Fix incorrect type narrowing to *NEVER* for array after foreach assignment

- Added hasOffsetValueType check in AssignHandler to prevent using setExistingOffsetValueType when offset is known to not exist in the array
- When the offset definitely doesn't exist (hasOffsetValueType returns no), fall through to setOffsetValueType which correctly widens the key type
- Updated bug-13270b-php8 test expectation to reflect more precise type inference (hasOffsetValue instead of hasOffset)
- New regression test in tests/PHPStan/Analyser/nsrt/bug-13786.php

Author: VincentLanglet

src/Analyser/ExprHandler/AssignHandler.php

@@ -991,6 +991,7 @@ private function produceArrayDimFetchAssignValueToWrite(array $dimFetchStack, ar
 				$offsetType !== null
 				&& $arrayDimFetch !== null
 				&& $scope->hasExpressionType($arrayDimFetch)->yes()
+				&& !$offsetValueType->hasOffsetValueType($offsetType)->no()
 			) {
 				$hasOffsetType = null;
 				if ($offsetType instanceof ConstantStringType || $offsetType instanceof ConstantIntegerType) {

tests/PHPStan/Analyser/nsrt/bug-13270b-php8.php

@@ -19,7 +19,7 @@ public function parseData(array $data): array
 			if (!array_key_exists('priceWithVat', $data['price'])) {
 				$data['price']['priceWithVat'] = null;
 			}
-			assertType("non-empty-array&hasOffset('priceWithVat')", $data['price']);
+			assertType("non-empty-array&hasOffsetValue('priceWithVat', mixed)", $data['price']);
 			if (!array_key_exists('priceWithoutVat', $data['price'])) {
 				$data['price']['priceWithoutVat'] = null;
 			}

tests/PHPStan/Analyser/nsrt/bug-13786.php

@@ -0,0 +1,20 @@
+<?php declare(strict_types=1);
+
+namespace Bug13786;
+
+use function PHPStan\Testing\assertType;
+
+/** @var array<mixed> $arr */
+
+/** @var non-empty-list<'a'|'b'|'c'> $cols */
+
+$total = [ ];
+foreach ($arr as $id => $dummy) {
+    $total[$id] = [ ];
+    foreach ($cols as $col) {
+        $total[$id][$col] = '0';
+    }
+    assertType("non-empty-array<'a'|'b'|'c'|'d', '0'>", $total[$id]);
+    $total[$id]['d'] = '0';
+    assertType("non-empty-array<'a'|'b'|'c'|'d', '0'>&hasOffsetValue('d', '0')", $total[$id]);
+}