Rollup merge of #49968 - christianpoveda:stabilize_dyn, r=nikomatsakis

Stabilize dyn trait

This PR stabilizes RFC 2113. I followed the [stabilization guide](https://forge.rust-lang.org/stabilization-guide.html).

Related issue: #49218

Author: kennytm

src/librustc/hir/lowering.rs

@@ -4107,15 +4107,13 @@ impl<'a> LoweringContext<'a> {
     }
 
     fn maybe_lint_bare_trait(&self, span: Span, id: NodeId, is_global: bool) {
-        if self.sess.features_untracked().dyn_trait {
-            self.sess.buffer_lint_with_diagnostic(
-                builtin::BARE_TRAIT_OBJECT,
-                id,
-                span,
-                "trait objects without an explicit `dyn` are deprecated",
-                builtin::BuiltinLintDiagnostics::BareTraitObject(span, is_global),
-            )
-        }
+        self.sess.buffer_lint_with_diagnostic(
+            builtin::BARE_TRAIT_OBJECT,
+            id,
+            span,
+            "trait objects without an explicit `dyn` are deprecated",
+            builtin::BuiltinLintDiagnostics::BareTraitObject(span, is_global),
+        )
     }
 
     fn wrap_in_try_constructor(

src/librustc/lib.rs

@@ -45,8 +45,8 @@
 #![feature(const_fn)]
 #![feature(core_intrinsics)]
 #![feature(drain_filter)]
-#![feature(dyn_trait)]
 #![feature(entry_or_default)]
+#![cfg_attr(stage0, feature(dyn_trait))]
 #![feature(from_ref)]
 #![feature(fs_read_write)]
 #![cfg_attr(windows, feature(libc))]

src/librustc_mir/lib.rs

@@ -24,7 +24,7 @@ Rust MIR: a lowered representation of Rust. Also: an experiment!
 #![feature(const_fn)]
 #![feature(core_intrinsics)]
 #![feature(decl_macro)]
-#![feature(dyn_trait)]
+#![cfg_attr(stage0, feature(dyn_trait))]
 #![feature(fs_read_write)]
 #![feature(macro_vis_matcher)]
 #![feature(exhaustive_patterns)]

src/librustc_typeck/lib.rs

@@ -71,6 +71,8 @@ This API is completely unstable and subject to change.
 
 #![allow(non_camel_case_types)]
 
+#![cfg_attr(stage0, feature(dyn_trait))]
+
 #![feature(box_patterns)]
 #![feature(box_syntax)]
 #![feature(crate_visibility_modifier)]
@@ -81,7 +83,6 @@ This API is completely unstable and subject to change.
 #![feature(rustc_diagnostic_macros)]
 #![feature(slice_patterns)]
 #![feature(slice_sort_by_cached_key)]
-#![feature(dyn_trait)]
 #![feature(never_type)]
 
 #[macro_use] extern crate log;

src/librustdoc/lib.rs

@@ -13,6 +13,8 @@
        html_root_url = "https://doc.rust-lang.org/nightly/",
        html_playground_url = "https://play.rust-lang.org/")]
 
+#![cfg_attr(stage0, feature(dyn_trait))]
+
 #![feature(ascii_ctype)]
 #![feature(rustc_private)]
 #![feature(box_patterns)]
@@ -23,7 +25,6 @@
 #![feature(test)]
 #![feature(vec_remove_item)]
 #![feature(entry_and_modify)]
-#![feature(dyn_trait)]
 
 extern crate arena;
 extern crate getopts;

src/libsyntax/feature_gate.rs

@@ -375,9 +375,6 @@ declare_features! (
     // Future-proofing enums/structs with #[non_exhaustive] attribute (RFC 2008)
     (active, non_exhaustive, "1.22.0", Some(44109), None),
 
-    // Trait object syntax with `dyn` prefix
-    (active, dyn_trait, "1.22.0", Some(44662), Some(Edition::Edition2018)),
-
     // `crate` as visibility modifier, synonymous to `pub(crate)`
     (active, crate_visibility_modifier, "1.23.0", Some(45388), Some(Edition::Edition2018)),
 
@@ -592,6 +589,8 @@ declare_features! (
     (accepted, cfg_target_feature, "1.27.0", Some(29717), None),
     // Allows #[target_feature(...)]
     (accepted, target_feature, "1.27.0", None, None),
+    // Trait object syntax with `dyn` prefix
+    (accepted, dyn_trait, "1.27.0", Some(44662), None),
 );
 
 // If you change this, please modify src/doc/unstable-book as well. You must
@@ -1657,10 +1656,6 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
                 gate_feature_post!(&self, never_type, ty.span,
                                    "The `!` type is experimental");
             }
-            ast::TyKind::TraitObject(_, ast::TraitObjectSyntax::Dyn) => {
-                gate_feature_post!(&self, dyn_trait, ty.span,
-                                   "`dyn Trait` syntax is unstable");
-            }
             _ => {}
         }
         visit::walk_ty(self, ty)

src/test/compile-fail/impl-trait/where-allowed.rs

@@ -10,7 +10,6 @@
 
 //! A simple test for testing many permutations of allowedness of
 //! impl Trait
-#![feature(dyn_trait)]
 use std::fmt::Debug;
 
 // Allowed

src/test/compile-fail/mir_check_cast_unsize.rs

@@ -11,7 +11,6 @@
 // compile-flags: -Z borrowck=mir
 
 #![allow(dead_code)]
-#![feature(dyn_trait)]
 
 use std::fmt::Debug;
 

src/test/compile-fail/trait-bounds-not-on-struct.rs

@@ -8,7 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(dyn_trait)]
 #![allow(bare_trait_object)]
 
 struct Foo;

src/test/run-fail/rfc-1937-termination-trait/termination-trait-for-box-dyn-error.rs

@@ -11,8 +11,6 @@
 // compile-pass
 // failure-status: 1
 
-#![feature(dyn_trait)]
-
 use std::error::Error;
 use std::io;