error: unclosed frontmatter
  --> $DIR/frontmatter-whitespace-2.rs:1:1
   |
LL | / ---cargo
...  |
LL | |
   | |_^
   |
note: frontmatter opening here was not closed
  --> $DIR/frontmatter-whitespace-2.rs:1:1
   |
LL | ---cargo
   | ^^^

warning: use of a double negation
  --> $DIR/frontmatter-whitespace-2.rs:9:6
   |
LL |     ---x
   |      ^^^
   |
   = note: the prefix `--` could be misinterpreted as a decrement operator which exists in other languages
   = note: use `-= 1` if you meant to decrement the value
   = note: `#[warn(double_negations)]` on by default
help: add parentheses for clarity
   |
LL |     --(-x)
   |       +  +

error: aborting due to 1 previous error; 1 warning emitted