How to achieve custom type narrowing in if block ?

[xiangnanscu]

---@alias Record {[string]: string|boolean|number}
---@class Sql
local Sql = {}
---@param self Sql
---@param row Record|Sql
---@return Sql
function Sql.new(self, row)
  if self:is_sql_type(row) then
    print(row) --how to narrow row to 'Sql' type here?
  else
  end
end

function Sql.is_sql_type(self, row)
  --some checking logic
  return true
end

function Sql.is_record_type(self, row)
  --some checking logic
  return true
end

[carsakiller]

You can use @cast

if something then
    ---@cast row sql
    print(row)
end