Function rustc_mir::util::pretty::create_dump_file

pub(crate) fn create_dump_file<'tcx>(
    tcx: TyCtxt<'_>, 
    extension: &str, 
    pass_num: Option<&dyn Display>, 
    pass_name: &str, 
    disambiguator: &dyn Display, 
    source: MirSource<'tcx>
) -> Result<BufWriter<File>>

Attempts to open a file where we should dump a given MIR or other bit of MIR-related data. Used by mir-dump, but also by other bits of code (e.g., NLL inference) that dump graphviz data or other things, and hence takes the extension as an argument.