[Bug]: Inconsistent runtime error messages when trying to modify a readonly record field

[Thushara-Piyasekara]

Description

An error message inconsistency can be observed when keeping and removing an unused function. Since the existence and removal of a dead function should not affect the runtime, this behavior can be considered as inconsistent.

Steps to Reproduce

Run the following code snippet with bal run.

public function main() returns error? {
    check testFrozenAnyArrayElementUpdate();
}

function testFrozenAnyArrayElementUpdate() returns error? {
    Employee e1 = {name: "Em", id: 1000};
    int[] i = [1, 2];
    anydata[] i1 = [i, e1];
    anydata[] i2 = i1.cloneReadOnly();
    Employee e2 = check trap <Employee>i2[1];
    e2["name"] = "Zee";
    return ();
}

function testFrozenTupleUpdate() {
    Employee e1 = {name: "Em", id: 1000};
    [int, Employee] t1 = [1, e1];
    [int, Employee] t2 = t1.cloneReadOnly();
    Employee e2 = {name: "Zee", id: 1200};
    t2[1] = e2;
}

type Employee record {|
    int id;
    string name;
|};

You will get the following error,

error: {ballerina/lang.map}InherentTypeViolation {"message":"cannot update 'readonly' field 'name' in record of type 'test:(thushara_piyasekara/test:0:Employee & readonly)'"}
        at thushara_piyasekara.test.0:testFrozenAnyArrayElementUpdate(helloWorld.bal:27)
           thushara_piyasekara.test.0:main(helloWorld.bal:18)

Modify the source code as follows and run again. You can either comment or delete the lines.

public function main() returns error? {
    check testFrozenAnyArrayElementUpdate();
}

function testFrozenAnyArrayElementUpdate() returns error? {
    Employee e1 = {name: "Em", id: 1000};
    int[] i = [1, 2];
    anydata[] i1 = [i, e1];
    anydata[] i2 = i1.cloneReadOnly();
    Employee e2 = check trap <Employee>i2[1];
    e2["name"] = "Zee";
    return ();
}

// function testFrozenTupleUpdate() {
//     Employee e1 = {name: "Em", id: 1000};
//     [int, Employee] t1 = [1, e1];
//     [int, Employee] t2 = t1.cloneReadOnly();
//     Employee e2 = {name: "Zee", id: 1200};
//     t2[1] = e2;
// }

type Employee record {|
    int id;
    string name;
|};

You will get the following error message,

error: {ballerina/lang.map}InvalidUpdate {"message":"Invalid update of record field: modification not allowed on readonly value"}
        at thushara_piyasekara.test.0:testFrozenAnyArrayElementUpdate(helloWorld.bal:27)
           thushara_piyasekara.test.0:main(helloWorld.bal:18)

Affected Version(s)

Ballerina 2201.9.0 SNAPSHOT

OS, DB, other environment details and versions

No response

Related area

-> Runtime

Related issue(s) (optional)

No response

Suggested label(s) (optional)

No response

Suggested assignee(s) (optional)

No response

[Thushara-Piyasekara]

Turned out this error inconsistency was due to BFields of generated immutable BRecords not being marked with SymbolFlags.READONLY flag inside the ReadOnlyUtils class.

[github-actions]

This issue is NOT closed with a proper Reason/ label. Make sure to add proper reason label before closing. Please add or leave a comment with the proper reason label now.

      - Reason/EngineeringMistake - The issue occurred due to a mistake made in the past.
      - Reason/Regression - The issue has introduced a regression.
      - Reason/MultipleComponentInteraction - Issue occured due to interactions in multiple components.
      - Reason/Complex - Issue occurred due to complex scenario.
      - Reason/Invalid - Issue is invalid.
      - Reason/Other - None of the above cases.