Auto merge of #49881 - varkor:partialord-opt, r=Manishearth

Fix derive(PartialOrd) and optimise final field operation

```rust
// Before (`lt` on 2-field struct)
self.f1 < other.f1 || (!(other.f1 < self.f1) &&
(self.f2 < other.f2 || (!(other.f2 < self.f2) &&
(false)
))
)

// After
self.f1 < other.f1 || (!(other.f1 < self.f1) &&
self.f2 < other.f2
)

// Before (`le` on 2-field struct)
self.f1 < other.f1 || (!(other.f1 < self.f1) &&
(self.f2 < other.f2 || (!(other.f2 < self.f2) &&
(true)
))
)

// After
self.f1 < other.f1 || (self.f1 == other.f1 &&
self.f2 <= other.f2
)
```

(The big diff is mainly because of a past faulty rustfmt application that I corrected 😒)

Fixes #49650 and fixes #49505.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/etc/generate-deriving-span-tests.py b/src/etc/generate-deriving-span-tests.py
index 5b106275ac9..edb9389c00c 100755
--- a/src/etc/generate-deriving-span-tests.py
+++ b/src/etc/generate-deriving-span-tests.py
@@ -122,7 +122,7 @@ traits = {
 
 for (trait, supers, errs) in [('Clone', [], 1),
                               ('PartialEq', [], 2),
-                              ('PartialOrd', ['PartialEq'], 3),
+                              ('PartialOrd', ['PartialEq'], 5),
                               ('Eq', ['PartialEq'], 1),
                               ('Ord', ['Eq', 'PartialOrd', 'PartialEq'], 1),
                               ('Debug', [], 1),