The expression a <=> b returns an object that compares <0 if a < b, compares >0 if a > b, and compares ==0 if a and b are equal/equivalent.
The expression blah-blah returns an object that compares less than zero if blah-blah...
Does this sentence make sense in English? Is this grammatically correct? Is this some grammar variant used by programmers? Can you change the verb "to compare" in the quoted text with something else while preserving the original meaning?