Error effects handling

Raising errors

Throwing errors is a simple message for error object

err = Error1 text: "Important error information ^_^"
err throw

Defining custom errors

The same as unions:

errordomain MyError =
| Error1 text: String
| Error2 code: Int

Catching

x = "text.txt" reatContent ifError: [
    "got some error!!!" echo
    | it
    | Error1 => it text echo
    "default value"
]

Defining possible errors in return type

Errors are effects that poison call stack.
Its kinda errors as values + exception in one thing.

They are explicit in methods signature: -> Int!Error or -> Int![Error1 Error2]
You don't always need to catch them, they will go further up stuck until caught
You can force catching all possible errors if you define empty errors list: -> Int![]

If method can throw error you need to mark its return type other-vice it will be a compile time error.
// TODO screenshot of such error

// ERROR not all possible errors mentioned use "-> Int!Error1"
Int sus -> Int = [ 
  Error1 text: "qwf" |> throw
]

If you lazy you can use just !, like -> Int!.
That's means any type of error, correct type will be inferred anyway, you just wont see it in signature

Int sas2 -> Int! = [
    x = Error2 code: 42
    ^ this != 0 => x throw |=> 1
]

Exhaustiveness

If there more than one error you need to check them all, same as union matching:

Int dangerous -> Int![Error1 Error2] = [
    Error1 text: "abc" |> throw
    Error2 code: -1 |> throw
    ^ 42
]

result = 42 dangerous ifError: [
    | it
    | Error1 => [ "oups" echo ]  
    // ERROR not all possible errors processed: Error2
]

Default value

You can ignore matching and just define default value:

x = "text.txt" reatContent ifError: [ "default value" ]

Full example

errordomain MyError =
| Error1 text: String
| Error2 code: Int

Int sas2 -> Int! = [
    x = Error2 code: 42
    x throw
    ^ this != 0 => x throw |=> 1
]

Int sas -> Int!Error1 = [
    x = Error1 text: "Important error information ^_^"
    ^ this != 0 => x throw |=> 1
]

// catch error
Int sus -> Int = [
    y = 1 sas ifError: [
        "got some error!!!" echo
        | it
        | Error1 => it text echo
        42
    ]
    y echo // 42
    ^3
]

// ignore error
Int sus2 -> Int! = [
    ^5 sus
]

1 sus

Last modified: 21 July 2024