Error Methods

Errors in Risor are first-class values that carry diagnostic information about what went wrong and where. You can create error values with the error() built-in function and inspect them using the methods described here.

Method Reference

Creating Errors

Use the error() built-in to create an error value. This does not throw or halt execution. It simply returns an error as a value.

let err = error("something went wrong")
type(err)   // "error"

The error() function supports format arguments like sprintf:

let err = error("file not found: %s", "config.json")

Inspecting Errors

message

Return the error message as a string.

let err = error("something went wrong")
err.message()    // "something went wrong"

error

Alias for message(). Returns the error message as a string.

let err = error("something went wrong")
err.error()    // "something went wrong"

kind

Return the error kind as a string. The kind indicates the category of the error, such as "type", "value", or "error".

let err = error("something went wrong")
err.kind()    // e.g. "error"

line

Return the source line number where the error was created.

let err = error("oops")
err.line()    // e.g. 3

column

Return the source column number where the error was created.

let err = error("oops")
err.column()    // e.g. 11

filename

Return the source filename where the error was created.

let err = error("oops")
err.filename()    // e.g. "main.risor"

source

Return the source code context around where the error was created.

let err = error("oops")
err.source()    // source code snippet

stack

Return the full stack trace as a list of maps. Each map in the list contains the keys function, line, column, and filename. This is useful for debugging errors that propagate through multiple function calls.

let err = error("oops")
err.stack()    // e.g. [{"function": "main", "line": 1, "column": 11, "filename": "main.risor"}]

Example: Error Handling Pattern

Errors are commonly used with conditional checks to handle failure cases:

let result = some_operation()
 
if (type(result) == "error") {
    result.message()   // the error message
    result.line()      // source line number
    result.stack()     // stack trace
}