Deriving bug fixes #8285
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Deriving bug fixes #8285
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Previously it would call:
f(sf1.cmp(&of1), f(sf2.cmp(&of2), ...))
(where s/of1 = 'self/other field 1', and f was
std::cmp::lexical_ordering)
This meant that every .cmp subcall got evaluated when calling a derived
TotalOrd.cmp.
This corrects this to use
let test = sf1.cmp(&of1);
if test == Equal {
let test = sf2.cmp(&of2);
if test == Equal {
// ...
} else {
test
}
} else {
test
}
This gives a lexical ordering by short-circuiting on the first comparison
that is not Equal.
Closed
|
Could you add the tests into this PR as well (the ones that asserted short circuiting) Other than that, r=me |
|
Done. |
bors
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Aug 7, 2013
Some general clean-up relating to deriving: - `TotalOrd` was too eager, and evaluated the `.cmp` call for every field, even if it could short-circuit earlier. - the pointer types didn't have impls for `TotalOrd` or `TotalEq`. - the Makefiles didn't reach deep enough into libsyntax for dependencies. (Split out from #8258.)
flip1995
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to flip1995/rust
that referenced
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Jan 17, 2022
…5, r=Manishearth Erase late bound regions in `iter_not_returning_iterator` fixes rust-lang#8285 changelog: None
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Some general clean-up relating to deriving:
TotalOrdwas too eager, and evaluated the.cmpcall for every field, even if it could short-circuit earlier.TotalOrdorTotalEq.(Split out from #8258.)