auto merge of #19378 : japaric/rust/no-as-slice, r=alexcrichton

Now that we have an overloaded comparison (`==`) operator, and that `Vec`/`String` deref to `[T]`/`str` on method calls, many `as_slice()`/`as_mut_slice()`/`to_string()` calls have become redundant. This patch removes them. These were the most common patterns:

- `assert_eq(test_output.as_slice(), "ground truth")` -> `assert_eq(test_output, "ground truth")`
- `assert_eq(test_output, "ground truth".to_string())` -> `assert_eq(test_output, "ground truth")`
- `vec.as_mut_slice().sort()` -> `vec.sort()`
- `vec.as_slice().slice(from, to)` -> `vec.slice(from_to)`

---

Note that e.g. `a_string.push_str(b_string.as_slice())` has been left untouched in this PR, since we first need to settle down whether we want to favor the `&*b_string` or the `b_string[]` notation.

This is rebased on top of #19167

cc @alexcrichton @aturon 

1 files changed, 3 insertions, 3 deletions

diff --git a/src/libcoretest/tuple.rs b/src/libcoretest/tuple.rs
index be71e42ae9a..c53d82de23c 100644
--- a/src/libcoretest/tuple.rs
+++ b/src/libcoretest/tuple.rs
@@ -84,9 +84,9 @@ fn test_tuple_cmp() {
 #[test]
 fn test_show() {
     let s = format!("{}", (1i,));
-    assert_eq!(s.as_slice(), "(1,)");
+    assert_eq!(s, "(1,)");
     let s = format!("{}", (1i, true));
-    assert_eq!(s.as_slice(), "(1, true)");
+    assert_eq!(s, "(1, true)");
     let s = format!("{}", (1i, "hi", true));
-    assert_eq!(s.as_slice(), "(1, hi, true)");
+    assert_eq!(s, "(1, hi, true)");
 }