Skip compiling constants with alias from another gem in namespace

lib/tapioca/gem/pipeline.rb

@@ -391,6 +391,7 @@ def skip_constant?(name, constant)
       def skip_alias?(name, constant)
         return true if symbol_in_payload?(name)
         return true unless constant_in_gem?(name)
+        return true if has_aliased_namespace?(name)
 
         false
       end

lib/tapioca/runtime/reflection.rb

@@ -255,6 +255,23 @@ def child_module_for_parent_with_name(parent, name)
       def method_defined_by_forwardable_module?(method)
         method.source_location&.first == Object.const_source_location(:Forwardable)&.first
       end
+
+      sig { params(name: String).returns(T::Boolean) }
+      def has_aliased_namespace?(name)
+        name_parts = name.split("::")
+        name_parts.pop # drop the constant name, leaving just the namespace
+
+        name_parts.each_with_object([]) do |name_part, namespaces|
+          namespaces << "#{namespaces.last}::#{name_part}".delete_prefix("::")
+        end.any? do |namespace|
+          constant = constantize(namespace)
+          next unless Module === constant
+
+          # If the constant name doesn't match the namespace,
+          # the namespace must contain an alias
+          name_of(constant) != namespace
+        end
+      end
     end
   end
 end

spec/tapioca/cli/gem_spec.rb

@@ -1631,6 +1631,53 @@ def baz; end
           assert_empty_stderr(result)
           assert_success_status(result)
         end
+
+        it "does not generate RBI if namespace contains alias from different gem" do
+          foo = mock_gem("foo", "0.0.1") do
+            write!("lib/foo.rb", <<~RB)
+              module Foo; end
+              F = Foo
+            RB
+          end
+
+          bar = mock_gem("bar", "0.0.1") do
+            write!("lib/bar.rb", <<~RB)
+              module Foo
+                module Bar; end
+              end
+              F::B = Foo::Bar
+            RB
+          end
+
+          @project.require_mock_gem(foo, require: false)
+          @project.require_mock_gem(bar, require: false)
+
+          @project.bundle_install!
+          @project.tapioca("gem foo bar")
+
+          assert_project_file_equal("sorbet/rbi/gems/foo@0.0.1.rbi", <<~RBI)
+            # typed: true
+
+            # DO NOT EDIT MANUALLY
+            # This is an autogenerated file for types exported from the `foo` gem.
+            # Please instead update this file by running `bin/tapioca gem foo`.
+
+            F = Foo
+            module Foo; end
+          RBI
+
+          assert_project_file_equal("sorbet/rbi/gems/bar@0.0.1.rbi", <<~RBI)
+            # typed: true
+
+            # DO NOT EDIT MANUALLY
+            # This is an autogenerated file for types exported from the `bar` gem.
+            # Please instead update this file by running `bin/tapioca gem bar`.
+
+            module Foo; end
+            Foo::B = Foo::Bar
+            module Foo::Bar; end
+          RBI
+        end
       end
 
       describe "sync" do