Cache descriptions in ObjectType and UnionType

src/Type/ObjectType.php

@@ -87,6 +87,8 @@ class ObjectType implements TypeWithClassName, SubtractableType
 	/** @var array<string, self|null> */
 	private array $currentAncestors = [];
 
+	private ?string $cachedDescription = null;
+
 	/** @api */
 	public function __construct(
 		private string $className,
@@ -449,8 +451,12 @@ protected function describeAdditionalCacheKey(): string
 
 	private function describeCache(): string
 	{
+		if ($this->cachedDescription !== null) {
+			return $this->cachedDescription;
+		}
+
 		if (static::class !== self::class) {
-			return $this->describe(VerbosityLevel::cache());
+			return $this->cachedDescription = $this->describe(VerbosityLevel::cache());
 		}
 
 		$description = $this->className;
@@ -475,7 +481,7 @@ private function describeCache(): string
 			$description .= '-';
 		}
 
-		return $description;
+		return $this->cachedDescription = $description;
 	}
 
 	public function toNumber(): Type

src/Type/UnionType.php

@@ -38,6 +38,9 @@ class UnionType implements CompoundType
 
 	private bool $sortedTypes = false;
 
+	/** @var array<int, string> */
+	private array $cachedDescriptions = [];
+
 	/**
 	 * @api
 	 * @param Type[] $types
@@ -208,6 +211,9 @@ public function equals(Type $type): bool
 
 	public function describe(VerbosityLevel $level): string
 	{
+		if (isset($this->cachedDescriptions[$level->getLevelValue()])) {
+			return $this->cachedDescriptions[$level->getLevelValue()];
+		}
 		$joinTypes = static function (array $types) use ($level): string {
 			$typeNames = [];
 			foreach ($types as $i => $type) {
@@ -240,7 +246,7 @@ public function describe(VerbosityLevel $level): string
 			return implode('|', $typeNames);
 		};
 
-		return $level->handle(
+		return $this->cachedDescriptions[$level->getLevelValue()] = $level->handle(
 			function () use ($joinTypes): string {
 				$types = TypeCombinator::union(...array_map(static function (Type $type): Type {
 					if (