Rollup merge of #64639 - davidtwco:rfc-2008-stabilization, r=Centril

Stabilize `#[non_exhaustive]` (RFC 2008)

Fixes #44109.

This pull request stabilizes the `#[non_exhaustive]` attribute, which is used to indicate that a type will have more fields / variants added in the future. It can be applied to `struct`s, `enum`s and `enum` variants. See #44109 (comment) for the stabilization report.

r? @Centril

Author: Centril

src/doc/unstable-book/src/language-features/non-exhaustive.md

@@ -121,7 +121,7 @@
 #![feature(hexagon_target_feature)]
 #![feature(const_int_conversion)]
 #![feature(const_transmute)]
-#![feature(non_exhaustive)]
+#![cfg_attr(bootstrap, feature(non_exhaustive))]
 #![feature(structural_match)]
 #![feature(abi_unadjusted)]
 #![feature(adx_target_feature)]

src/libcore/lib.rs

@@ -25,7 +25,7 @@
 #![feature(extern_types)]
 #![feature(in_band_lifetimes)]
 #![feature(optin_builtin_traits)]
-#![feature(non_exhaustive)]
+#![cfg_attr(bootstrap, feature(non_exhaustive))]
 #![feature(rustc_attrs)]
 #![feature(specialization)]
 

src/libproc_macro/lib.rs

@@ -2105,8 +2105,6 @@ on something other than a struct or enum.
 Examples of erroneous code:
 
 ```compile_fail,E0701
-# #![feature(non_exhaustive)]
-
 #[non_exhaustive]
 trait Foo { }
 ```

src/librustc/error_codes.rs

@@ -41,7 +41,7 @@
 #![feature(overlapping_marker_traits)]
 #![feature(extern_types)]
 #![feature(nll)]
-#![feature(non_exhaustive)]
+#![cfg_attr(bootstrap, feature(non_exhaustive))]
 #![feature(optin_builtin_traits)]
 #![feature(option_expect_none)]
 #![feature(range_is_empty)]

src/librustc/lib.rs

@@ -283,7 +283,7 @@
 #![feature(needs_panic_runtime)]
 #![feature(never_type)]
 #![feature(nll)]
-#![feature(non_exhaustive)]
+#![cfg_attr(bootstrap, feature(non_exhaustive))]
 #![feature(on_unimplemented)]
 #![feature(optin_builtin_traits)]
 #![feature(panic_info_message)]

src/libstd/lib.rs

@@ -245,8 +245,10 @@ declare_features! (
     (accepted, bind_by_move_pattern_guards, "1.39.0", Some(15287), None),
     /// Allows attributes in formal function parameters.
     (accepted, param_attrs, "1.39.0", Some(60406), None),
-    // Allows macro invocations in `extern {}` blocks.
+    /// Allows macro invocations in `extern {}` blocks.
     (accepted, macros_in_extern, "1.40.0", Some(49476), None),
+    /// Allows future-proofing enums/structs with the `#[non_exhaustive]` attribute (RFC 2008).
+    (accepted, non_exhaustive, "1.40.0", Some(44109), None),
 
     // -------------------------------------------------------------------------
     // feature-group-end: accepted features

src/libsyntax/feature_gate/accepted.rs

@@ -383,9 +383,6 @@ declare_features! (
     /// Allows `#[doc(include = "some-file")]`.
     (active, external_doc, "1.22.0", Some(44732), None),
 
-    /// Allows future-proofing enums/structs with the `#[non_exhaustive]` attribute (RFC 2008).
-    (active, non_exhaustive, "1.22.0", Some(44109), None),
-
     /// Allows using `crate` as visibility modifier, synonymous with `pub(crate)`.
     (active, crate_visibility_modifier, "1.23.0", Some(53120), None),
 

src/libsyntax/feature_gate/active.rs

@@ -252,6 +252,7 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
     ungated!(path, Normal, template!(NameValueStr: "file")),
     ungated!(no_std, CrateLevel, template!(Word)),
     ungated!(no_implicit_prelude, Normal, template!(Word)),
+    ungated!(non_exhaustive, Whitelisted, template!(Word)),
 
     // Runtime
     ungated!(windows_subsystem, Whitelisted, template!(NameValueStr: "windows|console")),
@@ -314,9 +315,6 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
         test_runner, CrateLevel, template!(List: "path"), custom_test_frameworks,
         "custom test frameworks are an unstable feature",
     ),
-
-    // RFC #2008
-    gated!(non_exhaustive, Whitelisted, template!(Word), experimental!(non_exhaustive)),
     // RFC #1268
     gated!(marker, Normal, template!(Word), marker_trait_attr, experimental!(marker)),
     gated!(

src/libsyntax/feature_gate/builtin_attrs.rs

@@ -9,7 +9,7 @@
 #![feature(const_fn)]
 #![feature(crate_visibility_modifier)]
 #![feature(nll)]
-#![feature(non_exhaustive)]
+#![cfg_attr(bootstrap, feature(non_exhaustive))]
 #![feature(optin_builtin_traits)]
 #![feature(rustc_attrs)]
 #![cfg_attr(bootstrap, feature(proc_macro_hygiene))]

src/libsyntax_pos/lib.rs

@@ -1,5 +1,4 @@
 #![crate_type = "rlib"]
-#![feature(non_exhaustive)]
 
 #[non_exhaustive]
 pub enum NonExhaustiveEnum {

src/test/ui/feature-gates/feature-gate-non_exhaustive.rs

@@ -1,5 +1,3 @@
-#![feature(non_exhaustive)]
-
 #[non_exhaustive]
 pub struct NormalStruct {
     pub first_field: u16,

src/test/ui/feature-gates/feature-gate-non_exhaustive.stderr

@@ -1,5 +1,4 @@
 #![crate_type = "rlib"]
-#![feature(non_exhaustive)]
 
 pub enum NonExhaustiveVariants {
     #[non_exhaustive] Unit,

src/test/ui/rfc-2008-non-exhaustive/auxiliary/enums.rs

@@ -1,7 +1,5 @@
 // run-pass
 
-#![feature(non_exhaustive)]
-
 #[non_exhaustive]
 pub enum NonExhaustiveEnum {
     Unit,

src/test/ui/rfc-2008-non-exhaustive/auxiliary/structs.rs

@@ -1,5 +1,3 @@
-#![feature(non_exhaustive)]
-
 #[non_exhaustive]
 #[repr(C)]
 pub enum NonExhaustiveEnum {

src/test/ui/rfc-2008-non-exhaustive/auxiliary/variants.rs

@@ -1,5 +1,4 @@
 // check-pass
-#![feature(non_exhaustive)]
 #![deny(improper_ctypes)]
 
 // This test checks that non-exhaustive types with `#[repr(C)]` are considered proper within

src/test/ui/rfc-2008-non-exhaustive/enum_same_crate.rs

@@ -1,5 +1,3 @@
-#![feature(non_exhaustive)]
-
 #[non_exhaustive(anything)]
 //~^ ERROR malformed `non_exhaustive` attribute
 struct Foo;

src/test/ui/rfc-2008-non-exhaustive/improper_ctypes/auxiliary/types.rs

@@ -1,11 +1,11 @@
 error: malformed `non_exhaustive` attribute input
-  --> $DIR/invalid-attribute.rs:3:1
+  --> $DIR/invalid-attribute.rs:1:1
    |
 LL | #[non_exhaustive(anything)]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: must be of the form: `#[non_exhaustive]`
 
 error[E0701]: attribute can only be applied to a struct or enum
-  --> $DIR/invalid-attribute.rs:7:1
+  --> $DIR/invalid-attribute.rs:5:1
    |
 LL | #[non_exhaustive]
    | ^^^^^^^^^^^^^^^^^
@@ -14,7 +14,7 @@ LL | trait Bar { }
    | ------------- not a struct or enum
 
 error[E0701]: attribute can only be applied to a struct or enum
-  --> $DIR/invalid-attribute.rs:11:1
+  --> $DIR/invalid-attribute.rs:9:1
    |
 LL |   #[non_exhaustive]
    |   ^^^^^^^^^^^^^^^^^

src/test/ui/rfc-2008-non-exhaustive/improper_ctypes/same_crate_proper.rs

@@ -16,7 +16,7 @@ error[E0603]: tuple struct constructor `TupleStruct` is private
 LL |     let ts_explicit = structs::TupleStruct(640, 480);
    |                                ^^^^^^^^^^^
    | 
-  ::: $DIR/auxiliary/structs.rs:13:24
+  ::: $DIR/auxiliary/structs.rs:11:24
    |
 LL | pub struct TupleStruct(pub u16, pub u16);
    |                        ---------------- a constructor is private if any of the fields is private

src/test/ui/rfc-2008-non-exhaustive/invalid-attribute.rs

@@ -1,7 +1,6 @@
 // run-pass
 
 #![allow(unused_variables)]
-#![feature(non_exhaustive)]
 
 #[non_exhaustive]
 pub struct NormalStruct {

src/test/ui/rfc-2008-non-exhaustive/invalid-attribute.stderr

@@ -1,6 +1,5 @@
 #![crate_type = "rlib"]
 #![feature(never_type)]
-#![feature(non_exhaustive)]
 
 #[non_exhaustive]
 pub enum UninhabitedEnum {

src/test/ui/rfc-2008-non-exhaustive/struct.stderr

@@ -1,5 +1,4 @@
 #![feature(never_type)]
-#![feature(non_exhaustive)]
 
 #[non_exhaustive]
 pub enum UninhabitedEnum {

src/test/ui/rfc-2008-non-exhaustive/structs_same_crate.rs

@@ -1,5 +1,5 @@
 error[E0308]: mismatched types
-  --> $DIR/coercions_same_crate.rs:31:5
+  --> $DIR/coercions_same_crate.rs:30:5
    |
 LL | fn cannot_coerce_empty_enum_to_anything(x: UninhabitedEnum) -> A {
    |                                                                - expected `A` because of return type
@@ -10,7 +10,7 @@ LL |     x
               found type `UninhabitedEnum`
 
 error[E0308]: mismatched types
-  --> $DIR/coercions_same_crate.rs:35:5
+  --> $DIR/coercions_same_crate.rs:34:5
    |
 LL | fn cannot_coerce_empty_tuple_struct_to_anything(x: UninhabitedTupleStruct) -> A {
    |                                                                               - expected `A` because of return type
@@ -21,7 +21,7 @@ LL |     x
               found type `UninhabitedTupleStruct`
 
 error[E0308]: mismatched types
-  --> $DIR/coercions_same_crate.rs:39:5
+  --> $DIR/coercions_same_crate.rs:38:5
    |
 LL | fn cannot_coerce_empty_struct_to_anything(x: UninhabitedStruct) -> A {
    |                                                                    - expected `A` because of return type
@@ -32,7 +32,7 @@ LL |     x
               found type `UninhabitedStruct`
 
 error[E0308]: mismatched types
-  --> $DIR/coercions_same_crate.rs:43:5
+  --> $DIR/coercions_same_crate.rs:42:5
    |
 LL | fn cannot_coerce_enum_with_empty_variants_to_anything(x: UninhabitedVariants) -> A {
    |                                                                                  - expected `A` because of return type

src/test/ui/rfc-2008-non-exhaustive/uninhabited/auxiliary/uninhabited.rs

@@ -1,5 +1,4 @@
 #![feature(never_type)]
-#![feature(non_exhaustive)]
 
 #[non_exhaustive]
 pub enum UninhabitedEnum {

src/test/ui/rfc-2008-non-exhaustive/uninhabited/coercions_same_crate.rs

@@ -1,5 +1,5 @@
 error[E0004]: non-exhaustive patterns: pattern `IndirectUninhabitedEnum` of type `IndirectUninhabitedEnum` is not handled
-  --> $DIR/indirect_match_same_crate.rs:35:11
+  --> $DIR/indirect_match_same_crate.rs:34:11
    |
 LL | pub struct IndirectUninhabitedEnum(UninhabitedEnum);
    | ----------------------------------------------------
@@ -13,7 +13,7 @@ LL |     match x {}
    = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
 
 error[E0004]: non-exhaustive patterns: pattern `IndirectUninhabitedStruct` of type `IndirectUninhabitedStruct` is not handled
-  --> $DIR/indirect_match_same_crate.rs:39:11
+  --> $DIR/indirect_match_same_crate.rs:38:11
    |
 LL | pub struct IndirectUninhabitedStruct(UninhabitedStruct);
    | --------------------------------------------------------
@@ -27,7 +27,7 @@ LL |     match x {}
    = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
 
 error[E0004]: non-exhaustive patterns: pattern `IndirectUninhabitedTupleStruct` of type `IndirectUninhabitedTupleStruct` is not handled
-  --> $DIR/indirect_match_same_crate.rs:43:11
+  --> $DIR/indirect_match_same_crate.rs:42:11
    |
 LL | pub struct IndirectUninhabitedTupleStruct(UninhabitedTupleStruct);
    | ------------------------------------------------------------------
@@ -41,7 +41,7 @@ LL |     match x {}
    = help: ensure that all possible cases are being handled, possibly by adding wildcards or more match arms
 
 error[E0004]: non-exhaustive patterns: pattern `IndirectUninhabitedVariants` of type `IndirectUninhabitedVariants` is not handled
-  --> $DIR/indirect_match_same_crate.rs:49:11
+  --> $DIR/indirect_match_same_crate.rs:48:11
    |
 LL | pub struct IndirectUninhabitedVariants(UninhabitedVariants);
    | ------------------------------------------------------------

src/test/ui/rfc-2008-non-exhaustive/uninhabited/coercions_same_crate.stderr

@@ -3,7 +3,6 @@
 #![deny(unreachable_patterns)]
 #![feature(exhaustive_patterns)]
 #![feature(never_type)]
-#![feature(non_exhaustive)]
 
 #[non_exhaustive]
 pub enum UninhabitedEnum {

src/test/ui/rfc-2008-non-exhaustive/uninhabited/indirect_match_same_crate.rs

@@ -1,7 +1,6 @@
 // aux-build:uninhabited.rs
 #![deny(unreachable_patterns)]
 #![feature(never_type)]
-#![feature(non_exhaustive)]
 
 extern crate uninhabited;
 

src/test/ui/rfc-2008-non-exhaustive/uninhabited/indirect_match_same_crate.stderr

@@ -1,5 +1,5 @@
 error: unreachable pattern
-  --> $DIR/issue-65157-repeated-match-arm.rs:16:9
+  --> $DIR/issue-65157-repeated-match-arm.rs:15:9
    |
 LL |         PartiallyInhabitedVariants::Struct { .. } => {},
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

src/test/ui/rfc-2008-non-exhaustive/uninhabited/indirect_match_with_exhaustive_patterns_same_crate.rs

@@ -1,5 +1,4 @@
 #![feature(never_type)]
-#![feature(non_exhaustive)]
 
 #[non_exhaustive]
 pub enum UninhabitedEnum {