psalm/tests/fixtures/stubs/conditional_interface.php

<?php
if (interface_exists(Foo::class)) {
    interface I1 extends Foo
    {
    }
} else {
    interface I1
    {
    }
}

if (!interface_exists(Foo::class)) {
    interface I2
    {
    }
} else {
    interface I2 extends Foo
    {
    }
}

if (interface_exists('Bar')) {
    interface I3 extends Bar
    {
    }
} else {
    interface I3
    {
    }
}

if (!interface_exists('Bar')) {
    interface I4
    {
    }
} else {
    interface I4 extends Bar
    {
    }
}

if (interface_exists('Throwable')) {
    interface I5 extends Throwable
    {
    }
} else {
    interface I5
    {
    }
}

if (!interface_exists('Throwable')) {
    interface I6
    {
    }
} else {
    interface I6 extends Throwable
    {
    }
}

if (interface_exists(Throwable::class)) {
    interface I7 extends Throwable
    {
    }
} else {
    interface I7
    {
    }
}

if (!interface_exists(Throwable::class)) {
    interface I8
    {
    }
} else {
    interface I8 extends Throwable
    {
    }
}