Narrow offset after isset() on list

Author: staabm

src/Rules/Arrays/AllowedArrayKeysTypes.php

@@ -71,6 +71,11 @@ public static function narrowOffsetKeyType(Type $varType, Type $keyType): ?Type
 			return $narrowedKey;
 		} elseif ($varIterableKeyType->isInteger()->yes() && $keyType->isString()->yes()) {
 			return TypeCombinator::intersect($varIterableKeyType->toString(), $keyType);
+		} elseif ($varType->isList()->yes()) {
+			return TypeCombinator::intersect(
+				$varIterableKeyType,
+				$keyType,
+			);
 		}
 
 		return new MixedType(

tests/PHPStan/Analyser/nsrt/bug-12274.php

@@ -92,9 +92,9 @@ function testShouldLooseListbyAst(array $list, int $i): void
 
 		assertType('list<int>', $list);
 		$list[1+$i] = 21;
-		assertType('non-empty-array<int, int>', $list);
+		assertType('non-empty-array<int<0, max>, int>', $list);
 	}
-	assertType('array<int, int>', $list);
+	assertType('array<int<0, max>, int>', $list);
 }
 
 /** @param list<int> $list */
@@ -103,7 +103,7 @@ function testShouldLooseListbyAst2(array $list, int $i): void
 	if (isset($list[$i])) {
 		assertType('list<int>', $list);
 		$list[2+$i] = 21;
-		assertType('non-empty-array<int, int>', $list);
+		assertType('non-empty-array<int<0, max>, int>', $list);
 	}
-	assertType('array<int, int>', $list);
+	assertType('array<int<0, max>, int>', $list);
 }

tests/PHPStan/Analyser/nsrt/bug-12933.php

@@ -0,0 +1,48 @@
+<?php // lint >= 8.0
+
+namespace Bug12933;
+
+use function PHPStan\Testing\assertType;
+
+/**
+ * @phpstan-type record array{id: positive-int, name: string}
+ */
+class Collection
+{
+	/** @param list<record> $list */
+	public function __construct(
+		public array $list
+	)
+	{
+	}
+
+	public function updateNameIsset(int $index, string $name): void
+	{
+		assert(isset($this->list[$index]));
+		assertType('int<0, max>', $index);
+	}
+
+	public function updateNameArrayKeyExists(int $index, string $name): void
+	{
+		assert(array_key_exists($index, $this->list));
+		assertType('int<0, max>', $index);
+	}
+
+	/**
+	 * @param int<-5, 5> $index
+	 */
+	public function issetNarrowsIntRange(int $index, string $name): void
+	{
+		assert(isset($this->list[$index]));
+		assertType('int<0, 5>', $index);
+	}
+
+	/**
+	 * @param int<5, 15> $index
+	 */
+	public function issetNotWidensIntRange(int $index, string $name): void
+	{
+		assert(isset($this->list[$index]));
+		assertType('int<5, 15>', $index);
+	}
+}