Extract isSuperTypeOf method on ExpressionTypeHolder

Addresses review feedback: extract the certainty + isSuperTypeOf check
into an ExpressionTypeHolder::isSuperTypeOf() method, mirroring the
existing equals() method pattern.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: phpstan-bot

src/Analyser/ExpressionTypeHolder.php

@@ -50,6 +50,19 @@ public function equals(self $other): bool
 		return $this->type === $other->type || $this->type->equals($other->type);
 	}
 
+	public function isSuperTypeOf(self $other): bool
+	{
+		if ($this === $other) {
+			return true;
+		}
+
+		if (!$this->certainty->equals($other->certainty)) {
+			return false;
+		}
+
+		return $this->type === $other->type || $this->type->isSuperTypeOf($other->type)->yes();
+	}
+
 	public function and(self $other): self
 	{
 		if ($this->type === $other->type || $this->type->equals($other->type)) {

src/Analyser/MutatingScope.php

@@ -3230,10 +3230,7 @@ public function filterBySpecifiedTypes(SpecifiedTypes $specifiedTypes): self
 						}
 						if (!$specifiedExpressions[$holderExprString]->equals($conditionalTypeHolder)) {
 							$allExact = false;
-							if (
-								!$specifiedExpressions[$holderExprString]->getCertainty()->equals($conditionalTypeHolder->getCertainty())
-								|| !$conditionalTypeHolder->getType()->isSuperTypeOf($specifiedExpressions[$holderExprString]->getType())->yes()
-							) {
+							if (!$conditionalTypeHolder->isSuperTypeOf($specifiedExpressions[$holderExprString])) {
 								$allSuperType = false;
 								break;
 							}