From abf2b4c04d4d6a0a2c49562fde33ae1d46e6ead7 Mon Sep 17 00:00:00 2001 From: Jacob Pratt Date: Mon, 28 Feb 2022 15:33:50 -0500 Subject: [PATCH 1/2] Stabilize `derive_default_enum` --- .../src/deriving/default.rs | 13 +---- compiler/rustc_feature/src/accepted.rs | 2 + compiler/rustc_feature/src/active.rs | 2 - compiler/rustc_feature/src/lib.rs | 2 +- compiler/rustc_infer/src/lib.rs | 2 +- compiler/rustc_middle/src/lib.rs | 2 +- compiler/rustc_session/src/lib.rs | 2 +- compiler/rustc_trait_selection/src/lib.rs | 2 +- library/core/src/lib.rs | 2 +- src/test/ui/deriving/deriving-default-enum.rs | 2 - src/test/ui/deriving/deriving-with-helper.rs | 1 - .../feature-gate-derive_default_enum.rs | 7 --- .../feature-gate-derive_default_enum.stderr | 13 ----- src/test/ui/macros/macros-nonfatal-errors.rs | 1 - .../ui/macros/macros-nonfatal-errors.stderr | 58 +++++++++---------- 15 files changed, 38 insertions(+), 73 deletions(-) delete mode 100644 src/test/ui/feature-gates/feature-gate-derive_default_enum.rs delete mode 100644 src/test/ui/feature-gates/feature-gate-derive_default_enum.stderr diff --git a/compiler/rustc_builtin_macros/src/deriving/default.rs b/compiler/rustc_builtin_macros/src/deriving/default.rs index ca83941f600..2c5260616c7 100644 --- a/compiler/rustc_builtin_macros/src/deriving/default.rs +++ b/compiler/rustc_builtin_macros/src/deriving/default.rs @@ -46,18 +46,7 @@ pub fn expand_deriving_default( StaticStruct(_, fields) => { default_struct_substructure(cx, trait_span, substr, fields) } - StaticEnum(enum_def, _) => { - if !cx.sess.features_untracked().derive_default_enum { - rustc_session::parse::feature_err( - cx.parse_sess(), - sym::derive_default_enum, - span, - "deriving `Default` on enums is experimental", - ) - .emit(); - } - default_enum_substructure(cx, trait_span, enum_def) - } + StaticEnum(enum_def, _) => default_enum_substructure(cx, trait_span, enum_def), _ => cx.span_bug(trait_span, "method in `derive(Default)`"), } })), diff --git a/compiler/rustc_feature/src/accepted.rs b/compiler/rustc_feature/src/accepted.rs index e37251c9c24..048039343a7 100644 --- a/compiler/rustc_feature/src/accepted.rs +++ b/compiler/rustc_feature/src/accepted.rs @@ -126,6 +126,8 @@ declare_features! ( (accepted, default_type_params, "1.0.0", None, None), /// Allows `#[deprecated]` attribute. (accepted, deprecated, "1.9.0", Some(29935), None), + /// Allows `#[derive(Default)]` and `#[default]` on enums. + (accepted, derive_default_enum, "1.62.0", Some(86985), None), /// Allows the use of destructuring assignments. (accepted, destructuring_assignment, "1.59.0", Some(71126), None), /// Allows `#[doc(alias = "...")]`. diff --git a/compiler/rustc_feature/src/active.rs b/compiler/rustc_feature/src/active.rs index 28466315c86..81863162df3 100644 --- a/compiler/rustc_feature/src/active.rs +++ b/compiler/rustc_feature/src/active.rs @@ -368,8 +368,6 @@ declare_features! ( (active, deprecated_safe, "1.61.0", Some(94978), None), /// Allows having using `suggestion` in the `#[deprecated]` attribute. (active, deprecated_suggestion, "1.61.0", Some(94785), None), - /// Allows `#[derive(Default)]` and `#[default]` on enums. - (active, derive_default_enum, "1.56.0", Some(86985), None), /// Tells rustdoc to automatically generate `#[doc(cfg(...))]`. (active, doc_auto_cfg, "1.58.0", Some(43781), None), /// Allows `#[doc(cfg(...))]`. diff --git a/compiler/rustc_feature/src/lib.rs b/compiler/rustc_feature/src/lib.rs index bfc537cfae2..940c4ecdcc2 100644 --- a/compiler/rustc_feature/src/lib.rs +++ b/compiler/rustc_feature/src/lib.rs @@ -11,7 +11,7 @@ //! even if it is stabilized or removed, *do not remove it*. Instead, move the //! symbol to the `accepted` or `removed` modules respectively. -#![feature(derive_default_enum)] +#![cfg_attr(bootstrap, feature(derive_default_enum))] #![feature(once_cell)] mod accepted; diff --git a/compiler/rustc_infer/src/lib.rs b/compiler/rustc_infer/src/lib.rs index 08e005364ce..e859bcaec12 100644 --- a/compiler/rustc_infer/src/lib.rs +++ b/compiler/rustc_infer/src/lib.rs @@ -17,7 +17,7 @@ #![feature(bool_to_option)] #![feature(box_patterns)] #![feature(control_flow_enum)] -#![feature(derive_default_enum)] +#![cfg_attr(bootstrap, feature(derive_default_enum))] #![feature(extend_one)] #![feature(label_break_value)] #![feature(let_chains)] diff --git a/compiler/rustc_middle/src/lib.rs b/compiler/rustc_middle/src/lib.rs index fa2dad5ce25..cffcd6699b6 100644 --- a/compiler/rustc_middle/src/lib.rs +++ b/compiler/rustc_middle/src/lib.rs @@ -30,7 +30,7 @@ #![feature(bool_to_option)] #![feature(box_patterns)] #![feature(core_intrinsics)] -#![feature(derive_default_enum)] +#![cfg_attr(bootstrap, feature(derive_default_enum))] #![feature(discriminant_kind)] #![feature(exhaustive_patterns)] #![feature(get_mut_unchecked)] diff --git a/compiler/rustc_session/src/lib.rs b/compiler/rustc_session/src/lib.rs index 3151b025fff..054b18b6b63 100644 --- a/compiler/rustc_session/src/lib.rs +++ b/compiler/rustc_session/src/lib.rs @@ -1,7 +1,7 @@ #![feature(crate_visibility_modifier)] -#![feature(derive_default_enum)] #![feature(if_let_guard)] #![feature(let_chains)] +#![cfg_attr(bootstrap, feature(derive_default_enum))] #![feature(let_else)] #![feature(min_specialization)] #![feature(never_type)] diff --git a/compiler/rustc_trait_selection/src/lib.rs b/compiler/rustc_trait_selection/src/lib.rs index 7523b844101..2ae7f34a91e 100644 --- a/compiler/rustc_trait_selection/src/lib.rs +++ b/compiler/rustc_trait_selection/src/lib.rs @@ -16,7 +16,7 @@ #![feature(box_patterns)] #![feature(control_flow_enum)] #![feature(crate_visibility_modifier)] -#![feature(derive_default_enum)] +#![cfg_attr(bootstrap, feature(derive_default_enum))] #![feature(drain_filter)] #![feature(hash_drain_filter)] #![feature(label_break_value)] diff --git a/library/core/src/lib.rs b/library/core/src/lib.rs index 660f6d92fe1..dc6bec246b9 100644 --- a/library/core/src/lib.rs +++ b/library/core/src/lib.rs @@ -167,7 +167,7 @@ #![feature(const_precise_live_drops)] #![feature(const_refs_to_cell)] #![feature(decl_macro)] -#![feature(derive_default_enum)] +#![cfg_attr(bootstrap, feature(derive_default_enum))] #![feature(deprecated_suggestion)] #![feature(doc_cfg)] #![feature(doc_notable_trait)] diff --git a/src/test/ui/deriving/deriving-default-enum.rs b/src/test/ui/deriving/deriving-default-enum.rs index 931ff1a5847..d1a81c72c2f 100644 --- a/src/test/ui/deriving/deriving-default-enum.rs +++ b/src/test/ui/deriving/deriving-default-enum.rs @@ -1,7 +1,5 @@ // run-pass -#![feature(derive_default_enum)] - // nb: does not impl Default #[derive(Debug, PartialEq)] struct NotDefault; diff --git a/src/test/ui/deriving/deriving-with-helper.rs b/src/test/ui/deriving/deriving-with-helper.rs index d8f0b27a2e5..1c30b0b6fba 100644 --- a/src/test/ui/deriving/deriving-with-helper.rs +++ b/src/test/ui/deriving/deriving-with-helper.rs @@ -5,7 +5,6 @@ #![feature(lang_items)] #![feature(no_core)] #![feature(rustc_attrs)] -#![feature(derive_default_enum)] #![no_core] diff --git a/src/test/ui/feature-gates/feature-gate-derive_default_enum.rs b/src/test/ui/feature-gates/feature-gate-derive_default_enum.rs deleted file mode 100644 index 05a5d4e1422..00000000000 --- a/src/test/ui/feature-gates/feature-gate-derive_default_enum.rs +++ /dev/null @@ -1,7 +0,0 @@ -#[derive(Default)] //~ ERROR deriving `Default` on enums is experimental -enum Foo { - #[default] - Alpha, -} - -fn main() {} diff --git a/src/test/ui/feature-gates/feature-gate-derive_default_enum.stderr b/src/test/ui/feature-gates/feature-gate-derive_default_enum.stderr deleted file mode 100644 index 58dd4d508a7..00000000000 --- a/src/test/ui/feature-gates/feature-gate-derive_default_enum.stderr +++ /dev/null @@ -1,13 +0,0 @@ -error[E0658]: deriving `Default` on enums is experimental - --> $DIR/feature-gate-derive_default_enum.rs:1:10 - | -LL | #[derive(Default)] - | ^^^^^^^ - | - = note: see issue #86985 for more information - = help: add `#![feature(derive_default_enum)]` to the crate attributes to enable - = note: this error originates in the derive macro `Default` (in Nightly builds, run with -Z macro-backtrace for more info) - -error: aborting due to previous error - -For more information about this error, try `rustc --explain E0658`. diff --git a/src/test/ui/macros/macros-nonfatal-errors.rs b/src/test/ui/macros/macros-nonfatal-errors.rs index 98f64aa6f80..e7a01f105de 100644 --- a/src/test/ui/macros/macros-nonfatal-errors.rs +++ b/src/test/ui/macros/macros-nonfatal-errors.rs @@ -5,7 +5,6 @@ #![feature(trace_macros, concat_idents)] #![feature(stmt_expr_attributes, arbitrary_enum_discriminant)] -#![feature(derive_default_enum)] use std::arch::asm; diff --git a/src/test/ui/macros/macros-nonfatal-errors.stderr b/src/test/ui/macros/macros-nonfatal-errors.stderr index 79e8db9c1d4..b3c6d07f967 100644 --- a/src/test/ui/macros/macros-nonfatal-errors.stderr +++ b/src/test/ui/macros/macros-nonfatal-errors.stderr @@ -1,41 +1,41 @@ error: the `#[default]` attribute may only be used on unit enum variants - --> $DIR/macros-nonfatal-errors.rs:14:5 + --> $DIR/macros-nonfatal-errors.rs:13:5 | LL | #[default] | ^^^^^^^^^^ error: the `#[default]` attribute may only be used on unit enum variants - --> $DIR/macros-nonfatal-errors.rs:19:36 + --> $DIR/macros-nonfatal-errors.rs:18:36 | LL | struct DefaultInnerAttrTupleStruct(#[default] ()); | ^^^^^^^^^^ error: the `#[default]` attribute may only be used on unit enum variants - --> $DIR/macros-nonfatal-errors.rs:23:1 + --> $DIR/macros-nonfatal-errors.rs:22:1 | LL | #[default] | ^^^^^^^^^^ error: the `#[default]` attribute may only be used on unit enum variants - --> $DIR/macros-nonfatal-errors.rs:27:1 + --> $DIR/macros-nonfatal-errors.rs:26:1 | LL | #[default] | ^^^^^^^^^^ error: the `#[default]` attribute may only be used on unit enum variants - --> $DIR/macros-nonfatal-errors.rs:37:11 + --> $DIR/macros-nonfatal-errors.rs:36:11 | LL | Foo = #[default] 0, | ^^^^^^^^^^ error: the `#[default]` attribute may only be used on unit enum variants - --> $DIR/macros-nonfatal-errors.rs:38:14 + --> $DIR/macros-nonfatal-errors.rs:37:14 | LL | Bar([u8; #[default] 1]), | ^^^^^^^^^^ error: no default declared - --> $DIR/macros-nonfatal-errors.rs:43:10 + --> $DIR/macros-nonfatal-errors.rs:42:10 | LL | #[derive(Default)] | ^^^^^^^ @@ -44,7 +44,7 @@ LL | #[derive(Default)] = note: this error originates in the derive macro `Default` (in Nightly builds, run with -Z macro-backtrace for more info) error: multiple declared defaults - --> $DIR/macros-nonfatal-errors.rs:49:10 + --> $DIR/macros-nonfatal-errors.rs:48:10 | LL | #[derive(Default)] | ^^^^^^^ @@ -62,7 +62,7 @@ LL | Baz, = note: this error originates in the derive macro `Default` (in Nightly builds, run with -Z macro-backtrace for more info) error: `#[default]` attribute does not accept a value - --> $DIR/macros-nonfatal-errors.rs:61:5 + --> $DIR/macros-nonfatal-errors.rs:60:5 | LL | #[default = 1] | ^^^^^^^^^^^^^^ @@ -70,7 +70,7 @@ LL | #[default = 1] = help: try using `#[default]` error: multiple `#[default]` attributes - --> $DIR/macros-nonfatal-errors.rs:69:5 + --> $DIR/macros-nonfatal-errors.rs:68:5 | LL | #[default] | ---------- `#[default]` used here @@ -81,13 +81,13 @@ LL | Foo, | = note: only one `#[default]` attribute is needed help: try removing this - --> $DIR/macros-nonfatal-errors.rs:68:5 + --> $DIR/macros-nonfatal-errors.rs:67:5 | LL | #[default] | ^^^^^^^^^^ error: multiple `#[default]` attributes - --> $DIR/macros-nonfatal-errors.rs:79:5 + --> $DIR/macros-nonfatal-errors.rs:78:5 | LL | #[default] | ---------- `#[default]` used here @@ -99,7 +99,7 @@ LL | Foo, | = note: only one `#[default]` attribute is needed help: try removing these - --> $DIR/macros-nonfatal-errors.rs:76:5 + --> $DIR/macros-nonfatal-errors.rs:75:5 | LL | #[default] | ^^^^^^^^^^ @@ -109,7 +109,7 @@ LL | #[default] | ^^^^^^^^^^ error: the `#[default]` attribute may only be used on unit enum variants - --> $DIR/macros-nonfatal-errors.rs:86:5 + --> $DIR/macros-nonfatal-errors.rs:85:5 | LL | Foo {}, | ^^^ @@ -117,7 +117,7 @@ LL | Foo {}, = help: consider a manual implementation of `Default` error: default variant must be exhaustive - --> $DIR/macros-nonfatal-errors.rs:94:5 + --> $DIR/macros-nonfatal-errors.rs:93:5 | LL | #[non_exhaustive] | ----------------- declared `#[non_exhaustive]` here @@ -127,37 +127,37 @@ LL | Foo, = help: consider a manual implementation of `Default` error: asm template must be a string literal - --> $DIR/macros-nonfatal-errors.rs:99:10 + --> $DIR/macros-nonfatal-errors.rs:98:10 | LL | asm!(invalid); | ^^^^^^^ error: concat_idents! requires ident args - --> $DIR/macros-nonfatal-errors.rs:102:5 + --> $DIR/macros-nonfatal-errors.rs:101:5 | LL | concat_idents!("not", "idents"); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ error: argument must be a string literal - --> $DIR/macros-nonfatal-errors.rs:104:17 + --> $DIR/macros-nonfatal-errors.rs:103:17 | LL | option_env!(invalid); | ^^^^^^^ error: expected string literal - --> $DIR/macros-nonfatal-errors.rs:105:10 + --> $DIR/macros-nonfatal-errors.rs:104:10 | LL | env!(invalid); | ^^^^^^^ error: expected string literal - --> $DIR/macros-nonfatal-errors.rs:106:10 + --> $DIR/macros-nonfatal-errors.rs:105:10 | LL | env!(foo, abr, baz); | ^^^ error: environment variable `RUST_HOPEFULLY_THIS_DOESNT_EXIST` not defined - --> $DIR/macros-nonfatal-errors.rs:107:5 + --> $DIR/macros-nonfatal-errors.rs:106:5 | LL | env!("RUST_HOPEFULLY_THIS_DOESNT_EXIST"); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -165,7 +165,7 @@ LL | env!("RUST_HOPEFULLY_THIS_DOESNT_EXIST"); = note: this error originates in the macro `env` (in Nightly builds, run with -Z macro-backtrace for more info) error: format argument must be a string literal - --> $DIR/macros-nonfatal-errors.rs:109:13 + --> $DIR/macros-nonfatal-errors.rs:108:13 | LL | format!(invalid); | ^^^^^^^ @@ -176,19 +176,19 @@ LL | format!("{}", invalid); | +++++ error: argument must be a string literal - --> $DIR/macros-nonfatal-errors.rs:111:14 + --> $DIR/macros-nonfatal-errors.rs:110:14 | LL | include!(invalid); | ^^^^^^^ error: argument must be a string literal - --> $DIR/macros-nonfatal-errors.rs:113:18 + --> $DIR/macros-nonfatal-errors.rs:112:18 | LL | include_str!(invalid); | ^^^^^^^ error: couldn't read $DIR/i'd be quite surprised if a file with this name existed: $FILE_NOT_FOUND_MSG (os error 2) - --> $DIR/macros-nonfatal-errors.rs:114:5 + --> $DIR/macros-nonfatal-errors.rs:113:5 | LL | include_str!("i'd be quite surprised if a file with this name existed"); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -196,13 +196,13 @@ LL | include_str!("i'd be quite surprised if a file with this name existed") = note: this error originates in the macro `include_str` (in Nightly builds, run with -Z macro-backtrace for more info) error: argument must be a string literal - --> $DIR/macros-nonfatal-errors.rs:115:20 + --> $DIR/macros-nonfatal-errors.rs:114:20 | LL | include_bytes!(invalid); | ^^^^^^^ error: couldn't read $DIR/i'd be quite surprised if a file with this name existed: $FILE_NOT_FOUND_MSG (os error 2) - --> $DIR/macros-nonfatal-errors.rs:116:5 + --> $DIR/macros-nonfatal-errors.rs:115:5 | LL | include_bytes!("i'd be quite surprised if a file with this name existed"); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -210,13 +210,13 @@ LL | include_bytes!("i'd be quite surprised if a file with this name existed = note: this error originates in the macro `include_bytes` (in Nightly builds, run with -Z macro-backtrace for more info) error: trace_macros! accepts only `true` or `false` - --> $DIR/macros-nonfatal-errors.rs:118:5 + --> $DIR/macros-nonfatal-errors.rs:117:5 | LL | trace_macros!(invalid); | ^^^^^^^^^^^^^^^^^^^^^^ error: cannot find macro `llvm_asm` in this scope - --> $DIR/macros-nonfatal-errors.rs:100:5 + --> $DIR/macros-nonfatal-errors.rs:99:5 | LL | llvm_asm!(invalid); | ^^^^^^^^ From a3dd654ae9f9002d3ff47e45a9a9b6afcb484d2f Mon Sep 17 00:00:00 2001 From: Jacob Pratt Date: Tue, 8 Mar 2022 15:44:52 -0500 Subject: [PATCH 2/2] Add documentation --- library/core/src/default.rs | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/library/core/src/default.rs b/library/core/src/default.rs index fb862f7df94..1ce00828bf3 100644 --- a/library/core/src/default.rs +++ b/library/core/src/default.rs @@ -52,6 +52,23 @@ /// This trait can be used with `#[derive]` if all of the type's fields implement /// `Default`. When `derive`d, it will use the default value for each field's type. /// +/// ### `enum`s +/// +/// When using `#[derive(Default)]` on an `enum`, you need to choose which unit variant will be +/// default. You do this by placing the `#[default]` attribute on the variant. +/// +/// ``` +/// #[derive(Default)] +/// enum Kind { +/// #[default] +/// A, +/// B, +/// C, +/// } +/// ``` +/// +/// You cannot use the `#[default]` attribute on non-unit or non-exhaustive variants. +/// /// ## How can I implement `Default`? /// /// Provide an implementation for the `default()` method that returns the value of