Fix property access on never type returning ErrorType instead of NeverType

When $case is narrowed to an impossible intersection type (e.g.
UnitEnum & BackedEnum = never), property access like $case->value
returned ErrorType. Since ErrorType extends MixedType, this corrupted
type inference in ternary expressions: union(ErrorType, string) became
mixed instead of string, causing false "invalid array key type mixed"
errors.

Now PropertyFetchHandler returns NeverType for property access on
NeverType, so union(NeverType, string) correctly simplifies to string.

Also skip InvalidComparisonOperationRule when either operand is
NeverType, since comparisons in dead code shouldn't be reported.

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

Author: phpstan-bot

src/Analyser/ExprHandler/PropertyFetchHandler.php

@@ -20,6 +20,7 @@
 use PHPStan\Rules\Properties\PropertyReflectionFinder;
 use PHPStan\Type\ErrorType;
 use PHPStan\Type\MixedType;
+use PHPStan\Type\NeverType;
 use PHPStan\Type\Type;
 use PHPStan\Type\TypeCombinator;
 use function array_map;
@@ -91,6 +92,11 @@ public function processExpr(NodeScopeResolver $nodeScopeResolver, Stmt $stmt, Ex
 	public function resolveType(MutatingScope $scope, Expr $expr): Type
 	{
 		if ($expr->name instanceof Identifier) {
+			$fetchedOnType = $scope->getType($expr->var);
+			if ($fetchedOnType instanceof NeverType) {
+				return new NeverType();
+			}
+
 			if ($scope->nativeTypesPromoted) {
 				$propertyReflection = $this->propertyReflectionFinder->findPropertyReflectionFromNode($expr, $scope);
 				if ($propertyReflection === null) {
@@ -108,7 +114,7 @@ public function resolveType(MutatingScope $scope, Expr $expr): Type
 
 			$returnType = $this->propertyFetchType(
 				$scope,
-				$scope->getType($expr->var),
+				$fetchedOnType,
 				$expr->name->name,
 				$expr,
 			);

src/Rules/Operators/InvalidComparisonOperationRule.php

@@ -17,6 +17,7 @@
 use PHPStan\Type\FloatType;
 use PHPStan\Type\IntegerType;
 use PHPStan\Type\MixedType;
+use PHPStan\Type\NeverType;
 use PHPStan\Type\NullType;
 use PHPStan\Type\ObjectWithoutClassType;
 use PHPStan\Type\Type;
@@ -60,6 +61,13 @@ public function processNode(Node $node, Scope $scope): array
 			return [];
 		}
 
+		$leftType = $scope->getType($node->left);
+		$rightType = $scope->getType($node->right);
+
+		if ($leftType instanceof NeverType || $rightType instanceof NeverType) {
+			return [];
+		}
+
 		$isLeftNumberType = $this->isNumberType($scope, $node->left);
 		$isRightNumberType = $this->isNumberType($scope, $node->right);
 		if ($isLeftNumberType === $isRightNumberType) {
@@ -68,8 +76,8 @@ public function processNode(Node $node, Scope $scope): array
 
 		$result = $this->operatorTypeSpecifyingExtensionRegistryProvider->getRegistry()->callOperatorTypeSpecifyingExtensions(
 			$node,
-			$scope->getType($node->left),
-			$scope->getType($node->right),
+			$leftType,
+			$rightType,
 		);
 
 		if ($result !== null) {