when it cannot match a prototype eg:

module foo;
enum Foo
{
foo
}
void bar(Foo foo)
{
}
module bar;
enum Foo
{
foo
}

void fooBar(Foo foo)
{
  bar(foo);
}

rather than complain the type X does not match the type X - an unhelpful message - could the compiler not check to see if the type descriptions are identical, and if so print a clarifying message about which modules they come from.  it's easy the second time, but another source of friction in learning the language in the beginning.