Change yield interpolation behaviour

Hello Internals! At the moment, there is a feature/bug in the PHP that allows to use interpolation of generators.

$code = <<<EXAMPLE

    Hello ${yield}

EXAMPLE;

I suspect that initially this functionality was not thought out, but it partially works, which allows you to implement useful functionality.

[$query, $params] = sql(fn() => <<<SQL

    SELECT * FROM users WHERE id = ${yield 42} OR id = ${yield 0xDEADBEEF}

SQL);

// Expected
// $query = "SELECT * FROM users WHERE id = ? OR id = ?"
// $params = [ 42, 0xDEADBEEF ]

When I say that the functionality was not thought out initially, I mean the behavior of generators within strings. For example, the following code, which should (seemingly) implement this functionality:

function sql(\Closure $expr)

{

    [$generator, $params] = [$expr(), $params];

    while ($generator->valid()) {

       $params[] = $generator->current(); // Get the value from "yield"

       $generator->send('?'); // Insert placeholder

    }

    return [$generator->getReturn()];

}

Causes an error:

Warning: Undefined variable $?

That is, the expression "${yield 42}" expects back not the result of this expression, but the name of the variable. Therefore, a complete and workable implementation of such a functionality is as follows: https://gist.github.com/SerafimArts/2e7702620480fbce6c24bc87bfb9cb0e I think it makes sense to do something about it. I have two suggestions: 1) Forbid using "yield" inside strings 2) Expect not a variable name as a result of this expression, but a substitution value. What do you think?