Error Handling

Runtime faults are caught and mitigated gracefully via structured exception blocks.

Try-Catch-Finally Blocks

The error handling block uses try, catch [variable], finally, and finishes with end:

try
    let num = 1 / 0
catch error
    print("Caught an error: " + str(error))
finally
    print("Cleanup: This block always executes.")
end

Try-Finally (No Catch)

You can omit the catch block and just use try/finally for resource cleanup:

try
    let f = "file_handle"
    # use resource...
finally
    print("cleaned")
end

Try-Catch (Ignoring Error)

If you don't need the error variable, you can omit it and use catch end:

try
    file.delete("temp.txt")
catch end

Finally with Return

The finally block runs even when a return statement is executed in the try block:

fn testReturn()
    try
        return 42
    finally
        print("cleanup runs before return")
    end
end
print(testReturn()) # prints "cleanup runs before return" then 42

Nested Try-Catch Order

When nesting try-catch blocks, the inner catch handles the error first. If it re-throws, the outer catch handles it:

try
    try
        throw "inner error"
    catch e
        print("Inner caught: ${e}")
        throw e  # re-throw to outer
    end
catch e
    print("Outer caught: ${e}")
end

Throwing Exceptions

Raise custom errors using the throw keyword. You can throw simple strings or complex payload Maps:

fn validateAge(age)
    if age < 0
        throw {"error": "InvalidAge", "message": "Age cannot be negative"}
    end
end

try
    validateAge(-1)
catch err
    print("Error Code: " + err["error"]) # => InvalidAge
end