> This approximates `if` statements being an expression that returns something.

Do you care to elaborate? "if (...) return ...;" looks closer to an expression for me:

  export function extractSearchToken(completionToken: { token: string; isQuoted?: boolean }): string {
    if (completionToken.isQuoted) return completionToken.token.slice(2).replace(/"$/, '');

    if (completionToken.token.startsWith('@')) return completionToken.token.substring(1);

    return completionToken.token;
  }