[Bug]: Can't use types that don't explicitly redefine strings field for raw template expressions

[heshanpadmasiri]

Description

For raw template expressions we can given a object type that includes object:RawTemplat with a narrower insertions field as the contextually expected type. However if that type in question don't explicitly override the strings field,

1. insertions and strings get mixed up
2. trying to print the object value causes NPE

This is potentionally an object type inclusion bug

Steps to Reproduce

Consider,

import ballerina/io;

type Template2 object {
    *object:RawTemplate;
    public (string[] & readonly) strings;
    public int[] insertions;
};

type Template1 object {
    *object:RawTemplate;
    public int[] insertions;
};

public function main() {
    Template2 v1 = `${1}, ${2}`;
    io:println(v1.insertions);
    io:println(v1.strings);

    Template1 v2 = `${1}, ${2}`;
    io:println(v2.insertions);
    io:println(v2.strings);
}

This results: (note insertions and strings are interchanged in second example)

[1,2]
["",", ",""]
["",", ",""]
[1,2]

This caues NPE:

import ballerina/io;

type Template1 object {
    *object:RawTemplate;
    public int[] insertions;
};

public function main() {
    Template1 v2 = `${1}, ${2}`;
    io:println(v2);
}

[2024-10-21 15:36:34,674] SEVERE {b7a.log.crash} - Cannot load from object array because "this.refValues" is null 
java.lang.NullPointerException: Cannot load from object array because "this.refValues" is null
	at io.ballerina.runtime.internal.values.ArrayValueImpl.getBString(ArrayValueImpl.java:456)
	at ballerina.io.1.$value$PrintableRawTemplateImpl.toString(print.bal:127)
	at ballerina.io.1.$value$PrintableRawTemplateImpl.call(print.bal)
	at ballerina.io.1.$value$PrintableClassImpl.toString(print.bal:107)
	at ballerina.io.1.$value$PrintableClassImpl.call(print.bal)
	at io.ballerina.runtime.internal.util.StringUtils.getStringVal(StringUtils.java:96)
	at io.ballerina.runtime.api.utils.StringUtils.getStringValue(StringUtils.java:173)
	at io.ballerina.stdlib.io.nativeimpl.PrintUtils.println(PrintUtils.java:69)
	at ballerina.io.1.print.externPrintln(print.bal:147)
	at ballerina.io.1.print.println(print.bal:65)
	at main.main(main.bal:10)
	at $_init.$moduleExecute(.)
	at $_init.$lambda$$moduleExecute$(.)
	at io.ballerina.runtime.internal.scheduling.SchedulerItem.execute(SchedulerItem.java:54)
	at io.ballerina.runtime.internal.scheduling.Scheduler.run(Scheduler.java:320)
	at io.ballerina.runtime.internal.scheduling.Scheduler.runSafely(Scheduler.java:287)
	at java.base/java.lang.Thread.run(Thread.java:840)

Affected Version(s)

Ballerina 2201.10.1 (Swan Lake Update 10)
Language specification 2024R1
Update Tool 1.4.3

OS, DB, other environment details and versions

No response

Related area

-> Runtime

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