E0164 Update error format #35269

- Fixes #35269
- Part of #35233

r? @jonathandturner

src/librustc_typeck/check/_match.rs

@@ -574,7 +574,8 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                 tcx.sess.add_lint(lint::builtin::MATCH_OF_UNIT_VARIANT_VIA_PAREN_DOTDOT,
                                   pat.id, pat.span, msg);
             } else {
-                span_err!(tcx.sess, pat.span, E0164, "{}", msg);
+                struct_span_err!(tcx.sess, pat.span, E0164, "{}", msg)
+                    .span_label(pat.span, &format!("not a tuple variant or struct")).emit();
                 on_error();
             }
         };

src/test/compile-fail/E0164.rs

@@ -13,6 +13,7 @@ enum Foo { B { i: u32 } }
 fn bar(foo: Foo) -> u32 {
     match foo {
         Foo::B(i) => i, //~ ERROR E0164
+                        //~| NOTE not a tuple variant or struct
     }
 }