3 files changed, 70 insertions, 2 deletions
diff --git a/src/test/ui/macros/concat-bytes-error.rs b/src/test/ui/macros/concat-bytes-error.rs
index 9b4a9c2cf81..2c7997d5e59 100644
--- a/src/test/ui/macros/concat-bytes-error.rs
+++ b/src/test/ui/macros/concat-bytes-error.rs
@@ -39,4 +39,12 @@ fn main() {
     ]);
     concat_bytes!(5u16); //~ ERROR cannot concatenate numeric literals
     concat_bytes!([5u16]); //~ ERROR numeric literal is not a `u8`
+    concat_bytes!([3; ()]); //~ ERROR repeat count is not a number
+    concat_bytes!([3; -2]); //~ ERROR repeat count is not a number
+    concat_bytes!([pie; -2]); //~ ERROR repeat count is not a number
+    concat_bytes!([pie; 2]); //~ ERROR expected a byte literal
+    concat_bytes!([2.2; 0]); //~ ERROR cannot concatenate float literals
+    concat_bytes!([5.5; ()]); //~ ERROR repeat count is not a number
+    concat_bytes!([[1, 2, 3]; 3]); //~ ERROR cannot concatenate doubly nested array
+    concat_bytes!([[42; 2]; 3]); //~ ERROR cannot concatenate doubly nested array
 }
diff --git a/src/test/ui/macros/concat-bytes-error.stderr b/src/test/ui/macros/concat-bytes-error.stderr
index 1fc2d5c4843..f0c53839b3a 100644
--- a/src/test/ui/macros/concat-bytes-error.stderr
+++ b/src/test/ui/macros/concat-bytes-error.stderr
@@ -127,5 +127,55 @@ error: numeric literal is not a `u8`
 LL |     concat_bytes!([5u16]);
    |                    ^^^^
 
-error: aborting due to 20 previous errors
+error: repeat count is not a number
+  --> $DIR/concat-bytes-error.rs:42:23
+   |
+LL |     concat_bytes!([3; ()]);
+   |                       ^^
+
+error: repeat count is not a number
+  --> $DIR/concat-bytes-error.rs:43:23
+   |
+LL |     concat_bytes!([3; -2]);
+   |                       ^^
+
+error: repeat count is not a number
+  --> $DIR/concat-bytes-error.rs:44:25
+   |
+LL |     concat_bytes!([pie; -2]);
+   |                         ^^
+
+error: expected a byte literal
+  --> $DIR/concat-bytes-error.rs:45:20
+   |
+LL |     concat_bytes!([pie; 2]);
+   |                    ^^^
+   |
+   = note: only byte literals (like `b"foo"`, `b's'`, and `[3, 4, 5]`) can be passed to `concat_bytes!()`
+
+error: cannot concatenate float literals
+  --> $DIR/concat-bytes-error.rs:46:20
+   |
+LL |     concat_bytes!([2.2; 0]);
+   |                    ^^^
+
+error: repeat count is not a number
+  --> $DIR/concat-bytes-error.rs:47:25
+   |
+LL |     concat_bytes!([5.5; ()]);
+   |                         ^^
+
+error: cannot concatenate doubly nested array
+  --> $DIR/concat-bytes-error.rs:48:20
+   |
+LL |     concat_bytes!([[1, 2, 3]; 3]);
+   |                    ^^^^^^^^^
+
+error: cannot concatenate doubly nested array
+  --> $DIR/concat-bytes-error.rs:49:20
+   |
+LL |     concat_bytes!([[42; 2]; 3]);
+   |                    ^^^^^^^
+
+error: aborting due to 28 previous errors
 
diff --git a/src/test/ui/macros/concat-bytes.rs b/src/test/ui/macros/concat-bytes.rs
index 5415cf3fe22..fd8f99417ec 100644
--- a/src/test/ui/macros/concat-bytes.rs
+++ b/src/test/ui/macros/concat-bytes.rs
@@ -3,5 +3,15 @@
 
 fn main() {
     assert_eq!(concat_bytes!(), &[]);
-    assert_eq!(concat_bytes!(b'A', b"BC", [68, b'E', 70]), b"ABCDEF");
+    assert_eq!(
+        concat_bytes!(b'A', b"BC", [68, b'E', 70], [b'G'; 1], [72; 2], [73u8; 3], [65; 0]),
+        b"ABCDEFGHHIII",
+    );
+    assert_eq!(
+        concat_bytes!(
+            concat_bytes!(b"AB", b"CD"),
+            concat_bytes!(b"EF", b"GH"),
+        ),
+        b"ABCDEFGH",
+    );
 }