Function rustc_hir_pretty::print_crate

pub fn print_crate<'a>(
    sm: &'a SourceMap, 
    krate: &Crate<'_>, 
    filename: FileName, 
    input: String, 
    ann: &'a dyn PpAnn
) -> String

Requires you to pass an input filename and reader so that it can scan the input text for comments to copy forward.