Make sure array length diagnostic doesn't regress

Author: varkor

src/test/ui/consts/const-array-oob-arith.rs

@@ -4,8 +4,12 @@ const ARR: [i32; 6] = [42, 43, 44, 45, 46, 47];
 const IDX: usize = 3;
 const VAL: i32 = ARR[IDX];
 const BONG: [i32; (ARR[0] - 41) as usize] = [5];
-const BLUB: [i32; (ARR[0] - 40) as usize] = [5]; //~ ERROR: mismatched types
-const BOO: [i32; (ARR[0] - 41) as usize] = [5, 99]; //~ ERROR: mismatched types
+const BLUB: [i32; (ARR[0] - 40) as usize] = [5];
+//~^ ERROR: mismatched types
+//~| expected an array with a fixed size of 2 elements, found one with 1 element
+const BOO: [i32; (ARR[0] - 41) as usize] = [5, 99];
+//~^ ERROR: mismatched types
+//~| expected an array with a fixed size of 1 element, found one with 2 elements
 
 fn main() {
     let _ = VAL;

src/test/ui/consts/const-array-oob-arith.stderr

@@ -8,7 +8,7 @@ LL | const BLUB: [i32; (ARR[0] - 40) as usize] = [5];
               found type `[i32; 1]`
 
 error[E0308]: mismatched types
-  --> $DIR/const-array-oob-arith.rs:8:44
+  --> $DIR/const-array-oob-arith.rs:10:44
    |
 LL | const BOO: [i32; (ARR[0] - 41) as usize] = [5, 99];
    |                                            ^^^^^^^ expected an array with a fixed size of 1 element, found one with 2 elements