Auto merge of #39265 - est31:master, r=petrochenkov

Stabilize static lifetime in statics

Stabilize the "static_in_const" feature. Blockers before this PR can be merged:

* [x] The [FCP with inclination to stabilize](#35897 (comment)) needs to be over. FCP lasts roughly three weeks, so will be over at Jan 25, aka this thursday.
* [x] Documentation needs to be added (#37928)

Closes #35897.

src/librustc/middle/resolve_lifetime.rs

@@ -238,8 +238,6 @@ enum Elide {
  FreshLateAnon(Cell<u32>),
  /// Always use this one lifetime.
  Exact(Region),
- /// Like `Exact(Static)` but requires `#![feature(static_in_const)]`.
- Static,
  /// Less or more than one lifetime were found, error on unspecified.
  Error(Vec<ElisionFailureInfo>)
 }
@@ -324,7 +322,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
  hir::ItemConst(..) => {
  // No lifetime parameters, but implied 'static.
  let scope = Scope::Elision {
- elide: Elide::Static,
+ elide: Elide::Exact(Region::Static),
  s: ROOT_SCOPE
  };
  self.with(scope, |_, this| intravisit::walk_item(this, item));
@@ -1307,16 +1305,6 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
  return;
  }
  Elide::Exact(l) => l.shifted(late_depth),
- Elide::Static => {
- if !self.sess.features.borrow().static_in_const {
- self.sess
- .struct_span_err(span,
- "this needs a `'static` lifetime or the \
- `static_in_const` feature, see #35897")
- .emit();
- }
- Region::Static
- }
  Elide::Error(ref e) => break Some(e)
  };
  for lifetime_ref in lifetime_refs {

src/libsyntax/feature_gate.rs

@@ -281,9 +281,6 @@ declare_features! (
  // Allows untagged unions `union U { ... }`
  (active, untagged_unions, "1.13.0", Some(32836)),
 
- // elide `'static` lifetimes in `static`s and `const`s
- (active, static_in_const, "1.13.0", Some(35897)),
-
  // Used to identify the `compiler_builtins` crate
  // rustc internal
  (active, compiler_builtins, "1.13.0", None),
@@ -386,6 +383,8 @@ declare_features! (
  (accepted, item_like_imports, "1.14.0", Some(35120)),
  // Allows using `Self` and associated types in struct expressions and patterns.
  (accepted, more_struct_aliases, "1.16.0", Some(37544)),
+ // elide `'static` lifetimes in `static`s and `const`s
+ (accepted, static_in_const, "1.17.0", Some(35897)),
 );
 // (changing above list without updating src/doc/reference.md makes @cmr sad)
 

src/test/compile-fail/rfc1623.rs

@@ -7,7 +7,6 @@
 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
-#![feature(static_in_const)]
 #![allow(dead_code)]
 
 fn non_elidable<'a, 'b>(a: &'a u8, b: &'b u8) -> &'a u8 {

src/test/incremental/change_add_field/struct_point.rs

@@ -18,7 +18,6 @@
 
 #![feature(rustc_attrs)]
 #![feature(stmt_expr_attributes)]
-#![feature(static_in_const)]
 #![allow(dead_code)]
 
 // These are expected to require translation.

src/test/incremental/change_pub_inherent_method_sig/struct_point.rs

@@ -15,7 +15,6 @@
 
 #![feature(rustc_attrs)]
 #![feature(stmt_expr_attributes)]
-#![feature(static_in_const)]
 #![allow(dead_code)]
 
 // These are expected to require translation.

src/test/run-pass/rfc1623.rs

@@ -8,7 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(static_in_const)]
 #![allow(dead_code)]
 
 // very simple test for a 'static static with default lifetime