Updated E0527 to new error format

* Closes rust-lang#36113

src/librustc_typeck/check/_match.rs

@@ -233,9 +233,12 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
  let min_len = before.len() + after.len();
  if slice.is_none() {
  if min_len != size {
- span_err!(tcx.sess, pat.span, E0527,
- "pattern requires {} elements but array has {}",
- min_len, size);
+ struct_span_err!(
+ tcx.sess, pat.span, E0527,
+ "pattern requires {} elements but array has {}",
+ min_len, size)
+ .span_label(pat.span, &format!("expected {} elements",size))
+ .emit();
  }
  (inner_ty, tcx.types.err)
  } else if let Some(rest) = size.checked_sub(min_len) {

src/test/compile-fail/E0527.rs

@@ -13,7 +13,9 @@
 fn main() {
  let r = &[1, 2, 3, 4];
  match r {
- &[a, b] => { //~ ERROR E0527
+ &[a, b] => {
+ //~^ ERROR E0527
+ //~| NOTE expected 4 elements
  println!("a={}, b={}", a, b);
  }
  }