unnecessary_brace_in_string_interps

Unnecessary braces in a string interpolation.

The analyzer produces this diagnostic when a string interpolation with braces is used to interpolate a simple identifier and isn't followed by alphanumeric text.

The following code produces this diagnostic because the interpolation element ${s} uses braces when they are not necessary:

String f(String s) {
  return '"${s}"';
}

Remove the unnecessary braces:

String f(String s) {
  return '"$s"';
}