Function parse_program_tree_in 

pub fn parse_program_tree_in(
    src: &str,
    pack: &Yakugo,
) -> Result<Vec<Spanned>, ParseError>

parse_program_in keeping every node’s source span.

The same relation parse_program_tree has to parse_program, and it exists for the same reason: a surface is a spelling, so a program written in one has positions exactly as real as an English-surface program’s. Without this door, pipeline::run_in_surface would have to lift a spanless tree back up and every type error in a yakugo program would report <synthetic> — a position the parser HAD and threw away one line earlier, which is the class Diagnostic::span’s own docs name.

parse_program_in is now its projection, so the two cannot drift.

Errors

As parse_program_in.