Improve definition handling for guessed receiver types (#2472)

It's not uncommon for Ruby programmers to name variables after a class's
superclass. But with guessed receiver types, such usages would actually
reduce the number of definitions returned.

For example, given the following code:

```rb
class Animal
end

class Cat < Animal
  def meow
    "Meow"
  end
end

animal = Cat.new
animal.meow # meow can't be found with experimented features enabled
```

This commit improves the definition handling for guessed receiver types
by treating them as unknown when no methods are found.

Author: st0012

lib/ruby_lsp/listeners/definition.rb

@@ -208,10 +208,13 @@ def handle_instance_variable_definition(name)
       def handle_method_definition(message, receiver_type, inherited_only: false)
         methods = if receiver_type
           @index.resolve_method(message, receiver_type.name, inherited_only: inherited_only)
-        else
-          # If the method doesn't have a receiver, then we provide a few candidates to jump to
-          # But we don't want to provide too many candidates, as it can be overwhelming
-          @index[message]&.take(MAX_NUMBER_OF_DEFINITION_CANDIDATES_WITHOUT_RECEIVER)
+        end
+
+        # If the method doesn't have a receiver, or the guessed receiver doesn't have any matched candidates,
+        # then we provide a few candidates to jump to
+        # But we don't want to provide too many candidates, as it can be overwhelming
+        if receiver_type.nil? || (receiver_type.is_a?(TypeInferrer::GuessedType) && methods.nil?)
+          methods = @index[message]&.take(MAX_NUMBER_OF_DEFINITION_CANDIDATES_WITHOUT_RECEIVER)
         end
 
         return unless methods

test/requests/definition_expectations_test.rb

@@ -472,6 +472,71 @@ def foo; end
     end
   end
 
+  def test_definition_for_guessed_receiver_is_listed
+    source = <<~RUBY
+      # typed: false
+
+      class Cheetah
+        def meow; end
+      end
+
+      class Cat
+        def meow; end
+      end
+
+      cat = Cat.new
+      cat.meow
+    RUBY
+
+    with_server(source) do |server, uri|
+      server.process_message(
+        id: 1,
+        method: "textDocument/definition",
+        params: { textDocument: { uri: uri }, position: { character: 4, line: 11 } },
+      )
+      response = server.pop_response.response
+
+      # Only Cat#meow is listed
+      assert_equal(1, response.size)
+      assert_equal(7, response.first.target_range.start.line)
+      assert_equal(7, response.first.target_range.end.line)
+      assert_equal(2, response.first.target_range.start.character)
+      assert_equal(15, response.first.target_range.end.character)
+    end
+  end
+
+  def test_guessed_receiver_is_treated_as_unknown_when_no_declaration_exists
+    source = <<~RUBY
+      # typed: false
+
+      class Animal
+        def eat; end
+      end
+
+      class Cheetah
+        def meow; end
+      end
+
+      class Cat
+        def meow; end
+      end
+
+      animal = Cat.new
+      animal.meow
+    RUBY
+
+    with_server(source) do |server, uri|
+      server.process_message(
+        id: 1,
+        method: "textDocument/definition",
+        params: { textDocument: { uri: uri }, position: { character: 7, line: 15 } },
+      )
+      response = server.pop_response.response
+
+      assert_equal(2, response.size)
+    end
+  end
+
   def test_definitions_for_unknown_receiver_is_capped
     source = +"# typed: false\n"