Do not generalize big array when combined with empty array

Fixes phpstan/phpstan#10834

Author: RobertMe

src/Type/TypeCombinator.php

@@ -664,12 +664,19 @@ private static function processArrayTypes(array $arrayTypes): array
 		$valueTypesForGeneralArray = [];
 		$generalArrayOccurred = false;
 		$constantKeyTypesNumbered = [];
+		$filledArrays = 0;
+		$overflowed = false;
 
 		/** @var int|float $nextConstantKeyTypeIndex */
 		$nextConstantKeyTypeIndex = 1;
 
 		foreach ($arrayTypes as $arrayType) {
-			if ($generalArrayOccurred || !$arrayType->isConstantArray()->yes()) {
+			$isConstantArray = $arrayType->isConstantArray()->yes();
+			if (!$isConstantArray || !$arrayType->isIterableAtLeastOnce()->no()) {
+				$filledArrays++;
+			}
+
+			if ($generalArrayOccurred || !$isConstantArray) {
 				foreach ($arrayType->getArrays() as $type) {
 					$keyTypesForGeneralArray[] = $type->getIterableKeyType();
 					$valueTypesForGeneralArray[] = $type->getItemType();
@@ -693,13 +700,14 @@ private static function processArrayTypes(array $arrayTypes): array
 					$nextConstantKeyTypeIndex *= 2;
 					if (!is_int($nextConstantKeyTypeIndex)) {
 						$generalArrayOccurred = true;
+						$overflowed = true;
 						continue 2;
 					}
 				}
 			}
 		}
 
-		if ($generalArrayOccurred) {
+		if ($generalArrayOccurred && (!$overflowed || $filledArrays > 1)) {
 			$scopes = [];
 			$useTemplateArray = true;
 			foreach ($arrayTypes as $arrayType) {

tests/PHPStan/Analyser/NodeScopeResolverTest.php

@@ -1461,6 +1461,7 @@ public function dataFileAsserts(): iterable
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-10468.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-6613.php');
 		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-10187.php');
+		yield from $this->gatherAssertTypes(__DIR__ . '/data/bug-10834.php');
 	}
 
 	/**

tests/PHPStan/Analyser/data/bug-10834.php

@@ -0,0 +1,21 @@
+<?php
+
+declare(strict_types=1);
+
+use function PHPStan\Testing\assertType;
+
+/**
+ * @return array{1: string, 2: int, 3: bool, 4: string, 5: int, 6: bool, 7: string, 8: int, 9: bool, 10: string, 11: int, 12: bool, 13: string, 14: int, 15: bool, 16: string, 17: int, 18: bool, 19: string, 20: int, 21: bool, 22: string, 23: int, 24: bool, 25: string, 26: int, 27: bool, 28: string, 29: int, 30: bool, 31: string, 32: int, 33: bool, 34: string, 35: int, 36: bool, 37: string, 38: int, 39: bool, 40: string, 41: int, 42: bool, 43: string, 44: int, 45: bool, 46: string, 47: int, 48: bool, 49: string, 50: int, 51: bool, 52: string, 53: int, 54: bool, 55: string, 56: int, 57: bool, 58: string, 59: int, 60: bool, 61: string, 62: int, 63: bool, 64: float}|null
+ */
+function returnArrayOrNull()
+{
+	return null;
+}
+
+function test(): void {
+	$arrayOrNull = returnArrayOrNull();
+
+	assertType('array{1: string, 2: int, 3: bool, 4: string, 5: int, 6: bool, 7: string, 8: int, 9: bool, 10: string, 11: int, 12: bool, 13: string, 14: int, 15: bool, 16: string, 17: int, 18: bool, 19: string, 20: int, 21: bool, 22: string, 23: int, 24: bool, 25: string, 26: int, 27: bool, 28: string, 29: int, 30: bool, 31: string, 32: int, 33: bool, 34: string, 35: int, 36: bool, 37: string, 38: int, 39: bool, 40: string, 41: int, 42: bool, 43: string, 44: int, 45: bool, 46: string, 47: int, 48: bool, 49: string, 50: int, 51: bool, 52: string, 53: int, 54: bool, 55: string, 56: int, 57: bool, 58: string, 59: int, 60: bool, 61: string, 62: int, 63: bool, 64: float}|null', $arrayOrNull);
+	assertType('array{}|array{1: string, 2: int, 3: bool, 4: string, 5: int, 6: bool, 7: string, 8: int, 9: bool, 10: string, 11: int, 12: bool, 13: string, 14: int, 15: bool, 16: string, 17: int, 18: bool, 19: string, 20: int, 21: bool, 22: string, 23: int, 24: bool, 25: string, 26: int, 27: bool, 28: string, 29: int, 30: bool, 31: string, 32: int, 33: bool, 34: string, 35: int, 36: bool, 37: string, 38: int, 39: bool, 40: string, 41: int, 42: bool, 43: string, 44: int, 45: bool, 46: string, 47: int, 48: bool, 49: string, 50: int, 51: bool, 52: string, 53: int, 54: bool, 55: string, 56: int, 57: bool, 58: string, 59: int, 60: bool, 61: string, 62: int, 63: bool, 64: float}', $arrayOrNull ?? []);
+	assertType('array{}|array{1: string, 2: int, 3: bool, 4: string, 5: int, 6: bool, 7: string, 8: int, 9: bool, 10: string, 11: int, 12: bool, 13: string, 14: int, 15: bool, 16: string, 17: int, 18: bool, 19: string, 20: int, 21: bool, 22: string, 23: int, 24: bool, 25: string, 26: int, 27: bool, 28: string, 29: int, 30: bool, 31: string, 32: int, 33: bool, 34: string, 35: int, 36: bool, 37: string, 38: int, 39: bool, 40: string, 41: int, 42: bool, 43: string, 44: int, 45: bool, 46: string, 47: int, 48: bool, 49: string, 50: int, 51: bool, 52: string, 53: int, 54: bool, 55: string, 56: int, 57: bool, 58: string, 59: int, 60: bool, 61: string, 62: int, 63: bool, 64: float}|null', rand() ? $arrayOrNull : []);
+}