Rollup merge of #147101 - yotamofek:pr/iter-eq-and-eq-by, r=jdonszelmann

Use `Iterator::eq` and (dogfood) `eq_by` in compiler and library

Now that rust-lang/rust#137122 has landed, we can replace stuff that looks like:
```rust
let a: &[T];
let b: &[T];
let eq = a.len() == b.len() && a.iter().zip(b).all(|(a,b)| a == b)
```
with the much simpler `a.iter().eq(b)`, without losing the perf benefit of the different-length-fast-path.
Also dogfooded `Iterator::eq_by` (cc rust-lang/rust#64295 ) while I'm at it.

First commit (4d1b6fad230f8a5ccceccc7562eadc4ea50059da) should be very straightforward to review, second one (049a4606cb3906787aedf508ee8eea09c2bb3b9a) is slightly more creative, but IMHO a nice cleanup.

2 files changed, 2 insertions, 1 deletions

diff --git a/src/librustdoc/clean/types.rs b/src/librustdoc/clean/types.rs
index c2cf39c4be0..4eb32585ffb 100644
--- a/src/librustdoc/clean/types.rs
+++ b/src/librustdoc/clean/types.rs
@@ -1685,7 +1685,7 @@ impl Type {
         match (self_cleared, other_cleared) {
             // Recursive cases.
             (Type::Tuple(a), Type::Tuple(b)) => {
-                a.len() == b.len() && a.iter().zip(b).all(|(a, b)| a.is_doc_subtype_of(b, cache))
+                a.iter().eq_by(b, |a, b| a.is_doc_subtype_of(b, cache))
             }
             (Type::Slice(a), Type::Slice(b)) => a.is_doc_subtype_of(b, cache),
             (Type::Array(a, al), Type::Array(b, bl)) => al == bl && a.is_doc_subtype_of(b, cache),
diff --git a/src/librustdoc/lib.rs b/src/librustdoc/lib.rs
index c4f24e09ddb..d7ffb25f8bd 100644
--- a/src/librustdoc/lib.rs
+++ b/src/librustdoc/lib.rs
@@ -13,6 +13,7 @@
 #![feature(if_let_guard)]
 #![feature(iter_advance_by)]
 #![feature(iter_intersperse)]
+#![feature(iter_order_by)]
 #![feature(rustc_private)]
 #![feature(test)]
 #![warn(rustc::internal)]