Stabilize conservative_impl_trait

Author: cramertj

src/doc/unstable-book/src/language-features/conservative-impl-trait.md

@@ -27,7 +27,7 @@
 #![cfg_attr(stage0, feature(inclusive_range_syntax))]
 #![feature(iterator_try_fold)]
 #![feature(iterator_flatten)]
-#![feature(conservative_impl_trait)]
+#![cfg_attr(stage0, feature(conservative_impl_trait))]
 #![feature(iter_rfind)]
 #![feature(iter_rfold)]
 #![feature(iterator_repeat_with)]

src/libcore/tests/lib.rs

@@ -1789,8 +1789,6 @@ allowed as function return types.
 Erroneous code example:
 
 ```compile_fail,E0562
-#![feature(conservative_impl_trait)]
-
 fn main() {
     let count_to_ten: impl Iterator<Item=usize> = 0..10;
     // error: `impl Trait` not allowed outside of function and inherent method
@@ -1804,8 +1802,6 @@ fn main() {
 Make sure `impl Trait` only appears in return-type position.
 
 ```
-#![feature(conservative_impl_trait)]
-
 fn count_to_n(n: usize) -> impl Iterator<Item=usize> {
     0..n
 }

src/librustc/diagnostics.rs

@@ -961,16 +961,9 @@ impl<'a> LoweringContext<'a> {
                 hir::TyTraitObject(bounds, lifetime_bound)
             }
             TyKind::ImplTrait(ref bounds) => {
-                use syntax::feature_gate::{emit_feature_err, GateIssue};
                 let span = t.span;
                 match itctx {
                     ImplTraitContext::Existential => {
-                        let has_feature = self.sess.features_untracked().conservative_impl_trait;
-                        if !t.span.allows_unstable() && !has_feature {
-                            emit_feature_err(&self.sess.parse_sess, "conservative_impl_trait",
-                                             t.span, GateIssue::Language,
-                                             "`impl Trait` in return position is experimental");
-                        }
                         let def_index = self.resolver.definitions().opt_def_index(t.id).unwrap();
                         let hir_bounds = self.lower_bounds(bounds, itctx);
                         let (lifetimes, lifetime_defs) =

src/librustc/hir/lowering.rs

@@ -43,7 +43,7 @@
 
 #![feature(box_patterns)]
 #![feature(box_syntax)]
-#![feature(conservative_impl_trait)]
+#![cfg_attr(stage0, feature(conservative_impl_trait))]
 #![feature(const_fn)]
 #![feature(copy_closures, clone_closures)]
 #![feature(core_intrinsics)]

src/librustc/lib.rs

@@ -28,7 +28,7 @@
 #![feature(unsize)]
 #![feature(i128_type)]
 #![feature(i128)]
-#![feature(conservative_impl_trait)]
+#![cfg_attr(stage0, feature(conservative_impl_trait))]
 #![feature(specialization)]
 #![feature(optin_builtin_traits)]
 #![feature(underscore_lifetimes)]

src/librustc_data_structures/lib.rs

@@ -17,7 +17,7 @@
 #![allow(unused_attributes)]
 #![feature(range_contains)]
 #![cfg_attr(unix, feature(libc))]
-#![feature(conservative_impl_trait)]
+#![cfg_attr(stage0, feature(conservative_impl_trait))]
 #![feature(i128_type)]
 #![feature(optin_builtin_traits)]
 

src/librustc_errors/lib.rs

@@ -15,7 +15,7 @@
       html_root_url = "https://doc.rust-lang.org/nightly/")]
 #![deny(warnings)]
 
-#![feature(conservative_impl_trait)]
+#![cfg_attr(stage0, feature(conservative_impl_trait))]
 #![feature(fs_read_write)]
 #![feature(i128_type)]
 #![cfg_attr(stage0, feature(inclusive_range_syntax))]

src/librustc_incremental/lib.rs

@@ -14,7 +14,7 @@
 #![deny(warnings)]
 
 #![feature(box_patterns)]
-#![feature(conservative_impl_trait)]
+#![cfg_attr(stage0, feature(conservative_impl_trait))]
 #![feature(fs_read_write)]
 #![feature(i128_type)]
 #![feature(libc)]

src/librustc_metadata/lib.rs

@@ -21,7 +21,7 @@ Rust MIR: a lowered representation of Rust. Also: an experiment!
 #![feature(box_patterns)]
 #![feature(box_syntax)]
 #![feature(catch_expr)]
-#![feature(conservative_impl_trait)]
+#![cfg_attr(stage0, feature(conservative_impl_trait))]
 #![feature(const_fn)]
 #![feature(core_intrinsics)]
 #![feature(decl_macro)]