Function preprocessor_conditional_family_range 

pub fn preprocessor_conditional_family_range(
    root: Node<'_>,
    start_byte: usize,
    end_byte: usize,
) -> Option<(usize, usize)>

The byte range of the #if/#elif/#else chain that encloses the smallest node covering [start_byte, end_byte), or None when nothing there is conditional.

Two declarations of one name that report the same chain stand in different branches of it, so at most one of them is compiled in any configuration. They are alternate spellings of a single declaration, not competing declarations, and navigation must not present them as an ambiguity.