[Php71] Skip AssignArrayToStringRector on a variable re-assigned as string

[TomasVotruba]

Main is red on AssignArrayToStringRectorTest, fixture skip_reassigned_as_string.php.inc. Not caused by any commit here — phpstan/phpstan 2.2.8 was released, and CI resolves it while a local vendor/ still on 2.2.7 stays green. Reproducible with composer update phpstan/phpstan.

2.2.8 infers a possibly undefined variable as ErrorType, where it used to report a union of its possible types. The rule leaned on that union:

if (empty($where)) {
    $where = '';           // native type of $where was array{}|''|null|…, now *ERROR*
} else {
    $where = 'WHERE ' . implode(' AND ', $where);
}

$sql = 'SELECT …' . $where;

Neither the isArray() nor the UnionType guard matches an ErrorType, so the empty string became an array and broke the concatenation below:

 if (empty($where)) {
-    $where = '';
+    $where = [];
 } else {
     $where = 'WHERE ' . implode(' AND ', $where);
 }

Guarding on ErrorType is not the fix — a first assignment like $string = ''; reports *ERROR* for the same reason, and those must keep converting.

What actually makes $where a string here is that it is assigned a string further down, so the rule now checks exactly that. An empty string assign does not count as proof, since it is itself a candidate for the same re-type — that keeps fixture.php.inc converting its second $string = '';.

Full suite green on 2.2.8: 5372 tests, 6884 assertions.

Second commit

SetManagerTest still expected 8 Twig composer-triggered sets. rectorphp/rector-symfony#1010 is merged, so TwigSetProvider now registers only its composer-based trigger — every rule of the per-version Twig sets is already in it, bound to the twig/twig version it needs. Folded in here so this PR is green on its own; it was #8294, now closed.