Correctly retrieve hasSideEffects metadata for inherited methods

Author: zonuexe

src/Reflection/Php/PhpClassReflectionExtension.php

@@ -839,7 +839,17 @@ public function createUserlandMethodReflection(ClassReflection $fileDeclaringCla
 		}
 		$isInternal = $resolvedPhpDoc->isInternal();
 		$isFinal = $resolvedPhpDoc->isFinal();
-		$isPure = $resolvedPhpDoc->isPure();
+		$isPure = null;
+		foreach ($actualDeclaringClass->getAncestors() as $className => $ancestor) {
+			if ($this->signatureMapProvider->hasMethodMetadata($className, $methodReflection->getName())) {
+				$hasSideEffects = $this->signatureMapProvider->getMethodMetadata($className, $methodReflection->getName())['hasSideEffects'];
+				$isPure = !$hasSideEffects;
+
+				break;
+			}
+		}
+
+		$isPure ??= $resolvedPhpDoc->isPure();
 		$asserts = Assertions::createFromResolvedPhpDocBlock($resolvedPhpDoc);
 		$acceptsNamedArguments = $resolvedPhpDoc->acceptsNamedArguments();
 		$selfOutType = $resolvedPhpDoc->getSelfOutTag() !== null ? $resolvedPhpDoc->getSelfOutTag()->getType() : null;

src/Reflection/SignatureMap/Php8SignatureMapProvider.php

@@ -64,9 +64,6 @@ public function __construct(
 	public function hasMethodSignature(string $className, string $methodName): bool
 	{
 		$lowerClassName = strtolower($className);
-		if ($lowerClassName === 'backedenum') {
-			return false;
-		}
 		if (!array_key_exists($lowerClassName, $this->map->classes)) {
 			return $this->functionSignatureMapProvider->hasMethodSignature($className, $methodName);
 		}

tests/PHPStan/Rules/Pure/PureFunctionRuleTest.php

@@ -174,4 +174,10 @@ public function testBug12224(): void
 		]);
 	}
 
+	#[RequiresPhp('>= 8.1')]
+	public function testBug13201(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-13201.php'], []);
+	}
+
 }

tests/PHPStan/Rules/Pure/data/bug-13201.php

@@ -0,0 +1,19 @@
+<?php // lint >= 8.1
+
+namespace PHPStan\Rules\Pure\data\Bug13201;
+
+enum Foo: string
+{
+
+	case Bar     = 'bar';
+	case Unknown = 'unknown';
+
+}
+
+/**
+ * @pure
+ */
+function createWithFallback(string $type): Foo
+{
+	return Foo::tryFrom($type) ?? Foo::Unknown;
+}