Fix intersecting array shapes with different optional keys

Author: rvanvelzen

src/Type/TypeCombinator.php

@@ -987,7 +987,7 @@ public static function intersect(Type ...$types): Type
 							$newArray->setOffsetValueType(
 								self::intersect($keyType, $types[$j]->getIterableKeyType()),
 								self::intersect($valueTypes[$k], $types[$j]->getIterableValueType()),
-								$types[$i]->isOptionalKey($k),
+								$types[$i]->isOptionalKey($k) && !$types[$j]->hasOffsetValueType($keyType)->yes(),
 							);
 						}
 						$types[$i] = $newArray->getArray();
@@ -1003,7 +1003,7 @@ public static function intersect(Type ...$types): Type
 							$newArray->setOffsetValueType(
 								self::intersect($keyType, $types[$i]->getIterableKeyType()),
 								self::intersect($valueTypes[$k], $types[$i]->getIterableValueType()),
-								$types[$j]->isOptionalKey($k),
+								$types[$j]->isOptionalKey($k) && !$types[$i]->hasOffsetValueType($keyType)->yes(),
 							);
 						}
 						$types[$j] = $newArray->getArray();

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -1129,6 +1129,7 @@ public function dataFileAsserts(): iterable
 		yield from $this->gatherAssertTypes(__DIR__ . '/../Rules/Variables/data/bug-8113.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/phpunit-integration.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-8361.php');
+		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-8373.php');
 	}
 
 	/**

tests/PHPStan/Analyser/data/bug-8373.php

@@ -0,0 +1,19 @@
+<?php declare(strict_types = 1);
+
+namespace Bug8373;
+
+use function PHPStan\Testing\assertType;
+
+function (string $one, string $two): string {
+	$args = [$one, $two];
+
+	assertType('array{string, string}', $args);
+	assertType('array{0?: non-falsy-string, 1?: non-falsy-string}', array_filter($args));
+
+	\assert(array_filter($args) === $args);
+
+	assertType('array{non-falsy-string, non-falsy-string}', $args);
+	assertType('array{non-falsy-string, non-falsy-string}', array_filter($args));
+
+	return $args[1];
+};