Overriding a field included with record-type-inclusion doesn't remove the default value closure for that particular field being overriden

[rdhananjaya]

Description:

type R0 record {
    int|string f = 1;
};

type R1 record {
    *R0;
    string f;
};

public function main() {
    R1 r1 = { f : "hello"};
}

This results in:

error: {ballerina/lang.map}InherentTypeViolation {"message":"invalid value for record field 'f': expected value of type 'string', found 'int'"}
        at $value$R0:R0$gen$.<init>(main.bal:2)
           main:main(main.bal:11)

Steps to reproduce:

Affected Versions:

OS, DB, other environment details and versions:

Related Issues (optional):

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[rdhananjaya]

The culprit for this issue is when we initialize R1, it automatically calling the init of referenced types.

import ballerina/io;
type R record {|
    int hello = inc();
|};

type RR record {|
    *R;
    int hello = inc();
|};

public function main() {
    R|RR rr = <RR>{ hello: 22};
    lock {
        io:println(i); // prints 2 [`inc` method have invoked twise, even when value for `hello` is given to  the constructor]
    }
}

isolated int i = 0;

isolated function inc() returns int {
    lock {
        i = i + 1;
        return i;
    }
}

[MaryamZi]

We desugar the initialization logic of all the fields into the generated init method of the record. This initializes all of the fields in the records for which default values have been specified.

With type inclusion, I believe including records call the init methods of the included records to initialize fields that are initialized in the included records. But this'll result in errors for examples like in the issue. Just removing the init call of the included record isn't an option because for some fields the default value will still come from the included record.

type R0 record {
    int|string f = 1;
    int? g = 1;
};

type R1 record {
    *R0;
    string f; 
    // g is initialized in R0
};

To properly support inclusion like in the example IMO we need to be able to selectively call the initialization logic for specific fields. We may need to introduce the concept of default value closures attached to each field.

[warunalakshitha]

ATM calling the included record types in it calls generated during codegen. We can set a skipped field set during included record initialization but might cause more issues if we try to do that at runtime. Perfect solution would be to have default value closure for each field as @MaryamZi said. So we can independently initialize each record.

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      - Reason/EngineeringMistake - The issue occurred due to a mistake made in the past.
      - Reason/Regression - The issue has introduced a regression.
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      - Reason/Complex - Issue occurred due to complex scenario.
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