stabilise feature(never_type)

Replace feature(never_type) with feature(exhaustive_patterns).
feature(exhaustive_patterns) only covers the pattern-exhaustives checks
that used to be covered by feature(never_type)

Author: canndrew

src/libcore/cmp.rs

@@ -880,24 +880,24 @@ mod impls {
 
     ord_impl! { char usize u8 u16 u32 u64 u128 isize i8 i16 i32 i64 i128 }
 
-    #[unstable(feature = "never_type", issue = "35121")]
+    #[stable(feature = "never_type", since = "1.24.0")]
     impl PartialEq for ! {
         fn eq(&self, _: &!) -> bool {
             *self
         }
     }
 
-    #[unstable(feature = "never_type", issue = "35121")]
+    #[stable(feature = "never_type", since = "1.24.0")]
     impl Eq for ! {}
 
-    #[unstable(feature = "never_type", issue = "35121")]
+    #[stable(feature = "never_type", since = "1.24.0")]
     impl PartialOrd for ! {
         fn partial_cmp(&self, _: &!) -> Option<Ordering> {
             *self
         }
     }
 
-    #[unstable(feature = "never_type", issue = "35121")]
+    #[stable(feature = "never_type", since = "1.24.0")]
     impl Ord for ! {
         fn cmp(&self, _: &!) -> Ordering {
             *self

src/libcore/fmt/mod.rs

@@ -1575,14 +1575,14 @@ macro_rules! fmt_refs {
 
 fmt_refs! { Debug, Display, Octal, Binary, LowerHex, UpperHex, LowerExp, UpperExp }
 
-#[unstable(feature = "never_type", issue = "35121")]
+#[stable(feature = "never_type", since = "1.24.0")]
 impl Debug for ! {
     fn fmt(&self, _: &mut Formatter) -> Result {
         *self
     }
 }
 
-#[unstable(feature = "never_type", issue = "35121")]
+#[stable(feature = "never_type", since = "1.24.0")]
 impl Display for ! {
     fn fmt(&self, _: &mut Formatter) -> Result {
         *self

src/libcore/lib.rs

@@ -78,7 +78,7 @@
 #![feature(inclusive_range_syntax)]
 #![feature(intrinsics)]
 #![feature(lang_items)]
-#![feature(never_type)]
+#![feature(exhaustive_patterns)]
 #![feature(no_core)]
 #![feature(on_unimplemented)]
 #![feature(optin_builtin_traits)]
@@ -92,6 +92,7 @@
 #![feature(unwind_attributes)]
 #![feature(doc_spotlight)]
 #![feature(rustc_const_unstable)]
+#![cfg_attr(stage0, feature(never_type))]
 
 #[prelude_import]
 #[allow(unused)]

src/librustc/lib.rs

@@ -57,7 +57,7 @@
 #![cfg_attr(windows, feature(libc))]
 #![feature(macro_vis_matcher)]
 #![feature(match_default_bindings)]
-#![feature(never_type)]
+#![feature(exhaustive_patterns)]
 #![feature(non_exhaustive)]
 #![feature(nonzero)]
 #![feature(quote)]

src/librustc_const_eval/_match.rs

@@ -201,7 +201,7 @@ impl<'a, 'tcx> MatchCheckCtxt<'a, 'tcx> {
     }
 
     fn is_uninhabited(&self, ty: Ty<'tcx>) -> bool {
-        if self.tcx.sess.features.borrow().never_type {
+        if self.tcx.sess.features.borrow().exhaustive_patterns {
             self.tcx.is_ty_uninhabited_from(self.module, ty)
         } else {
             false
@@ -227,7 +227,7 @@ impl<'a, 'tcx> MatchCheckCtxt<'a, 'tcx> {
                               substs: &'tcx ty::subst::Substs<'tcx>)
                               -> bool
     {
-        if self.tcx.sess.features.borrow().never_type {
+        if self.tcx.sess.features.borrow().exhaustive_patterns {
             self.tcx.is_enum_variant_uninhabited_from(self.module, variant, substs)
         } else {
             false
@@ -661,7 +661,7 @@ pub fn is_useful<'p, 'a: 'p, 'tcx: 'a>(cx: &mut MatchCheckCtxt<'a, 'tcx>,
         // test for details.
         //
         // FIXME: currently the only way I know of something can
-        // be a privately-empty enum is when the never_type
+        // be a privately-empty enum is when the exhaustive_patterns
         // feature flag is not present, so this is only
         // needed for that case.
 

src/librustc_const_eval/check_match.rs

@@ -212,7 +212,9 @@ impl<'a, 'tcx> MatchVisitor<'a, 'tcx> {
             let pat_ty = self.tables.node_id_to_type(scrut.hir_id);
             let module = self.tcx.hir.get_module_parent(scrut.id);
             if inlined_arms.is_empty() {
-                let scrutinee_is_uninhabited = if self.tcx.sess.features.borrow().never_type {
+                let scrutinee_is_uninhabited = if self.tcx.sess.features
+                                                               .borrow()
+                                                               .exhaustive_patterns {
                     self.tcx.is_ty_uninhabited_from(module, pat_ty)
                 } else {
                     self.conservative_is_uninhabited(pat_ty)

src/librustc_lint/lib.rs

@@ -32,6 +32,7 @@
 #![feature(quote)]
 #![feature(rustc_diagnostic_macros)]
 #![feature(slice_patterns)]
+#![cfg_attr(stage0, feature(never_type))]
 
 #[macro_use]
 extern crate syntax;

src/librustc_mir/build/matches/simplify.rs

@@ -113,7 +113,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
             PatternKind::Variant { adt_def, substs, variant_index, ref subpatterns } => {
                 let irrefutable = adt_def.variants.iter().enumerate().all(|(i, v)| {
                     i == variant_index || {
-                        self.hir.tcx().sess.features.borrow().never_type &&
+                        self.hir.tcx().sess.features.borrow().exhaustive_patterns &&
                         self.hir.tcx().is_variant_uninhabited_from_all_modules(v, substs)
                     }
                 });

src/librustc_mir/lib.rs

@@ -30,13 +30,14 @@ Rust MIR: a lowered representation of Rust. Also: an experiment!
 #![feature(inclusive_range)]
 #![feature(macro_vis_matcher)]
 #![feature(match_default_bindings)]
-#![feature(never_type)]
+#![feature(exhaustive_patterns)]
 #![feature(range_contains)]
 #![feature(rustc_diagnostic_macros)]
 #![feature(placement_in_syntax)]
 #![feature(collection_placement)]
 #![feature(nonzero)]
 #![feature(underscore_lifetimes)]
+#![cfg_attr(stage0, feature(never_type))]
 
 #[macro_use]
 extern crate bitflags;

src/librustc_typeck/lib.rs

@@ -80,12 +80,13 @@ This API is completely unstable and subject to change.
 #![feature(crate_visibility_modifier)]
 #![feature(from_ref)]
 #![feature(match_default_bindings)]
-#![feature(never_type)]
+#![feature(exhaustive_patterns)]
 #![feature(option_filter)]
 #![feature(quote)]
 #![feature(refcell_replace_swap)]
 #![feature(rustc_diagnostic_macros)]
 #![feature(slice_patterns)]
+#![cfg_attr(stage0, feature(never_type))]
 
 #[macro_use] extern crate log;
 #[macro_use] extern crate syntax;

src/libstd/error.rs

@@ -234,7 +234,7 @@ impl<'a> From<Cow<'a, str>> for Box<Error> {
     }
 }
 
-#[unstable(feature = "never_type", issue = "35121")]
+#[stable(feature = "never_type", since = "1.24.0")]
 impl Error for ! {
     fn description(&self) -> &str { *self }
 }

src/libstd/lib.rs

@@ -283,7 +283,7 @@
 #![feature(macro_reexport)]
 #![feature(macro_vis_matcher)]
 #![feature(needs_panic_runtime)]
-#![feature(never_type)]
+#![feature(exhaustive_patterns)]
 #![feature(num_bits_bytes)]
 #![feature(old_wrapping)]
 #![feature(on_unimplemented)]
@@ -324,6 +324,7 @@
 #![cfg_attr(test, feature(update_panic_count))]
 #![cfg_attr(windows, feature(used))]
 #![cfg_attr(stage0, feature(repr_align))]
+#![cfg_attr(stage0, feature(never_type))]
 
 #![default_lib_allocator]
 

src/libstd/primitive_docs.rs

@@ -79,7 +79,6 @@ mod prim_bool { }
 /// write:
 ///
 /// ```
-/// #![feature(never_type)]
 /// # fn foo() -> u32 {
 /// let x: ! = {
 ///     return 123
@@ -131,13 +130,15 @@ mod prim_bool { }
 /// [`Result<String, !>`] which we can unpack like this:
 ///
 /// ```ignore (string-from-str-error-type-is-not-never-yet)
+/// #[feature(exhaustive_patterns)]
 /// // NOTE: This does not work today!
 /// let Ok(s) = String::from_str("hello");
 /// ```
 ///
-/// Since the [`Err`] variant contains a `!`, it can never occur. So we can exhaustively match on
-/// [`Result<T, !>`] by just taking the [`Ok`] variant. This illustrates another behaviour of `!` -
-/// it can be used to "delete" certain enum variants from generic types like `Result`.
+/// Since the [`Err`] variant contains a `!`, it can never occur. If the `exhaustive_patterns`
+/// feature is present this means we can exhaustively match on [`Result<T, !>`] by just taking the
+/// [`Ok`] variant. This illustrates another behaviour of `!` - it can be used to "delete" certain
+/// enum variants from generic types like `Result`.
 ///
 /// [`String::from_str`]: str/trait.FromStr.html#tymethod.from_str
 /// [`Result<String, !>`]: result/enum.Result.html
@@ -154,7 +155,6 @@ mod prim_bool { }
 /// for example:
 ///
 /// ```
-/// # #![feature(never_type)]
 /// # use std::fmt;
 /// # trait Debug {
 /// # fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result;
@@ -192,7 +192,6 @@ mod prim_bool { }
 /// [`Default`]: default/trait.Default.html
 /// [`default()`]: default/trait.Default.html#tymethod.default
 ///
-#[unstable(feature = "never_type", issue = "35121")]
 mod prim_never { }
 
 #[doc(primitive = "char")]

src/libsyntax/feature_gate.rs

@@ -280,8 +280,8 @@ declare_features! (
     // Allows `impl Trait` in function arguments.
     (active, universal_impl_trait, "1.23.0", Some(34511)),
 
-    // The `!` type
-    (active, never_type, "1.13.0", Some(35121)),
+    // Allows exhaustive pattern matching on types that contain uninhabited types.
+    (active, exhaustive_patterns, "1.13.0", None),
 
     // Allows all literals in attribute lists and values of key-value pairs.
     (active, attr_literals, "1.13.0", Some(34981)),
@@ -1617,10 +1617,6 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
             ast::TyKind::BareFn(ref bare_fn_ty) => {
                 self.check_abi(bare_fn_ty.abi, ty.span);
             }
-            ast::TyKind::Never => {
-                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");

src/test/compile-fail/call-fn-never-arg-wrong-type.rs

@@ -10,8 +10,6 @@
 
 // Test that we can't pass other types for !
 
-#![feature(never_type)]
-
 fn foo(x: !) -> ! {
     x
 }

src/test/compile-fail/coerce-to-bang-cast.rs

@@ -8,8 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(never_type)]
-
 fn foo(x: usize, y: !, z: usize) { }
 
 #[deny(coerce_never)]

src/test/compile-fail/coerce-to-bang.rs

@@ -8,7 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(never_type)]
 #![deny(coerce_never)]
 
 fn foo(x: usize, y: !, z: usize) { }

src/test/compile-fail/inhabitedness-infinite-loop.rs

@@ -10,7 +10,7 @@
 
 // error-pattern:reached recursion limit
 
-#![feature(never_type)]
+#![feature(exhaustive_patterns)]
 
 struct Foo<'a, T: 'a> {
     ph: std::marker::PhantomData<T>,

src/test/compile-fail/loop-break-value.rs

@@ -8,8 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(never_type)]
-
 fn main() {
     let val: ! = loop { break break; };
     //~^ ERROR mismatched types

src/test/compile-fail/match-privately-empty.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(never_type)]
+#![feature(exhaustive_patterns)]
 
 mod private {
     pub struct Private {

src/test/compile-fail/never-assign-dead-code.rs

@@ -10,7 +10,7 @@
 
 // Test that an assignment of type ! makes the rest of the block dead code.
 
-#![feature(never_type, rustc_attrs)]
+#![feature(rustc_attrs)]
 #![warn(unused)]
 
 #[rustc_error]

src/test/compile-fail/never-assign-wrong-type.rs

@@ -10,7 +10,6 @@
 
 // Test that we can't use another type in place of !
 
-#![feature(never_type)]
 #![deny(warnings)]
 
 fn main() {

src/test/compile-fail/recursive-types-are-not-uninhabited.rs

@@ -8,8 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-//#![feature(never_type)]
-
 struct R<'a> {
     r: &'a R<'a>,
 }

src/test/compile-fail/uninhabited-irrefutable.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(never_type)]
+#![feature(exhaustive_patterns)]
 
 mod foo {
     pub struct SecretlyEmpty {

src/test/compile-fail/uninhabited-patterns.rs

@@ -11,7 +11,7 @@
 #![feature(box_patterns)]
 #![feature(slice_patterns)]
 #![feature(box_syntax)]
-#![feature(never_type)]
+#![feature(exhaustive_patterns)]
 #![deny(unreachable_patterns)]
 
 mod foo {

src/test/compile-fail/unreachable-loop-patterns.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(never_type)]
+#![feature(exhaustive_patterns)]
 #![deny(unreachable_patterns)]
 
 fn main() {

src/test/compile-fail/unreachable-try-pattern.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(never_type, rustc_attrs)]
+#![feature(exhaustive_patterns, rustc_attrs)]
 #![warn(unreachable_code)]
 #![warn(unreachable_patterns)]
 

src/test/run-fail/adjust_never.rs

@@ -10,8 +10,6 @@
 
 // Test that a variable of type ! can coerce to another type.
 
-#![feature(never_type)]
-
 // error-pattern:explicit
 fn main() {
     let x: ! = panic!();

src/test/run-fail/call-fn-never-arg.rs

@@ -12,7 +12,6 @@
 
 // error-pattern:wowzers!
 
-#![feature(never_type)]
 #![allow(unreachable_code)]
 
 fn foo(x: !) -> ! {

src/test/run-fail/cast-never.rs

@@ -10,8 +10,6 @@
 
 // Test that we can explicitly cast ! to another type
 
-#![feature(never_type)]
-
 // error-pattern:explicit
 fn main() {
     let x: ! = panic!();

src/test/run-fail/never-associated-type.rs

@@ -10,8 +10,6 @@
 
 // Test that we can use ! as an associated type.
 
-#![feature(never_type)]
-
 // error-pattern:kapow!
 
 trait Foo {