error: format argument must be a string literal
  --> $DIR/issue-86865.rs:4:14
   |
LL |     println!(b"foo");
   |              -^^^^^
   |              |
   |              help: consider removing the leading `b`

error: format argument must be a string literal
  --> $DIR/issue-86865.rs:8:15
   |
LL |     write!(s, b"foo{}", "bar");
   |               -^^^^^^^
   |               |
   |               help: consider removing the leading `b`

error: aborting due to 2 previous errors