pub fn parse_type(sm: &SourceMap, file: FileId) -> (Option<Ty>, Vec<Diagnostic>)
Parse a file holding exactly one type ((idx[64][seq: 8], idx[64][seq: 8])), as written in the header of a .psk.d data file.
(idx[64][seq: 8], idx[64][seq: 8])
.psk.d