diff --git a/conf/config.neon b/conf/config.neon
index cb8c20ad481..6c71dae9225 100644
--- a/conf/config.neon
+++ b/conf/config.neon
@@ -125,6 +125,7 @@ parameters:
 	universalObjectCratesClasses:
 		- stdClass
 	stubFiles:
+		- ../stubs/Memcached.stub
 		- ../stubs/Redis.stub
 		- ../stubs/ReflectionAttribute.stub
 		- ../stubs/ReflectionClassConstant.stub
diff --git a/src/Reflection/Php/PhpClassReflectionExtension.php b/src/Reflection/Php/PhpClassReflectionExtension.php
index fccce2fa772..a31e70433e3 100644
--- a/src/Reflection/Php/PhpClassReflectionExtension.php
+++ b/src/Reflection/Php/PhpClassReflectionExtension.php
@@ -618,6 +618,12 @@ private function createMethod(
 			$acceptsNamedArguments = true;
 			$selfOutType = null;
 			$phpDocComment = null;
+
+			$isPure = null;
+			if ($this->signatureMapProvider->hasMethodMetadata($declaringClassName, $methodReflection->getName())) {
+				$isPure = !$this->signatureMapProvider->getMethodMetadata($declaringClassName, $methodReflection->getName())['hasSideEffects'];
+			}
+
 			$methodSignaturesResult = $this->signatureMapProvider->getMethodSignatures($declaringClassName, $methodReflection->getName(), $methodReflection);
 			foreach ($methodSignaturesResult as $signatureType => $methodSignatures) {
 				if ($methodSignatures === null) {
@@ -693,6 +699,7 @@ private function createMethod(
 
 						$asserts = Assertions::createFromResolvedPhpDocBlock($currentResolvedPhpDoc);
 						$acceptsNamedArguments = $currentResolvedPhpDoc->acceptsNamedArguments();
+						$isPure ??= $currentResolvedPhpDoc->isPure();
 
 						$selfOutTypeTag = $currentResolvedPhpDoc->getSelfOutTag();
 						if ($selfOutTypeTag !== null) {
@@ -727,11 +734,15 @@ private function createMethod(
 				}
 			}
 
-			if ($this->signatureMapProvider->hasMethodMetadata($declaringClassName, $methodReflection->getName())) {
-				$hasSideEffects = TrinaryLogic::createFromBoolean($this->signatureMapProvider->getMethodMetadata($declaringClassName, $methodReflection->getName())['hasSideEffects']);
-			} else {
-				$hasSideEffects = TrinaryLogic::createMaybe();
+			if ($isPure === null) {
+				$classResolvedPhpDoc = $declaringClass->getResolvedPhpDoc();
+				if ($classResolvedPhpDoc !== null && $classResolvedPhpDoc->areAllMethodsPure()) {
+					$isPure = true;
+				} elseif ($classResolvedPhpDoc !== null && $classResolvedPhpDoc->areAllMethodsImpure()) {
+					$isPure = false;
+				}
 			}
+
 			return new NativeMethodReflection(
 				$this->reflectionProviderProvider->getReflectionProvider(),
 				$declaringClass,
@@ -739,7 +750,7 @@ private function createMethod(
 				$currentResolvedPhpDoc ?? null,
 				$variantsByType['positional'],
 				$variantsByType['named'] ?? null,
-				$hasSideEffects,
+				$isPure !== null ? TrinaryLogic::createFromBoolean(!$isPure) : TrinaryLogic::createMaybe(),
 				$throwType,
 				$asserts,
 				$acceptsNamedArguments,
diff --git a/stubs/Memcached.stub b/stubs/Memcached.stub
new file mode 100644
index 00000000000..5933a5d6c2c
--- /dev/null
+++ b/stubs/Memcached.stub
@@ -0,0 +1,6 @@
+<?php
+
+/**
+ * @phpstan-all-methods-impure
+ */
+class Memcached {}
diff --git a/tests/PHPStan/Rules/Comparison/Bug14534Test.php b/tests/PHPStan/Rules/Comparison/Bug14534Test.php
new file mode 100644
index 00000000000..a759a867887
--- /dev/null
+++ b/tests/PHPStan/Rules/Comparison/Bug14534Test.php
@@ -0,0 +1,40 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Comparison;
+
+use PHPStan\Analyser\RicherScopeGetTypeHelper;
+use PHPStan\Rules\Rule;
+use PHPStan\Testing\RuleTestCase;
+use function array_merge;
+
+/**
+ * @extends RuleTestCase<StrictComparisonOfDifferentTypesRule>
+ */
+class Bug14534Test extends RuleTestCase
+{
+
+	protected function getRule(): Rule
+	{
+		return new StrictComparisonOfDifferentTypesRule(
+			self::getContainer()->getByType(RicherScopeGetTypeHelper::class),
+			new PossiblyImpureTipHelper(true),
+			true,
+			true,
+			true,
+		);
+	}
+
+	public function testRule(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-14534.php'], []);
+	}
+
+	public static function getAdditionalConfigFiles(): array
+	{
+		return array_merge(
+			parent::getAdditionalConfigFiles(),
+			[__DIR__ . '/bug-14534.neon'],
+		);
+	}
+
+}
diff --git a/tests/PHPStan/Rules/Comparison/StrictComparisonOfDifferentTypesRuleTest.php b/tests/PHPStan/Rules/Comparison/StrictComparisonOfDifferentTypesRuleTest.php
index 9a057cd5392..9c8e1f25fc9 100644
--- a/tests/PHPStan/Rules/Comparison/StrictComparisonOfDifferentTypesRuleTest.php
+++ b/tests/PHPStan/Rules/Comparison/StrictComparisonOfDifferentTypesRuleTest.php
@@ -1197,6 +1197,11 @@ public function testBug14446(): void
 		$this->analyse([__DIR__ . '/../../Analyser/data/bug-14446.php'], []);
 	}
 
+	public function testBug13444(): void
+	{
+		$this->analyse([__DIR__ . '/data/bug-13444.php'], []);
+	}
+
 	public function testBug14473(): void
 	{
 		$this->analyse([__DIR__ . '/data/bug-14519.php'], []);
diff --git a/tests/PHPStan/Rules/Comparison/bug-14534.neon b/tests/PHPStan/Rules/Comparison/bug-14534.neon
new file mode 100644
index 00000000000..06adf3f5db4
--- /dev/null
+++ b/tests/PHPStan/Rules/Comparison/bug-14534.neon
@@ -0,0 +1,3 @@
+parameters:
+	stubFiles:
+		- data/bug-14534.stub
diff --git a/tests/PHPStan/Rules/Comparison/data/bug-13444.php b/tests/PHPStan/Rules/Comparison/data/bug-13444.php
new file mode 100644
index 00000000000..487ce9ae19e
--- /dev/null
+++ b/tests/PHPStan/Rules/Comparison/data/bug-13444.php
@@ -0,0 +1,28 @@
+<?php declare(strict_types = 1);
+
+namespace Bug13444;
+
+function sayStoreCas(string $key): void
+{
+	$memcached = new \Memcached();
+
+	do {
+		$extendedReturn = $memcached->get($key, null, \Memcached::GET_EXTENDED);
+
+		if ($memcached->getResultCode() !== \Memcached::RES_SUCCESS) {
+			return;
+		}
+
+		if (!is_array($extendedReturn) || !isset($extendedReturn['value']) || !isset($extendedReturn['cas'])) {
+			return;
+		}
+
+		$data = $extendedReturn['value'];
+		$cas = $extendedReturn['cas'];
+		\assert(is_float($cas));
+
+		// Do some work on the data..
+		$memcached->cas($cas, $key, $data);
+
+	} while ($memcached->getResultCode() !== \Memcached::RES_SUCCESS);
+}
diff --git a/tests/PHPStan/Rules/Comparison/data/bug-14534.php b/tests/PHPStan/Rules/Comparison/data/bug-14534.php
new file mode 100644
index 00000000000..31a893db5ac
--- /dev/null
+++ b/tests/PHPStan/Rules/Comparison/data/bug-14534.php
@@ -0,0 +1,12 @@
+<?php
+
+namespace Bug14534;
+
+function test(\SplFileObject $spl): bool
+{
+	if ($spl->key() === 1) {
+		return $spl->key() === 1;
+	}
+
+	return false;
+}
diff --git a/tests/PHPStan/Rules/Comparison/data/bug-14534.stub b/tests/PHPStan/Rules/Comparison/data/bug-14534.stub
new file mode 100644
index 00000000000..d1f3eeb3cc9
--- /dev/null
+++ b/tests/PHPStan/Rules/Comparison/data/bug-14534.stub
@@ -0,0 +1,6 @@
+<?php
+
+/**
+ * @phpstan-all-methods-impure
+ */
+class SplFileObject {}