Psalm - a static analysis tool for PHP

<?php

interface BasePackage {}

interface InnerPackage extends BasePackage {}

/**
 * @template TInnerPackage of InnerPackage
 */
interface GenericPackage extends BasePackage {
    /** @return TInnerPackage */
    public function unwrap() : InnerPackage;
}

interface SomeInnerPackage extends InnerPackage {}

/**
 * @extends GenericPackage<SomeInnerPackage>
 */
interface SomePackage extends GenericPackage {}

/**
 * @template TInnerPackage of InnerPackage
 * @template TGenericPackage of GenericPackage<TInnerPackage>
 * @param TGenericPackage $package
 * @return TInnerPackage
 */
function unwrapGeneric(GenericPackage $package) {
    return $package->unwrap();
}

/**
 * @template TInnerPackage of InnerPackage
 * @template TGenericPackage of GenericPackage<TInnerPackage>
 * @param  class-string<TGenericPackage> $class  FQCN to be instantiated
 * @return TInnerPackage
 */
function loadWithDirectUnwrap(string $class) {
    $package = new $class();
    return $package->unwrap();
}

/**
 * @template TInnerPackage of InnerPackage
 * @template TGenericPackage of GenericPackage<TInnerPackage>
 * @param  class-string<TGenericPackage> $class  FQCN to be instantiated
 * @return TInnerPackage
 */
function loadWithIndirectUnwrap(string $class) {
    $package = new $class();
    return unwrapGeneric($package);
}

$result = loadWithDirectUnwrap(SomePackage::class);
/** @psalm-trace $result */
// expected: SomePackage|SomeInnerPackage

Snippet created on February 26 2021 at 19:12 UTC