error[E0317]: `if` may be missing an `else` clause
  --> $DIR/issue-66387-if-without-else.rs:3:5
   |
LL | /     if true {
LL | |         return 0;
LL | |     }
   | |_____^ expected `i32`, found `()`
   |
   = note: `if` expressions without `else` evaluate to `()`
   = help: consider adding an `else` block that evaluates to the expected type

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0317`.