1 files changed, 18 insertions, 8 deletions
diff --git a/testing/diff.ts b/testing/diff.ts
index e951032f5..4c96b3b28 100644
--- a/testing/diff.ts
+++ b/testing/diff.ts
@@ -54,12 +54,18 @@ export default function diff<T>(A: T[], B: T[]): Array<DiffResult<T>> {
   if (!M && !N && !suffixCommon.length && !prefixCommon.length) return [];
   if (!N) {
     return [
-      ...prefixCommon.map(c => ({ type: DiffType.common, value: c })),
-      ...A.map(a => ({
-        type: swapped ? DiffType.added : DiffType.removed,
-        value: a
-      })),
-      ...suffixCommon.map(c => ({ type: DiffType.common, value: c }))
+      ...prefixCommon.map(
+        (c): DiffResult<typeof c> => ({ type: DiffType.common, value: c })
+      ),
+      ...A.map(
+        (a): DiffResult<typeof a> => ({
+          type: swapped ? DiffType.added : DiffType.removed,
+          value: a
+        })
+      ),
+      ...suffixCommon.map(
+        (c): DiffResult<typeof c> => ({ type: DiffType.common, value: c })
+      )
     ];
   }
   const offset = N;
@@ -198,8 +204,12 @@ export default function diff<T>(A: T[], B: T[]): Array<DiffResult<T>> {
     );
   }
   return [
-    ...prefixCommon.map(c => ({ type: DiffType.common, value: c })),
+    ...prefixCommon.map(
+      (c): DiffResult<typeof c> => ({ type: DiffType.common, value: c })
+    ),
     ...backTrace(A, B, fp[delta + offset], swapped),
-    ...suffixCommon.map(c => ({ type: DiffType.common, value: c }))
+    ...suffixCommon.map(
+      (c): DiffResult<typeof c> => ({ type: DiffType.common, value: c })
+    )
   ];
 }