XO0157: `${}` with no expression

An interpolation must contain an expression whose type implements Display. ${} (or ${ }) has nothing to interpolate. Put an expression inside, or escape the dollar sign (\${}) to write the characters literally. See core 1.6.

Example

fn f() -> Str {
  "a ${}"
}

Fix

fn f() -> Str {
  "a \${}"
}

Run xo explain XO0157 for this text in a terminal, or see section 10.6 of the specification.