Function expand_test_case

pub(crate) fn expand_test_case(
    ecx: &mut ExtCtxt<'_>,
    attr_sp: Span,
    meta_item: &MetaItem,
    anno_item: Annotatable,
) -> Vec<Annotatable>

#test_case is used by custom test authors to mark tests When building for test, it needs to make the item public and gensym the name Otherwise, we’ll omit the item. This behavior means that any item annotated with #test_case is never addressable.

We mark item with an inert attribute “rustc_test_marker” which the test generation logic will pick up on.