Implement ArrayKeyFirstLastTypeSpecifyingExtension

src/Type/Php/ArrayKeyFirstLastTypeSpecifyingExtension.php

@@ -0,0 +1,59 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Type\Php;
+
+use PhpParser\Node\Expr\FuncCall;
+use PHPStan\Analyser\Scope;
+use PHPStan\Analyser\SpecifiedTypes;
+use PHPStan\Analyser\TypeSpecifier;
+use PHPStan\Analyser\TypeSpecifierAwareExtension;
+use PHPStan\Analyser\TypeSpecifierContext;
+use PHPStan\DependencyInjection\AutowiredService;
+use PHPStan\Reflection\FunctionReflection;
+use PHPStan\Type\Accessory\NonEmptyArrayType;
+use PHPStan\Type\FunctionTypeSpecifyingExtension;
+use function in_array;
+use function strtolower;
+
+#[AutowiredService]
+final class ArrayKeyFirstLastTypeSpecifyingExtension implements FunctionTypeSpecifyingExtension, TypeSpecifierAwareExtension
+{
+
+	private TypeSpecifier $typeSpecifier;
+
+	public function isFunctionSupported(
+		FunctionReflection $functionReflection,
+		FuncCall $node,
+		TypeSpecifierContext $context,
+	): bool
+	{
+		return in_array(strtolower($functionReflection->getName()), ['array_key_first', 'array_key_last'])
+			&& $context->true();
+	}
+
+	public function specifyTypes(
+		FunctionReflection $functionReflection,
+		FuncCall $node,
+		Scope $scope,
+		TypeSpecifierContext $context,
+	): SpecifiedTypes
+	{
+		$arrayArg = $node->getArgs()[0]->value ?? null;
+		if ($arrayArg === null) {
+			return new SpecifiedTypes();
+		}
+
+		return $this->typeSpecifier->create(
+			$arrayArg,
+			new NonEmptyArrayType(),
+			$context,
+			$scope,
+		);
+	}
+
+	public function setTypeSpecifier(TypeSpecifier $typeSpecifier): void
+	{
+		$this->typeSpecifier = $typeSpecifier;
+	}
+
+}

tests/PHPStan/Analyser/nsrt/bug-14081.php

@@ -0,0 +1,31 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace Bug14081;
+
+use function PHPStan\Testing\assertType;
+
+/** @param list<string> $array */
+function first(array $array): mixed
+{
+	if (($key = array_key_first($array))) {
+		assertType('int<1, max>', $key);
+		assertType('non-empty-list<string>', $array);
+		assertType('string', $array[$key]);
+		return $array[$key];
+	}
+	return null;
+}
+
+/** @param list<string> $array */
+function last(array $array): mixed
+{
+	if (($key = array_key_last($array))) {
+		assertType('int<1, max>', $key);
+		assertType('non-empty-list<string>', $array);
+		assertType('string', $array[$key]);
+		return $array[$key];
+	}
+	return null;
+}