error[E0381]: assign to part of possibly-uninitialized variable: `t`
  --> $DIR/issue-54499-field-mutation-marks-mut-as-used.rs:12:9
   |
LL |         t.0 = S(1);
   |         ^^^^^^^^^^ use of possibly-uninitialized `t`

error[E0381]: assign to part of possibly-uninitialized variable: `u`
  --> $DIR/issue-54499-field-mutation-marks-mut-as-used.rs:20:9
   |
LL |         u.0 = S(1);
   |         ^^^^^^^^^^ use of possibly-uninitialized `u`

error[E0381]: assign to part of possibly-uninitialized variable: `v`
  --> $DIR/issue-54499-field-mutation-marks-mut-as-used.rs:28:9
   |
LL |         v.x = S(1);
   |         ^^^^^^^^^^ use of possibly-uninitialized `v`

error: aborting due to 3 previous errors

For more information about this error, try `rustc --explain E0381`.