Auto merge of rust-lang#48516 - petrochenkov:stabsl, r=nikomatsakis

Stabilize slice patterns without `..`

And merge `feature(advanced_slice_patterns)` into `feature(slice_patterns)`.

The detailed description can be found in rust-lang#48836.

Slice patterns were unstable for long time since before 1.0 due to many bugs in the implementation, now this stabilization is possible primarily due to work of @arielb1 who [wrote the new MIR-based implementation of slice patterns](rust-lang#32202) and @mikhail-m1 who [fixed one remaining class of codegen issues](rust-lang#47926).

Reference PR rust-lang/reference#259
cc rust-lang#23121
fixes rust-lang#48836

Author: bors

src/doc/unstable-book/src/language-features/advanced-slice-patterns.md

@@ -4,25 +4,29 @@ The tracking issue for this feature is: [#23121]
 
 [#23121]: https://github.com/rust-lang/rust/issues/23121
 
-See also
-[`advanced_slice_patterns`](language-features/advanced-slice-patterns.html).
-
 ------------------------
 
-
-If you want to match against a slice or array, you can use `&` with the
-`slice_patterns` feature:
+The `slice_patterns` feature gate lets you use `..` to indicate any number of
+elements inside a pattern matching a slice. This wildcard can only be used once
+for a given array. If there's an pattern before the `..`, the subslice will be
+matched against that pattern. For example:
 
 ```rust
 #![feature(slice_patterns)]
 
+fn is_symmetric(list: &[u32]) -> bool {
+    match list {
+        &[] | &[_] => true,
+        &[x, ref inside.., y] if x == y => is_symmetric(inside),
+        &[..] => false,
+    }
+}
+
 fn main() {
-    let v = vec!["match_this", "1"];
+    let sym = &[0, 1, 4, 2, 4, 1, 0];
+    assert!(is_symmetric(sym));
 
-    match &v[..] {
-        &["match_this", second] => println!("The second element is {}", second),
-        _ => {},
-    }
+    let not_sym = &[0, 1, 7, 2, 4, 1, 0];
+    assert!(!is_symmetric(not_sym));
 }
 ```
-

src/doc/unstable-book/src/language-features/slice-patterns.md

@@ -111,7 +111,6 @@
 #![feature(ptr_internals)]
 #![feature(rustc_attrs)]
 #![feature(slice_get_slice)]
-#![feature(slice_patterns)]
 #![feature(slice_rsplit)]
 #![feature(specialization)]
 #![feature(staged_api)]

src/liballoc/lib.rs

@@ -11,7 +11,6 @@
 #![deny(warnings)]
 
 #![feature(flt2dec)]
-#![feature(slice_patterns)]
 #![feature(test)]
 
 extern crate core;

src/libcore/benches/lib.rs

@@ -37,6 +37,7 @@
 #![feature(raw)]
 #![feature(refcell_replace_swap)]
 #![feature(slice_patterns)]
+#![feature(slice_rotate)]
 #![feature(sort_internals)]
 #![feature(specialization)]
 #![feature(step_trait)]

src/libcore/tests/lib.rs

@@ -10,7 +10,6 @@
 
 #![deny(warnings)]
 
-#![feature(slice_patterns)]
 #![feature(test)]
 
 extern crate test;

src/librustc/benches/lib.rs

@@ -47,7 +47,7 @@
 #![forbid(unsafe_code)]
 
 #![feature(i128_type)]
-#![feature(slice_patterns)]
+#![cfg_attr(stage0, feature(slice_patterns))]
 #![feature(try_from)]
 
 // See librustc_cratesio_shim/Cargo.toml for a comment explaining this.

src/librustc_apfloat/lib.rs

@@ -20,7 +20,6 @@
 #![deny(warnings)]
 
 #![feature(rustc_diagnostic_macros)]
-#![feature(slice_patterns)]
 #![feature(box_patterns)]
 #![feature(box_syntax)]
 #![feature(macro_lifetime_matcher)]

src/librustc_const_eval/lib.rs

@@ -31,7 +31,6 @@
 #![feature(macro_vis_matcher)]
 #![feature(quote)]
 #![feature(rustc_diagnostic_macros)]
-#![feature(slice_patterns)]
 #![cfg_attr(stage0, feature(never_type))]
 
 #[macro_use]

src/librustc_lint/lib.rs

@@ -30,7 +30,7 @@
 #![feature(libc)]
 #![feature(quote)]
 #![feature(rustc_diagnostic_macros)]
-#![feature(slice_patterns)]
+#![cfg_attr(stage0, feature(slice_patterns))]
 #![feature(conservative_impl_trait)]
 #![feature(optin_builtin_traits)]
 #![feature(inclusive_range_fields)]