Function apply_tile_defaults 

pub fn apply_tile_defaults(
    file: &mut PolydatFile,
    defaults: &TileOptions,
) -> Result<(), String>

Give every tile that declares no delimiters or sigil of its own the host’s defaults (SRD 114 §5.6, §10), re-reading its body under them.

A tile that names any option keeps all of them; the transform only fills in what the author left to the default. Tiles inside module bodies are rewritten too, since they compile in this program.