Fix psalm errors

Author: Kirill Nesmeyanov

src/TypeResolver.php

@@ -67,13 +67,14 @@ public function resolveWith(TypeStatement $type, array $replacements): TypeState
             $replacements[\strtolower($key)] = $replacement;
         }
 
+        /** @var array<non-empty-lowercase-string, Name> $replacements */
         return $this->resolve($type, function (Name $name) use ($replacements) {
             $first = \strtolower($name->getFirstPartAsString());
 
             if (isset($replacements[$first])) {
                 $prefix = $replacements[$first];
 
-                return $prefix?->mergeWith($name);
+                return $prefix->mergeWith($name);
             }
 
             return null;

src/TypeResolver/TypeResolverVisitor.php

@@ -35,7 +35,10 @@ private function containsName(Node $node): bool
     public function enter(Node $node): ?Command
     {
         if ($this->containsName($node)) {
-            /** @var object{name: Name} $node */
+            /**
+             * @var object{name: Name} $node
+             * @psalm-suppress MixedAssignment
+             */
             $mapped = ($this->transform)($node->name);
 
             if ($mapped instanceof Name) {