Add test for error message

src/test/ui/slice-to-vec-comparison.rs

@@ -0,0 +1,6 @@
+fn main() {
+ let a = &[];
+ let b: &Vec<u8> = &vec![];
+ a > b;
+ //~^ ERROR mismatched types
+}

src/test/ui/slice-to-vec-comparison.stderr

@@ -0,0 +1,12 @@
+error[E0308]: mismatched types
+ --> $DIR/slice-to-vec-comparison.rs:4:9
+ |
+LL | a > b;
+ | ^ expected array of 0 elements , found struct `Vec`
+ |
+ = note: expected reference `&[_; 0]`
+ found reference `&Vec<u8>`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.