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, 1 insertions, 1 deletions

diff --git a/src/libfmt_macros/lib.rs b/src/libfmt_macros/lib.rs
index 03b65b3f71c..d88551eb855 100644
--- a/src/libfmt_macros/lib.rs
+++ b/src/libfmt_macros/lib.rs
@@ -440,7 +440,7 @@ mod tests {
 
     fn same(fmt: &'static str, p: &[Piece<'static>]) {
         let mut parser = Parser::new(fmt);
-        assert!(p == parser.collect::<Vec<Piece<'static>>>().as_slice());
+        assert!(p == parser.collect::<Vec<Piece<'static>>>());
     }
 
     fn fmtdflt() -> FormatSpec<'static> {