Fix false positives on existing-offsets after assign

src/Analyser/NodeScopeResolver.php

@@ -5496,7 +5496,12 @@ private function processAssignVar(
 				}
 
 				if ($originalVar->dim instanceof Variable || $originalVar->dim instanceof Node\Scalar) {
-					if (!$scope->hasExpressionType($originalVar)->yes()) {
+					$currentVarType = $scope->getType($originalVar);
+					$currentVarNativeType = $scope->getNativeType($originalVar);
+					if (
+						!$originalValueToWrite->isSuperTypeOf($currentVarType)->yes()
+						|| !$originalNativeValueToWrite->isSuperTypeOf($currentVarNativeType)->yes()
+					) {
 						$scope = $scope->assignExpression(
 							$originalVar,
 							$originalValueToWrite,

tests/PHPStan/Rules/Arrays/NonexistentOffsetInArrayDimFetchRuleTest.php

@@ -856,6 +856,22 @@ public function testBug12406(): void
 		$this->analyse([__DIR__ . '/data/bug-12406.php'], []);
 	}
 
+	public function testBug12406b(): void
+	{
+		$this->reportPossiblyNonexistentGeneralArrayOffset = true;
+
+		$this->analyse([__DIR__ . '/data/bug-12406b.php'], [
+			[
+				'Offset int<0, max> might not exist on non-empty-list<array{0: string, 1: non-empty-string, 2: non-falsy-string, 3: numeric-string, 4?: numeric-string, 5?: numeric-string}>.',
+				22,
+			],
+			[
+				'Offset int<0, max> might not exist on non-empty-list<array{0: string, 1: non-empty-string, 2: non-falsy-string, 3: numeric-string, 4?: numeric-string, 5?: numeric-string}>.',
+				23,
+			],
+		]);
+	}
+
 	public function testBug11679(): void
 	{
 		$this->reportPossiblyNonexistentGeneralArrayOffset = true;

tests/PHPStan/Rules/Arrays/data/bug-12406b.php

@@ -0,0 +1,35 @@
+<?php
+
+namespace Bug12406_2;
+
+final class Foo
+{
+
+	public function sayHello(string $s): void
+	{
+		$stats = [];
+		preg_match_all('~
+			commit[ ][a-z0-9]{40}\\n
+			Author:\s+(.+)\s+<[^>]+>\\n
+			AuthorDate:[^\\n]+\\n
+			Commit:[^\\n]+\\n
+			CommitDate:[^\\n]+\\n\\n
+			(\s+(?:[^\n]+\n)+)\n
+			[ ](\\d+)[ ]files?[ ]changed,(?:[ ](\\d+)[ ]insertions?\\(\\+\\),?)?(?:[ ](\\d+)[ ]deletions?\\(-\\))?
+		~mx', $s, $matches, PREG_SET_ORDER);
+
+		for ($i = 0; $i < count($matches); $i++) {
+			$author = $matches[$i][1];
+			$files = (int) $matches[$i][3];
+			$insertions = (int) ($matches[$i][4] ?? 0);
+			$deletions = (int) ($matches[$i][5] ?? 0);
+
+			$stats[$author]['commits'] = ($stats[$author]['commits'] ?? 0) + 1;
+			$stats[$author]['files'] = ($stats[$author]['files'] ?? 0) + $files;
+			$stats[$author]['insertions'] = ($stats[$author]['insertions'] ?? 0) + $insertions;
+			$stats[$author]['deletions'] = ($stats[$author]['deletions'] ?? 0) + $deletions;
+			$stats[$author]['diff'] = ($stats[$author]['diff'] ?? 0) + $insertions - $deletions;
+		}
+	}
+
+}