Error Handling

Tea treats recoverable failures as typed values. You declare error variants up front, throw them from functions that advertise failure, and recover with catch plus case arms.

Typed errors and throws

Start by naming the failure cases a function can produce. That keeps the error surface explicit and makes it clear to callers what can go wrong.

error ConfigError {
  Missing(key: String)
}

def require_env(key: String) -> String ! ConfigError.Missing
  const value = @env(key)

  if value == nil
    throw ConfigError.Missing(key)
  end

  value!
end

Recover errors as values

When you want to turn an error into a regular value, catch it and match the specific variants you care about. Any unmatched path can fall through to a final wildcard arm.

def describe(path: String) -> String
  try read(path) catch err
    case is DataError.Missing
      `missing:${err.path}`
    case is DataError.Permission
      "denied"
    case _
      "unexpected"
  end
end