Improve ReflectionEnum->getCases() performance

src/Reflection/Adapter/ReflectionEnum.php

@@ -33,6 +33,9 @@
  */
 final class ReflectionEnum extends CoreReflectionEnum
 {
+    /** @var list<ReflectionEnumUnitCase>|list<ReflectionEnumBackedCase>|null */
+    private array|null $cases = null;
+
     public function __construct(private BetterReflectionEnum $betterReflectionEnum)
     {
         unset($this->name);
@@ -527,17 +530,26 @@
         return new ReflectionEnumUnitCase($case);
     }
 
-    /** @return list<ReflectionEnumUnitCase|ReflectionEnumBackedCase> */
+    /** @return list<ReflectionEnumUnitCase>|list<ReflectionEnumBackedCase> */
     public function getCases(): array
     {
-        /** @psalm-suppress ImpureFunctionCall */
-        return array_map(function (BetterReflectionEnumCase $case): ReflectionEnumUnitCase|ReflectionEnumBackedCase {
-            if ($this->betterReflectionEnum->isBacked()) {
-                return new ReflectionEnumBackedCase($case);
+        if ($this->cases !== null) {
+            return $this->cases;
+        }
+
+        $isBacked = $this->betterReflectionEnum->isBacked();
+        $cases    = $this->betterReflectionEnum->getCases();
+
+        $mappedCases = [];
+        foreach ($cases as $case) {
+            if ($isBacked) {
+                $mappedCases[] = new ReflectionEnumBackedCase($case);
+            } else {
+                $mappedCases[] = new ReflectionEnumUnitCase($case);
             }
+        }
 
-            return new ReflectionEnumUnitCase($case);
-        }, array_values($this->betterReflectionEnum->getCases()));
+        return $this->cases = $mappedCases;
     }
 
     public function isBacked(): bool