[Bug]: False positive return-check error when using match case accessing a JSON field

[mahimadesilva]

Description

When using a match expression on a JSON field inside a do { } on fail block, and each match case performs a return, the Ballerina compiler reports:

ERROR [main.bal:(134:1,134:2)] this function must return a result

This issue occurs even when a wildcard (_) case is included.

Steps to Reproduce

Reproducible Code:

public function doEval(json selectExpression) returns string|error {
    do {
        match selectExpression.key1 {
            "column" =>
            {
                return "c";
            }
            "select" =>
            {
                return "s";
            }
            _ =>
            {
                return "d";
            }

        }
    } on fail error err {
        return err;
    }
}

Affected Version(s)

Ballerina 2201.12.10 (Swan Lake Update 12)

OS, DB, other environment details and versions

Windows 10

Related area

-> Compilation

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