Intersection Types Cannot Be Used to Database Operations

[ThisaruGuruge]

Description:

If a database operation is used with readonly types, the type inferring fails with the following error:

Expected type to be \'(test:record {| string foo |} & readonly)\' but found \'record{}\'.

Use the following code:

import ballerina/sql;

final mysql:Client dbClient = check new (...);

type Foo readonly & record {
    string foo;   
};

isolated function getPosts(string? userId) returns stream<Foo, error?> {
    sql:ParameterizedQuery query = `SELECT * FROM post`;
    return dbClient->query(query);
}