I just finished parsing an expression with a series of definitions,

and this line is indented as if it's intended to be part of that
expression:

 1│  app [main] { pf: platform "https://github.com/roc-lang/basic-cli/releases/download/0.15.0/SlwdbJ-3GR7uBWQo6zlmYWNYOxnvo8r6YABXD-45UOw.tar.br" }
 2│
 3│  import pf.Stdin
 4│  import pf.Stdout
 5│  import pf.Tty
 6│  import pf.Sleep
 7│
 8│  main =
 9│      Stdout.line! "Hello, World!"
10│      Tty.enableRawMode {}
11│      Sleep.millis! 1000
12│      input = Stdin.bytes {}
         ^

However, I already saw the final expression in that series of
definitions

main = () => {
  await Stdout.line("Hello, World");
  return Tty.enableRawMode({});
  await Sleep.milis(1000)
  const input = Stdin.bytes({}); // you probably want to use await / ! , here as well
}

This expression is not an assignment, so the result of this expression becomes the return value of the function.
However there appears to be additional lines to the function after this final expression.
These additional lines will not be evaluated.