs
+++ b/tests/tracked_with_struct_db.rs
@@ -51,16 +51,24 @@ fn execute() {
     let t1 = create_tracked_list(&db, input);
     expect_test::expect![[r#"
         MyTracked {
-            [salsa id]: 1,
+            [salsa id]: Id(
+                1,
+            ),
             data: MyInput {
-                [salsa id]: 0,
+                [salsa id]: Id(
+                    0,
+                ),
                 field: "foo",
             },
             next: Next(
                 MyTracked {
-                    [salsa id]: 0,
+                    [salsa id]: Id(
+                        0,
+                    ),
                     data: MyInput {
-                        [salsa id]: 0,
+                        [salsa id]: Id(
+                            0,
+                        ),
                         field: "foo",
                     },
                     next: None,