diff --git a/composer.json b/composer.json
index 66160e1..5160d18 100644
--- a/composer.json
+++ b/composer.json
@@ -12,7 +12,8 @@
   ],
   "require": {
     "php": "^8.0",
-    "ext-mbstring": "*"
+    "ext-mbstring": "^8.0",
+    "psr/log": "^2.0 || ^3.0"
   },
   "require-dev": {
     "ergebnis/composer-normalize": "^2.15",
diff --git a/composer.lock b/composer.lock
index 69e923e..ec737fb 100644
--- a/composer.lock
+++ b/composer.lock
@@ -4,8 +4,59 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
         "This file is @generated automatically"
     ],
-    "content-hash": "c9bd0e80e7e22f425eb286b5c42b5f54",
-    "packages": [],
+    "content-hash": "6d73951acc3119aabd404dbbe0967053",
+    "packages": [
+        {
+            "name": "psr/log",
+            "version": "3.0.0",
+            "source": {
+                "type": "git",
+                "url": "https://github.com/php-fig/log.git",
+                "reference": "fe5ea303b0887d5caefd3d431c3e61ad47037001"
+            },
+            "dist": {
+                "type": "zip",
+                "url": "https://api.github.com/repos/php-fig/log/zipball/fe5ea303b0887d5caefd3d431c3e61ad47037001",
+                "reference": "fe5ea303b0887d5caefd3d431c3e61ad47037001",
+                "shasum": ""
+            },
+            "require": {
+                "php": ">=8.0.0"
+            },
+            "type": "library",
+            "extra": {
+                "branch-alias": {
+                    "dev-master": "3.x-dev"
+                }
+            },
+            "autoload": {
+                "psr-4": {
+                    "Psr\\Log\\": "src"
+                }
+            },
+            "notification-url": "https://packagist.org/downloads/",
+            "license": [
+                "MIT"
+            ],
+            "authors": [
+                {
+                    "name": "PHP-FIG",
+                    "homepage": "https://www.php-fig.org/"
+                }
+            ],
+            "description": "Common interface for logging libraries",
+            "homepage": "https://github.com/php-fig/log",
+            "keywords": [
+                "log",
+                "psr",
+                "psr-3"
+            ],
+            "support": {
+                "source": "https://github.com/php-fig/log/tree/3.0.0"
+            },
+            "time": "2021-07-14T16:46:02+00:00"
+        }
+    ],
     "packages-dev": [
         {
             "name": "dealerdirect/phpcodesniffer-composer-installer",
@@ -526,16 +577,16 @@
         },
         {
             "name": "phpstan/phpdoc-parser",
-            "version": "1.13.0",
+            "version": "1.13.1",
             "source": {
                 "type": "git",
                 "url": "https://github.com/phpstan/phpdoc-parser.git",
-                "reference": "33aefcdab42900e36366d0feab6206e2dd68f947"
+                "reference": "aac44118344d197e6d5f7c6cee91885f0a89acdd"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/phpstan/phpdoc-parser/zipball/33aefcdab42900e36366d0feab6206e2dd68f947",
-                "reference": "33aefcdab42900e36366d0feab6206e2dd68f947",
+                "url": "https://api.github.com/repos/phpstan/phpdoc-parser/zipball/aac44118344d197e6d5f7c6cee91885f0a89acdd",
+                "reference": "aac44118344d197e6d5f7c6cee91885f0a89acdd",
                 "shasum": ""
             },
             "require": {
@@ -565,22 +616,22 @@
             "description": "PHPDoc parser with support for nullable, intersection and generic types",
             "support": {
                 "issues": "https://github.com/phpstan/phpdoc-parser/issues",
-                "source": "https://github.com/phpstan/phpdoc-parser/tree/1.13.0"
+                "source": "https://github.com/phpstan/phpdoc-parser/tree/1.13.1"
             },
-            "time": "2022-10-21T09:57:39+00:00"
+            "time": "2022-11-20T08:52:26+00:00"
         },
         {
             "name": "phpstan/phpstan",
-            "version": "1.8.11",
+            "version": "1.9.2",
             "source": {
                 "type": "git",
                 "url": "https://github.com/phpstan/phpstan.git",
-                "reference": "46e223dd68a620da18855c23046ddb00940b4014"
+                "reference": "d6fdf01c53978b6429f1393ba4afeca39cc68afa"
             },
             "dist": {
                 "type": "zip",
-                "url": "https://api.github.com/repos/phpstan/phpstan/zipball/46e223dd68a620da18855c23046ddb00940b4014",
-                "reference": "46e223dd68a620da18855c23046ddb00940b4014",
+                "url": "https://api.github.com/repos/phpstan/phpstan/zipball/d6fdf01c53978b6429f1393ba4afeca39cc68afa",
+                "reference": "d6fdf01c53978b6429f1393ba4afeca39cc68afa",
                 "shasum": ""
             },
             "require": {
@@ -610,7 +661,7 @@
             ],
             "support": {
                 "issues": "https://github.com/phpstan/phpstan/issues",
-                "source": "https://github.com/phpstan/phpstan/tree/1.8.11"
+                "source": "https://github.com/phpstan/phpstan/tree/1.9.2"
             },
             "funding": [
                 {
@@ -626,7 +677,7 @@
                     "type": "tidelift"
                 }
             ],
-            "time": "2022-10-24T15:45:13+00:00"
+            "time": "2022-11-10T09:56:11+00:00"
         },
         {
             "name": "phpstan/phpstan-deprecation-rules",
@@ -851,7 +902,7 @@
     "prefer-lowest": false,
     "platform": {
         "php": "^8.0",
-        "ext-mbstring": "*"
+        "ext-mbstring": "^8.0"
     },
     "platform-dev": [],
     "plugin-api-version": "2.3.0"
diff --git a/phpcs.xml.dist b/phpcs.xml.dist
index bf40ce2..fe0b85e 100644
--- a/phpcs.xml.dist
+++ b/phpcs.xml.dist
@@ -636,6 +636,10 @@
         <severity>5</severity>
     </rule>
 
+    <rule ref="SlevomatCodingStandard.TypeHints.ParameterTypeHint.MissingNativeTypeHint">
+        <exclude-pattern>src/StdoutMessageLogger.php</exclude-pattern>
+    </rule>
+
     <rule ref="SlevomatCodingStandard.Classes.SuperfluousAbstractClassNaming.SuperfluousPrefix">
         <exclude-pattern>src/Atn/Transitions/AbstractPredicateTransition.php</exclude-pattern>
     </rule>
diff --git a/src/Atn/ATNConfig.php b/src/Atn/ATNConfig.php
index 425b9b0..7e9c9b9 100644
--- a/src/Atn/ATNConfig.php
+++ b/src/Atn/ATNConfig.php
@@ -157,7 +157,7 @@ public function toString(bool $showAlt): string
             $buf .= ',[' . $this->context . ']';
         }
 
-        if ($this->semanticContext->equals(SemanticContext::none())) {
+        if (!$this->semanticContext->equals(SemanticContext::none())) {
             $buf .= ',' . $this->semanticContext;
         }
 
@@ -177,9 +177,9 @@ public function __toString(): string
             $this->state,
             $this->alt,
             $this->context !== null ? ',[' . $this->context . ']' : '',
-            $this->semanticContext->equals(SemanticContext::none()) ?
-                ',' . $this->semanticContext :
-                '',
+            $this->semanticContext->equals(SemanticContext::none())
+                ? ''
+                : ',' . $this->semanticContext,
             $this->reachesIntoOuterContext > 0 ? ',up=' . $this->reachesIntoOuterContext : '',
         );
     }
diff --git a/src/Atn/ParserATNSimulator.php b/src/Atn/ParserATNSimulator.php
index 36c31a4..57fb55a 100644
--- a/src/Atn/ParserATNSimulator.php
+++ b/src/Atn/ParserATNSimulator.php
@@ -24,6 +24,7 @@
 use Antlr\Antlr4\Runtime\Error\Exceptions\RecognitionException;
 use Antlr\Antlr4\Runtime\IntervalSet;
 use Antlr\Antlr4\Runtime\IntStream;
+use Antlr\Antlr4\Runtime\LoggerProvider;
 use Antlr\Antlr4\Runtime\Parser;
 use Antlr\Antlr4\Runtime\ParserRuleContext;
 use Antlr\Antlr4\Runtime\PredictionContexts\PredictionContext;
@@ -35,6 +36,7 @@
 use Antlr\Antlr4\Runtime\Utils\BitSet;
 use Antlr\Antlr4\Runtime\Utils\DoubleKeyMap;
 use Antlr\Antlr4\Runtime\Utils\Set;
+use Psr\Log\LoggerInterface as Logger;
 
 /**
  * The embodiment of the adaptive LL(*), ALL(*), parsing strategy.
@@ -231,6 +233,8 @@
  */
 final class ParserATNSimulator extends ATNSimulator
 {
+    public static bool $traceAtnSimulation = false;
+
     protected Parser $parser;
 
     /** @var array<DFA> */
@@ -260,6 +264,8 @@ final class ParserATNSimulator extends ATNSimulator
 
     protected ?DFA $dfa = null;
 
+    private Logger $logger;
+
     /**
      * @param array<DFA> $decisionToDFA
      */
@@ -273,6 +279,7 @@ public function __construct(
 
         $this->parser = $parser;
         $this->decisionToDFA = $decisionToDFA;
+        $this->logger = LoggerProvider::getLogger();
     }
 
     public function reset(): void
@@ -296,6 +303,18 @@ public function clearDFA(): void
      */
     public function adaptivePredict(TokenStream $input, int $decision, ParserRuleContext $outerContext): int
     {
+        if (self::$traceAtnSimulation) {
+            $this->logger->debug(
+                'adaptivePredict decision {decision} exec LA(1)=={token} line {line}:{pos}',
+                [
+                    'decision' => $decision,
+                    'token' => $this->getTokenName($input->LA(1)),
+                    'line' => $input->LT(1)?->getLine(),
+                    'pos' => $input->LT(1)?->getCharPositionInLine(),
+                ],
+            );
+        }
+
         $this->input = $input;
         $this->startIndex = $input->getIndex();
         $this->outerContext = $outerContext;
@@ -404,6 +423,19 @@ public function execATN(
         int $startIndex,
         ParserRuleContext $outerContext,
     ): ?int {
+        if (self::$traceAtnSimulation) {
+            $this->logger->debug(
+                'execATN decision {decision}, DFA state {state}, LA(1)=={token} line {line}:{pos}',
+                [
+                    'decision' => $dfa->decision,
+                    'state' => $s0->__toString(),
+                    'token' => $this->getTokenName($input->LA(1)),
+                    'line' => $input->LT(1)?->getLine(),
+                    'pos' => $input->LT(1)?->getCharPositionInLine(),
+                ],
+            );
+        }
+
         $previousD = $s0;
 
         $t = $input->LA(1);
@@ -655,6 +687,12 @@ protected function execATNWithFullContext(
         int $startIndex,
         ParserRuleContext $outerContext,
     ): int {
+        if (self::$traceAtnSimulation) {
+            $this->logger->debug('execATNWithFullContext {state}', [
+                'state' => $s0->__toString(),
+            ]);
+        }
+
         $fullCtx = true;
         $foundExactAmbig = false;
         $reach = null;
@@ -890,15 +928,18 @@ protected function computeReachSet(ATNConfigSet $closure, int $t, bool $fullCtx)
          * multiple alternatives are viable.*/
 
         if ($skippedStopStates !== null && (!$fullCtx || !PredictionMode::hasConfigInRuleStopState($reach))) {
-            if (\count($skippedStopStates) === 0) {
-                throw new \LogicException('Skipped stop states cannot be empty.');
-            }
-
             foreach ($skippedStopStates as $lValue) {
                 $reach->add($lValue, $this->mergeCache);
             }
         }
 
+        if (self::$traceAtnSimulation) {
+            $this->logger->debug('computeReachSet {closure} -> {reach}', [
+                'closure' => $closure->__toString(),
+                'reach' => $reach->__toString(),
+            ]);
+        }
+
         if ($reach->isEmpty()) {
             return null;
         }
@@ -964,6 +1005,13 @@ protected function computeStartState(ATNState $p, RuleContext $ctx, bool $fullCt
         $initialContext = PredictionContext::fromRuleContext($this->atn, $ctx);
         $configs = new ATNConfigSet($fullCtx);
 
+        if (self::$traceAtnSimulation) {
+            $this->logger->debug('computeStartState from ATN state {state} initialContext={initialContext}', [
+                'state' => $p->__toString(),
+                'initialContext' => $initialContext->__toString(),
+            ]);
+        }
+
         foreach ($p->getTransitions() as $i => $t) {
             $c = new ATNConfig(null, $t->target, $initialContext, null, $i + 1);
             $closureBusy = new Set();
@@ -1464,6 +1512,12 @@ protected function closureCheckingStopState(
         int $depth,
         bool $treatEofAsEpsilon,
     ): void {
+        if (self::$traceAtnSimulation) {
+            $this->logger->debug('closure({config})', [
+                'config' => $config->toString(true),
+            ]);
+        }
+
         if ($config->state instanceof RuleStopState) {
             // We hit rule end. If we have context info, use it run thru all possible stack tops in ctx
             $context = $config->context;
@@ -2150,6 +2204,12 @@ protected function addDFAState(DFA $dfa, DFAState $D): DFAState
         $existing = $dfa->states->get($D);
 
         if ($existing instanceof DFAState) {
+            if (self::$traceAtnSimulation) {
+                $this->logger->debug('addDFAState {state} exists', [
+                    'state' => $D->__toString(),
+                ]);
+            }
+
             return $existing;
         }
 
@@ -2160,6 +2220,12 @@ protected function addDFAState(DFA $dfa, DFAState $D): DFAState
             $D->configs->setReadonly(true);
         }
 
+        if (self::$traceAtnSimulation) {
+            $this->logger->debug('addDFAState new {state}', [
+                'state' => $D->__toString(),
+            ]);
+        }
+
         $dfa->states->add($D);
 
         return $D;
diff --git a/src/LoggerProvider.php b/src/LoggerProvider.php
new file mode 100644
index 0000000..5bb5cd1
--- /dev/null
+++ b/src/LoggerProvider.php
@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Antlr\Antlr4\Runtime;
+
+use Psr\Log\LoggerInterface as PsrLogger;
+
+final class LoggerProvider
+{
+    private static ?PsrLogger $logger = null;
+
+    public static function setLogger(PsrLogger $logger): void
+    {
+        self::$logger = $logger;
+    }
+
+    public static function getLogger(): PsrLogger
+    {
+        if (self::$logger === null) {
+            self::$logger = new StdoutMessageLogger();
+        }
+
+        return self::$logger;
+    }
+}
diff --git a/src/PredictionContexts/PredictionContext.php b/src/PredictionContexts/PredictionContext.php
index 8638b05..5e2c97c 100644
--- a/src/PredictionContexts/PredictionContext.php
+++ b/src/PredictionContexts/PredictionContext.php
@@ -5,8 +5,10 @@
 namespace Antlr\Antlr4\Runtime\PredictionContexts;
 
 use Antlr\Antlr4\Runtime\Atn\ATN;
+use Antlr\Antlr4\Runtime\Atn\ParserATNSimulator;
 use Antlr\Antlr4\Runtime\Atn\Transitions\RuleTransition;
 use Antlr\Antlr4\Runtime\Comparison\Hashable;
+use Antlr\Antlr4\Runtime\LoggerProvider;
 use Antlr\Antlr4\Runtime\RuleContext;
 use Antlr\Antlr4\Runtime\Utils\DoubleKeyMap;
 
@@ -392,12 +394,28 @@ public static function mergeArrays(
             $previous = $mergeCache->getByTwoKeys($a, $b);
 
             if ($previous !== null) {
+                if (ParserATNSimulator::$traceAtnSimulation) {
+                    LoggerProvider::getLogger()
+                        ->debug('mergeArrays a={a},b={b} -> previous', [
+                            'a' => $a->__toString(),
+                            'b' => $b->__toString(),
+                        ]);
+                }
+
                 return $previous;
             }
 
             $previous = $mergeCache->getByTwoKeys($b, $a);
 
             if ($previous !== null) {
+                if (ParserATNSimulator::$traceAtnSimulation) {
+                    LoggerProvider::getLogger()
+                        ->debug('mergeArrays a={a},b={b} -> previous', [
+                            'a' => $a->__toString(),
+                            'b' => $b->__toString(),
+                        ]);
+                }
+
                 return $previous;
             }
         }
@@ -500,6 +518,14 @@ public static function mergeArrays(
                 $mergeCache->set($a, $b, $a);
             }
 
+            if (ParserATNSimulator::$traceAtnSimulation) {
+                LoggerProvider::getLogger()
+                    ->debug('mergeArrays a={a},b={b} -> a', [
+                        'a' => $a->__toString(),
+                        'b' => $b->__toString(),
+                    ]);
+            }
+
             return $a;
         }
 
@@ -508,6 +534,14 @@ public static function mergeArrays(
                 $mergeCache->set($a, $b, $b);
             }
 
+            if (ParserATNSimulator::$traceAtnSimulation) {
+                LoggerProvider::getLogger()
+                    ->debug('mergeArrays a={a},b={b} -> b', [
+                        'a' => $a->__toString(),
+                        'b' => $b->__toString(),
+                    ]);
+            }
+
             return $b;
         }
 
@@ -515,6 +549,15 @@ public static function mergeArrays(
             $mergeCache->set($a, $b, $M);
         }
 
+        if (ParserATNSimulator::$traceAtnSimulation) {
+            LoggerProvider::getLogger()
+                ->debug('mergeArrays a={a},b={b} -> M', [
+                    'a' => $a->__toString(),
+                    'b' => $b->__toString(),
+                    'M' => $M->__toString(),
+                ]);
+        }
+
         return $M;
     }
 
diff --git a/src/StdoutMessageLogger.php b/src/StdoutMessageLogger.php
new file mode 100644
index 0000000..58d2af4
--- /dev/null
+++ b/src/StdoutMessageLogger.php
@@ -0,0 +1,33 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Antlr\Antlr4\Runtime;
+
+use Psr\Log\AbstractLogger;
+use Psr\Log\LoggerInterface as Logger;
+
+final class StdoutMessageLogger extends AbstractLogger implements Logger
+{
+    /**
+     * @param mixed        $level
+     * @param array<mixed> $context
+     */
+    public function log($level, \Stringable|string $message, array $context = []): void
+    {
+        \fwrite(\STDOUT, self::formatMessage($message, $context) . \PHP_EOL);
+    }
+
+    /**
+     * @param array<string, mixed> $context
+     */
+    private static function formatMessage(\Stringable|string $message, array $context): string
+    {
+        $replace = [];
+        foreach ($context as $key => $val) {
+            $replace['{' . $key . '}'] = $val;
+        }
+
+        return \strtr((string) $message, $replace);
+    }
+}
diff --git a/src/Utils/Pair.php b/src/Utils/Pair.php
index fc80417..3a3c5a3 100644
--- a/src/Utils/Pair.php
+++ b/src/Utils/Pair.php
@@ -38,6 +38,14 @@ public function hashCode(): int
 
     public function __toString(): string
     {
-        return \sprintf('%s, %s', (string) $this->a, (string) $this->b);
+        return \sprintf(
+            '%s, %s',
+            $this->a === null
+                ? 'null'
+                : ($this->a instanceof \Stringable ? (string) $this->a : $this->a::class),
+            $this->b === null
+                ? 'null'
+                : ($this->b instanceof \Stringable ? (string) $this->b : $this->b::class),
+        );
     }
 }