code: function canSwapBetweenExpressionAndStatement(replacement) {
    if (this.key !== "body" || !this.parentPath.isArrowFunctionExpression()) {
      return false;
    }
  
    if (this.isExpression()) {
      return t.isBlockStatement(replacement);
    } else if (this.isBlockStatement()) {
      return t.isExpression(replacement);
    }
  
    return false;
  }
docs: This checks whether we are swapping an arrow function's body between an
  expression and a block statement (or vice versa).
  
  This is because arrow functions may implicitly return an expression, which
  is the same as containing a block statement.