2 files changed, 36 insertions, 1 deletions
diff --git a/tests/ui/unit_cmp.rs b/tests/ui/unit_cmp.rs
index 93f5b87c3d2..0a0fe3a1990 100644
--- a/tests/ui/unit_cmp.rs
+++ b/tests/ui/unit_cmp.rs
@@ -68,3 +68,20 @@ fn main() {
         }
     );
 }
+
+fn issue15559() {
+    fn foo() {}
+    assert_eq!(
+        //~^ unit_cmp
+        {
+            1;
+        },
+        foo()
+    );
+    assert_eq!(foo(), foo());
+    //~^ unit_cmp
+
+    // don't lint on explicitly written unit expr
+    assert_eq!(foo(), ());
+    assert_ne!((), ContainsUnit(()).0);
+}
diff --git a/tests/ui/unit_cmp.stderr b/tests/ui/unit_cmp.stderr
index 8f26749fd86..21aa9dce151 100644
--- a/tests/ui/unit_cmp.stderr
+++ b/tests/ui/unit_cmp.stderr
@@ -71,5 +71,23 @@ LL | |             true;
 LL | |     );
    | |_____^
 
-error: aborting due to 6 previous errors
+error: `assert_eq` of unit values detected. This will always succeed
+  --> tests/ui/unit_cmp.rs:74:5
+   |
+LL | /     assert_eq!(
+LL | |
+LL | |         {
+LL | |             1;
+LL | |         },
+LL | |         foo()
+LL | |     );
+   | |_____^
+
+error: `assert_eq` of unit values detected. This will always succeed
+  --> tests/ui/unit_cmp.rs:81:5
+   |
+LL |     assert_eq!(foo(), foo());
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 8 previous errors