psalm/src/CodeInspector/EffectsAnalyser.php

<?php

namespace CodeInspector;

use PhpParser;

/**
 * A class for analysing a given method call's effects in relation to
 * $this/self and also looking at return types
 */
class EffectsAnalyser
{
    /**
     * Gets the return types from a list of statements
     *
     * @param  array<PhpParser\Node\Stmt>  $stmts
     * @return array<string>    a list of return types
     */
    public static function getReturnTypes(array $stmts)
    {
        $return_types = [];

        foreach ($stmts as $stmt)
        {
            if ($stmt instanceof PhpParser\Node\Stmt\Return_) {
                if ($stmt->returnType === 'mixed') {
                    //var_dump($stmt);
                }
                $return_types[] = $stmt->returnType;

                break;

            } elseif ($stmt instanceof PhpParser\Node\Stmt\If_) {
                $return_types = array_merge($return_types, self::getReturnTypes($stmt->stmts));

                foreach ($stmt->elseifs as $elseif) {
                    $return_types = array_merge($return_types, self::getReturnTypes($elseif->stmts));
                }

                if ($stmt->else) {
                    $return_types = array_merge($return_types, self::getReturnTypes($stmt->else->stmts));
                }

            } elseif ($stmt instanceof PhpParser\Node\Stmt\TryCatch) {
                $return_types = array_merge($return_types, self::getReturnTypes($stmt->stmts));

                foreach ($stmt->catches as $catch) {
                    $return_types = array_merge($return_types, self::getReturnTypes($catch->stmts));
                }

                if ($stmt->finallyStmts) {
                    $return_types = array_merge($return_types, self::getReturnTypes($stmt->finallyStmts));
                }

            } elseif ($stmt instanceof PhpParser\Node\Stmt\For_) {
                $return_types = array_merge($return_types, self::getReturnTypes($stmt->stmts));

            } elseif ($stmt instanceof PhpParser\Node\Stmt\Foreach_) {
                $return_types = array_merge($return_types, self::getReturnTypes($stmt->stmts));

            } elseif ($stmt instanceof PhpParser\Node\Stmt\While_) {
                $return_types = array_merge($return_types, self::getReturnTypes($stmt->stmts));

            } elseif ($stmt instanceof PhpParser\Node\Stmt\Do_) {
                $return_types = array_merge($return_types, self::getReturnTypes($stmt->stmts));

            } elseif ($stmt instanceof PhpParser\Node\Stmt\Switch_) {
                foreach ($stmt->cases as $case) {
                    $return_types = array_merge($return_types, self::getReturnTypes($case->stmts));
                }
            }
        }

        // expand any nested return types
        $return_types = explode('|', implode('|', $return_types));

        if ($return_types === ['']) {
            $return_types = [];
        }

        $return_types = array_flip($return_types);

        if (count($return_types) > 1 && isset($return_types['void'])) {
            unset($return_types['void']);
            $return_types['null'] = 1;
        }

        if (count($return_types) > 1 && isset($return_types['false']) && isset($return_types['bool'])) {
            unset($return_types['false']);
        }

        return array_keys($return_types);
    }
}