fix: diagnostic for casting reference to slice

fixes: #118790

2 files changed, 27 insertions, 0 deletions

diff --git a/tests/ui/cast/cast-to-slice.rs b/tests/ui/cast/cast-to-slice.rs
new file mode 100644
index 00000000000..a6c784a3d47
--- /dev/null
+++ b/tests/ui/cast/cast-to-slice.rs
@@ -0,0 +1,8 @@
+fn main() {
+    "example".as_bytes() as [char];
+    //~^ ERROR cast to unsized type
+
+    let arr: &[u8] = &[0, 2, 3];
+    arr as [char];
+    //~^ ERROR cast to unsized type
+}
diff --git a/tests/ui/cast/cast-to-slice.stderr b/tests/ui/cast/cast-to-slice.stderr
new file mode 100644
index 00000000000..340c9c48859
--- /dev/null
+++ b/tests/ui/cast/cast-to-slice.stderr
@@ -0,0 +1,19 @@
+error[E0620]: cast to unsized type: `&[u8]` as `[char]`
+  --> $DIR/cast-to-slice.rs:2:5
+   |
+LL |     "example".as_bytes() as [char]; 
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^------
+   |                             |
+   |                             help: try casting to a reference instead: `&[char]`
+
+error[E0620]: cast to unsized type: `&[u8]` as `[char]`
+  --> $DIR/cast-to-slice.rs:6:5
+   |
+LL |     arr as [char];
+   |     ^^^^^^^------
+   |            |
+   |            help: try casting to a reference instead: `&[char]`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0620`.