Fixed #3647: incorrect codegen for dispatch with union and module

spec/compiler/codegen/module_spec.cr

@@ -596,4 +596,30 @@ describe "Code gen: module" do
       bar.as(Moo(Char)).moo
       )).to_i.should eq(10)
   end
+
+  it "codegend dispatch of union with module (#3647)" do
+    run(%(
+      module Moo
+      end
+
+      class Foo
+        include Moo
+      end
+
+      class Bar < Foo
+      end
+
+      def foo(x : Int32)
+        1
+      end
+
+      def foo(x)
+        234
+      end
+
+      m = Bar.new.as(Moo)
+      a = m || 1
+      foo(a)
+      )).to_i.should eq(234)
+  end
 end

src/compiler/crystal/codegen/types.cr

@@ -80,7 +80,7 @@ module Crystal
   class NonGenericModuleType
     def append_to_expand_union_types(types)
       if including_types = @including_types
-        including_types.each &.append_to_expand_union_types(types)
+        including_types.each &.virtual_type.append_to_expand_union_types(types)
       else
         types << self
       end
@@ -90,7 +90,7 @@ module Crystal
   class GenericModuleInstanceType
     def append_to_expand_union_types(types)
       if including_types = @including_types
-        including_types.each &.append_to_expand_union_types(types)
+        including_types.each &.virtual_type.append_to_expand_union_types(types)
       else
         types << self
       end