WIP

Author: VincentLanglet

src/Type/Constant/ConstantArrayType.php

@@ -1840,18 +1840,31 @@ public function makeOffsetRequired(Type $offsetType): self
 	{
 		$offsetType = $offsetType->toArrayKey();
 		$optionalKeys = $this->optionalKeys;
+		$isList = $this->isList->yes();
 		foreach ($this->keyTypes as $i => $keyType) {
 			if (!$keyType->equals($offsetType)) {
 				continue;
 			}
 
+			$keyValue = $keyType->getValue();
 			foreach ($optionalKeys as $j => $key) {
-				if ($i === $key) {
+				if (
+					$i === $key
+					|| (
+						$isList
+						&& is_int($keyValue)
+						&& is_int($this->keyTypes[$key]->getValue())
+						&& $this->keyTypes[$key]->getValue() < $keyValue
+					)
+				) {
 					unset($optionalKeys[$j]);
-					return new self($this->keyTypes, $this->valueTypes, $this->nextAutoIndexes, array_values($optionalKeys), $this->isList);
 				}
 			}
 
+			if (count($this->optionalKeys) !== count($optionalKeys)) {
+				return new self($this->keyTypes, $this->valueTypes, $this->nextAutoIndexes, array_values($optionalKeys), $this->isList);
+			}
+
 			break;
 		}
 

tests/PHPStan/Analyser/nsrt/bug-14177.php

@@ -12,7 +12,7 @@ class HelloWorld
 	public function testList(array $b): void
 	{
 		if (array_key_exists(3, $b)) {
-			assertType('list{0: string, 1: string, 2?: string, 3: string}', $b);
+			assertType('array{string, string, string, string}', $b);
 		} else {
 			assertType('array{0: string, 1: string, 2?: string}', $b);
 		}

tests/PHPStan/Rules/Variables/IssetRuleTest.php

@@ -499,6 +499,22 @@ public function testPr4374(): void
 		]);
 	}
 
+	public function testIssetConstantArray(): void
+	{
+		$this->treatPhpDocTypesAsCertain = true;
+
+		$this->analyse([__DIR__ . '/data/isset-constant-array.php'], [
+			[
+				'Offset 2 on array{0: string, 1: string, 2: string, 3: string, 4?: string} in isset() always exists and is not nullable.',
+				13,
+			],
+			[
+				'Offset 3 on array{string, string, string, string, string} in isset() always exists and is not nullable.',
+				17,
+			],
+		]);
+	}
+
 	public function testBug10640(): void
 	{
 		$this->treatPhpDocTypesAsCertain = true;

tests/PHPStan/Rules/Variables/data/isset-constant-array.php

@@ -0,0 +1,22 @@
+<?php declare(strict_types = 1);
+
+namespace IssetConstantArray;
+
+class HelloWorld
+{
+	/**
+	 * @param list{0: string, 1: string, 2?: string, 3?: string, 4?: string} $list
+	 */
+	public function sayHello(array $list): bool
+	{
+		if (isset($list[3])) {
+			return isset($list[2]); // offset 3 implies offset 2;
+		}
+
+		if (isset($list[4])) {
+			return isset($list[3]); // offset 4 implies offset 3;
+		}
+
+		return false;
+	}
+}