

HiddenGeneratorReturn

Emitted when a generator returns a value, but its declared return type (iterable, Iterator, Traversable, …) doesn't mention Generator, so the value can't be read back through the declared type.

<?php

/** @return iterable<int, string> */
function gen(): iterable {
    yield 'a';
    return 1; // HiddenGeneratorReturn
}

Why this is bad

A function containing yield always returns a Generator. The value of return is only reachable with Generator::getReturn(), which callers can't use on an iterable.

How to fix

Declare a Generator return type, whose fourth template parameter is the type of the returned value:

<?php

/** @return Generator<int, string, mixed, int> */
function gen(): Generator {
    yield 'a';
    return 1; // no issue
}

Or remove the returned value (return; and return null; are not reported).