error: mismatched closing delimiter: `]`
  --> $DIR/issue-81827.rs:10:23
   |
LL | fn r()->i{0|{#[cfg(r(0{]0
   |               -       ^^ mismatched closing delimiter
   |               |       |
   |               |       unclosed delimiter
   |               closing delimiter possibly meant for this

error: this file contains an unclosed delimiter
  --> $DIR/issue-81827.rs:10:27
   |
LL | fn r()->i{0|{#[cfg(r(0{]0
   |          -  -          - ^
   |          |  |          |
   |          |  |          missing open `[` for this delimiter
   |          |  unclosed delimiter
   |          unclosed delimiter

error: aborting due to 2 previous errors