rollup merge of #19832: japaric/no-nocopy
rollup merge of #19832: japaric/no-nocopy

r? @aturon / @alexcrichton

arthurprs/rand,retep998/rand,waynenilsen/rand,shepmaster/rand,bluss/rand,bhickey/rand,achanda/rand,ebfull/rand,huonw/rand,GrahamDennis/rand