Rollup merge of rust-lang#35644 - garekkream:update-E0302-new-error-f…

…ormat, r=jonathandturner

Update E0302 to the new format

Part of rust-lang#35233.
Fixes rust-lang#35523.

r? @jonathandturner

src/librustc_const_eval/check_match.rs

@@ -1187,7 +1187,9 @@ impl<'a, 'gcx, 'tcx> Delegate<'tcx> for MutationChecker<'a, 'gcx> {
  fn mutate(&mut self, _: NodeId, span: Span, _: cmt, mode: MutateMode) {
  match mode {
  MutateMode::JustWrite | MutateMode::WriteAndRead => {
- span_err!(self.cx.tcx.sess, span, E0302, "cannot assign in a pattern guard")
+ struct_span_err!(self.cx.tcx.sess, span, E0302, "cannot assign in a pattern guard")
+ .span_label(span, &format!("assignment in pattern guard"))
+ .emit();
  }
  MutateMode::Init => {}
  }

src/test/compile-fail/E0302.rs

@@ -12,6 +12,7 @@ fn main() {
  match Some(()) {
  None => { },
  option if { option = None; false } => { }, //~ ERROR E0302
+ //~| NOTE assignment in pattern guard
  Some(_) => { }
  }
 }