The language syntax here is a little nuts.
If you put an '=' after 'module test' then your original first errors will go away (entities must be indented). Then they become entities named e.g. 'Filename.test.x' - you are using the implicit module. Without the '=', you get rid of the implicit module, and the entire file goes in a module named 'test' (e.g. 'test.x'), and you don't indent (apparently indenting makes it a 'do' expression, which is incomplete if it only contains 'let's as there's no body).
I need to write a blog to explain all this in more detail. I'll also file a bug for better error diagnostics.