Type Alias GzipReader 

pub type GzipReader<R> = MultiGzDecoder<R>;

MultiGzDecoder, never GzDecoder: concatenated members are what a gzip file is here — BGZF is nothing else, and bgzip writes one member per block — and only the multi variant walks past the first.

Aliased Type

pub struct GzipReader<R> { /* private fields */ }