Cache calls to ClassReflection::isSubclassOf()

Author: lookyman

src/Reflection/ClassReflection.php

@@ -81,6 +81,9 @@ class ClassReflection implements ReflectionWithFilename
 /** @var string|null */
 private $cacheKey;
 
+/** @var array<string, bool> */
+private $subclasses = [];
+
 /**
  * @param \PHPStan\Reflection\ReflectionProvider $reflectionProvider
  * @param \PHPStan\Type\FileTypeMapper $fileTypeMapper
@@ -439,11 +442,15 @@ public function isAnonymous(): bool
 
 public function isSubclassOf(string $className): bool
 {
+if (isset($this->subclasses[$className])) {
+return $this->subclasses[$className];
+}
+
 if (!$this->reflectionProvider->hasClass($className)) {
-return false;
+return $this->subclasses[$className] = false;
 }
 
-return $this->reflection->isSubclassOf($className);
+return $this->subclasses[$className] = $this->reflection->isSubclassOf($className);
 }
 
 /**