error: invalid format string: expected `'}'` but string was terminated
  --> $DIR/closing-brace-as-fill.rs:6:35
   |
LL |     println!("Hello, world! {0:}<3", 2);
   |                                -  ^ expected `'}'` in format string
   |                                |
   |                                this is not interpreted as a formatting closing brace
   |
   = note: the character `'}'` is interpreted as a fill character because of the `:` that precedes it

error: aborting due to previous error