add array_first and array_last return type extensions

Author: canvural

src/Type/Php/ArrayFirstDynamicReturnTypeExtension.php

@@ -0,0 +1,48 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Type\Php;
+
+use PhpParser\Node\Expr\FuncCall;
+use PHPStan\Analyser\Scope;
+use PHPStan\DependencyInjection\AutowiredService;
+use PHPStan\Reflection\FunctionReflection;
+use PHPStan\Type\DynamicFunctionReturnTypeExtension;
+use PHPStan\Type\NullType;
+use PHPStan\Type\Type;
+use PHPStan\Type\TypeCombinator;
+use function count;
+
+#[AutowiredService]
+final class ArrayFirstDynamicReturnTypeExtension implements DynamicFunctionReturnTypeExtension
+{
+
+	public function isFunctionSupported(FunctionReflection $functionReflection): bool
+	{
+		return $functionReflection->getName() === 'array_first' && $functionReflection->isBuiltin();
+	}
+
+	public function getTypeFromFunctionCall(FunctionReflection $functionReflection, FuncCall $functionCall, Scope $scope): ?Type
+	{
+		$args = $functionCall->getArgs();
+
+		if (count($args) < 1) {
+			return null;
+		}
+
+		$argType = $scope->getType($args[0]->value);
+		$iterableAtLeastOnce = $argType->isIterableAtLeastOnce();
+
+		if ($iterableAtLeastOnce->no()) {
+			return new NullType();
+		}
+
+		$valueType = $argType->getFirstIterableValueType();
+
+		if ($iterableAtLeastOnce->yes()) {
+			return $valueType;
+		}
+
+		return TypeCombinator::union($valueType, new NullType());
+	}
+
+}

src/Type/Php/ArrayLastDynamicReturnTypeExtension.php

@@ -0,0 +1,48 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Type\Php;
+
+use PhpParser\Node\Expr\FuncCall;
+use PHPStan\Analyser\Scope;
+use PHPStan\DependencyInjection\AutowiredService;
+use PHPStan\Reflection\FunctionReflection;
+use PHPStan\Type\DynamicFunctionReturnTypeExtension;
+use PHPStan\Type\NullType;
+use PHPStan\Type\Type;
+use PHPStan\Type\TypeCombinator;
+use function count;
+
+#[AutowiredService]
+final class ArrayLastDynamicReturnTypeExtension implements DynamicFunctionReturnTypeExtension
+{
+
+	public function isFunctionSupported(FunctionReflection $functionReflection): bool
+	{
+		return $functionReflection->getName() === 'array_last' && $functionReflection->isBuiltin();
+	}
+
+	public function getTypeFromFunctionCall(FunctionReflection $functionReflection, FuncCall $functionCall, Scope $scope): ?Type
+	{
+		$args = $functionCall->getArgs();
+
+		if (count($args) < 1) {
+			return null;
+		}
+
+		$argType = $scope->getType($args[0]->value);
+		$iterableAtLeastOnce = $argType->isIterableAtLeastOnce();
+
+		if ($iterableAtLeastOnce->no()) {
+			return new NullType();
+		}
+
+		$valueType = $argType->getLastIterableValueType();
+
+		if ($iterableAtLeastOnce->yes()) {
+			return $valueType;
+		}
+
+		return TypeCombinator::union($valueType, new NullType());
+	}
+
+}

tests/PHPStan/Analyser/nsrt/array_first_last.php

@@ -0,0 +1,22 @@
+<?php // lint >= 8.5
+
+namespace ArrayFirstLast;
+
+use function PHPStan\Testing\assertType;
+
+/**
+ * @param string[] $stringArray
+ * @param non-empty-array<int, string> $nonEmptyArray
+ */
+function doFoo(array $stringArray, array $nonEmptyArray, $mixed): void
+{
+	assertType("'a'", array_first([1 => 'a', 0 => 'b', 2 => 'c']));
+	assertType('string|null', array_first($stringArray));
+	assertType('string', array_first($nonEmptyArray));
+	assertType('mixed', array_first($mixed));
+
+	assertType("'c'", array_last([1 => 'a', 0 => 'b', 2 => 'c']));
+	assertType('string|null', array_last($stringArray));
+	assertType('string', array_last($nonEmptyArray));
+	assertType('mixed', array_last($mixed));
+}