Added regression test

Author: staabm

tests/PHPStan/Rules/Arrays/NonexistentOffsetInArrayDimFetchRuleTest.php

@@ -1017,4 +1017,11 @@ public function testBug13538(): void
 		]);
 	}
 
+	public function testBug12805(): void
+	{
+		$this->reportPossiblyNonexistentGeneralArrayOffset = true;
+
+		$this->analyse([__DIR__ . '/data/bug-12805.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Arrays/data/bug-12805.php

@@ -0,0 +1,23 @@
+<?php declare(strict_types = 1);
+
+namespace Bug12805;
+
+/**
+ * @param array<string, array{ rtx?: int }> $operations
+ * @return array<string, array{ rtx: int }>
+ */
+function bug(array $operations): array {
+	$base = [];
+
+	foreach ($operations as $operationName => $operation) {
+		if (!isset($base[$operationName])) {
+			$base[$operationName] = [];
+		}
+		if (!isset($base[$operationName]['rtx'])) {
+			$base[$operationName]['rtx'] = 0;
+		}
+		$base[$operationName]['rtx'] += $operation['rtx'] ?? 0;
+	}
+
+	return $base;
+}