Fix stack StackLevelError during self referential constant resolution (#3799)

* Fix stack StackLevelError during self referential constant resolution

* Move test case and simplify it

Author: pkondzior

lib/ruby_indexer/lib/ruby_indexer/index.rb

@@ -907,6 +907,9 @@ def resolve_alias(entry, seen_names)
       target = resolve(entry.target, entry.nesting, seen_names)
       return entry unless target
 
+      # Self referential alias can be unresolved we should bail out from resolving
+      return entry if target.first == entry
+
       target_name = target.first #: as !nil
         .name
       resolved_alias = Entry::ConstantAlias.new(target_name, entry)

lib/ruby_indexer/test/index_test.rb

@@ -1175,6 +1175,23 @@ module D
       assert_equal("A::B::C", entry.target)
     end
 
+    def test_resolving_non_existing_self_referential_constant_alias
+      index(<<~RUBY)
+        module Foo
+          SomeClass = ::SomeClass
+          UNRESOLVED = SomeClass::CONSTANT
+        end
+      RUBY
+
+      entry = @index.resolve("Foo::UNRESOLVED", [])&.first #: as Entry::UnresolvedConstantAlias
+      assert_kind_of(Entry::UnresolvedConstantAlias, entry)
+      assert_equal(3, entry.location.start_line)
+      assert_equal("SomeClass::CONSTANT", entry.target)
+
+      entry = @index.resolve("SomeClass::CONSTANT", ["Foo"])
+      refute(entry)
+    end
+
     def test_resolving_qualified_references
       index(<<~RUBY)
         module Namespace