Introduce StrrevFunctionReturnTypeExtension

conf/config.neon

@@ -1774,6 +1774,11 @@ services:
 		tags:
 			- phpstan.broker.dynamicFunctionReturnTypeExtension
 
+	-
+		class: PHPStan\Type\Php\StrrevFunctionReturnTypeExtension
+		tags:
+			- phpstan.broker.dynamicFunctionReturnTypeExtension
+
 	-
 		class: PHPStan\Type\Php\SubstrDynamicReturnTypeExtension
 		tags:

src/Type/Php/StrrevFunctionReturnTypeExtension.php

@@ -0,0 +1,73 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Type\Php;
+
+use PhpParser\Node\Expr\FuncCall;
+use PHPStan\Analyser\Scope;
+use PHPStan\Reflection\FunctionReflection;
+use PHPStan\Type\Accessory\AccessoryLowercaseStringType;
+use PHPStan\Type\Accessory\AccessoryNonEmptyStringType;
+use PHPStan\Type\Accessory\AccessoryNonFalsyStringType;
+use PHPStan\Type\Accessory\AccessoryUppercaseStringType;
+use PHPStan\Type\Constant\ConstantStringType;
+use PHPStan\Type\DynamicFunctionReturnTypeExtension;
+use PHPStan\Type\IntersectionType;
+use PHPStan\Type\StringType;
+use PHPStan\Type\Type;
+use PHPStan\Type\TypeCombinator;
+use function count;
+use function strrev;
+
+final class StrrevFunctionReturnTypeExtension implements DynamicFunctionReturnTypeExtension
+{
+
+	public function isFunctionSupported(FunctionReflection $functionReflection): bool
+	{
+		return $functionReflection->getName() === 'strrev';
+	}
+
+	public function getTypeFromFunctionCall(
+		FunctionReflection $functionReflection,
+		FuncCall $functionCall,
+		Scope $scope,
+	): Type
+	{
+		$args = $functionCall->getArgs();
+		if (count($args) < 1) {
+			return new StringType();
+		}
+
+		$inputType = $scope->getType($args[0]->value);
+		$constantStrings = $inputType->getConstantStrings();
+		if (count($constantStrings) > 0) {
+			$resultTypes = [];
+			foreach ($constantStrings as $constantString) {
+				$resultTypes[] = new ConstantStringType(strrev($constantString->getValue()));
+			}
+
+			return TypeCombinator::union(...$resultTypes);
+		}
+
+		$accessoryTypes = [];
+		if ($inputType->isNonFalsyString()->yes()) {
+			$accessoryTypes[] = new AccessoryNonFalsyStringType();
+		} elseif ($inputType->isNonEmptyString()->yes()) {
+			$accessoryTypes[] = new AccessoryNonEmptyStringType();
+		}
+		if ($inputType->isLowercaseString()->yes()) {
+			$accessoryTypes[] = new AccessoryLowercaseStringType();
+		}
+		if ($inputType->isUppercaseString()->yes()) {
+			$accessoryTypes[] = new AccessoryUppercaseStringType();
+		}
+
+		if (count($accessoryTypes) > 0) {
+			$accessoryTypes[] = new StringType();
+
+			return new IntersectionType($accessoryTypes);
+		}
+
+		return new StringType();
+	}
+
+}

tests/PHPStan/Analyser/nsrt/strrev.php

@@ -0,0 +1,37 @@
+<?php
+
+namespace Strrev;
+
+use function PHPStan\Testing\assertType;
+
+class Foo
+{
+	/**
+	 * @param string $string
+	 * @param non-empty-string $nonEmptyString
+	 * @param non-falsy-string $nonFalsyString
+	 * @param numeric-string $numericString
+	 * @param lowercase-string $lowercaseString
+	 * @param uppercase-string $uppercaseString
+	 * @param 'foo'|'bar' $constantStrings
+	 *
+	 * @return void
+	 */
+	public function test(
+		string $string,
+		string $nonEmptyString,
+		string $nonFalsyString,
+		string $numericString,
+		string $lowercaseString,
+		string $uppercaseString,
+		string $constantStrings,
+	) {
+		assertType('string', strrev($string));
+		assertType('non-empty-string', strrev($nonEmptyString));
+		assertType('non-falsy-string', strrev($nonFalsyString));
+		assertType('non-empty-string', strrev($numericString));
+		assertType('lowercase-string', strrev($lowercaseString));
+		assertType('uppercase-string', strrev($uppercaseString));
+		assertType("'oof'|'rab'", strrev($constantStrings));
+	}
+}