From 92fbfae16b868be626465d005222366ad4b31960 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Le=C3=B3n=20Orell=20Valerian=20Liehr?= Date: Sat, 28 Mar 2026 19:20:21 +0100 Subject: [PATCH] Emit pre-expansion feature gate warning for item modifier `default` --- compiler/rustc_ast_passes/src/feature_gate.rs | 15 ++++- compiler/rustc_parse/src/parser/item.rs | 11 +++- tests/ui/macros/stringify.rs | 3 +- .../trait-item-with-defaultness-pass.rs | 1 + .../feature-gate-specialization.rs | 21 +++++++ .../feature-gate-specialization.stderr | 45 ++++++++++++++ ...feature-gate-specialization.default.stderr | 62 +++++++++++++++++++ ...oft-feature-gate-specialization.min.stderr | 38 ++++++++++++ .../soft-feature-gate-specialization.rs | 44 +++++++++++++ .../specialization-feature-gate-default.rs | 13 ---- ...specialization-feature-gate-default.stderr | 13 ---- tests/ui/track-diagnostics/track6.rs | 2 +- tests/ui/track-diagnostics/track6.stderr | 2 +- 13 files changed, 238 insertions(+), 32 deletions(-) create mode 100644 tests/ui/specialization/feature-gate-specialization.rs create mode 100644 tests/ui/specialization/feature-gate-specialization.stderr create mode 100644 tests/ui/specialization/soft-feature-gate-specialization.default.stderr create mode 100644 tests/ui/specialization/soft-feature-gate-specialization.min.stderr create mode 100644 tests/ui/specialization/soft-feature-gate-specialization.rs delete mode 100644 tests/ui/specialization/specialization-feature-gate-default.rs delete mode 100644 tests/ui/specialization/specialization-feature-gate-default.stderr diff --git a/compiler/rustc_ast_passes/src/feature_gate.rs b/compiler/rustc_ast_passes/src/feature_gate.rs index ae046c61c276..1b615b611258 100644 --- a/compiler/rustc_ast_passes/src/feature_gate.rs +++ b/compiler/rustc_ast_passes/src/feature_gate.rs @@ -224,7 +224,7 @@ fn visit_item(&mut self, i: &'a ast::Item) { } if let ast::Defaultness::Default(_) = of_trait.defaultness { - gate!(self, specialization, i.span, "specialization is unstable"); + gate!(self, specialization, i.span, "specialization is experimental"); } } @@ -450,7 +450,7 @@ fn visit_assoc_item(&mut self, i: &'a ast::AssocItem, ctxt: AssocCtxt) { self.features.specialization() || (is_fn && self.features.min_specialization()), sym::specialization, i.span, - "specialization is unstable" + "specialization is experimental" ); } visit::walk_assoc_item(self, i, ctxt) @@ -615,10 +615,21 @@ macro_rules! soft_gate_all_legacy_dont_use { soft_gate_all_legacy_dont_use!(box_patterns, "box pattern syntax is experimental"); soft_gate_all_legacy_dont_use!(decl_macro, "`macro` is experimental"); soft_gate_all_legacy_dont_use!(negative_impls, "negative impls are experimental"); + soft_gate_all_legacy_dont_use!(specialization, "specialization is experimental"); soft_gate_all_legacy_dont_use!(trait_alias, "trait aliases are experimental"); soft_gate_all_legacy_dont_use!(try_blocks, "`try` blocks are unstable"); // tidy-alphabetical-end + for &span in spans.get(&sym::min_specialization).into_iter().flatten() { + if !visitor.features.specialization() + && !visitor.features.min_specialization() + && !span.allows_unstable(sym::specialization) + && !span.allows_unstable(sym::min_specialization) + { + feature_warn(visitor.sess, sym::specialization, span, "specialization is experimental"); + } + } + // ----------------------------------------------------------------------------- visit::walk_crate(&mut visitor, krate); diff --git a/compiler/rustc_parse/src/parser/item.rs b/compiler/rustc_parse/src/parser/item.rs index 823d5957949c..79b79db6ccc0 100644 --- a/compiler/rustc_parse/src/parser/item.rs +++ b/compiler/rustc_parse/src/parser/item.rs @@ -248,10 +248,18 @@ fn parse_item_kind( self.parse_use_item()? } else if self.check_fn_front_matter(check_pub, case) { // FUNCTION ITEM + let defaultness = def_(); + if let Defaultness::Default(span) = defaultness { + // Default functions should only require feature `min_specialization`. We remove the + // `specialization` tag again as such spans *require* feature `specialization` to be + // enabled. In a later stage, we make `specialization` imply `min_specialization`. + self.psess.gated_spans.gate(sym::min_specialization, span); + self.psess.gated_spans.ungate_last(sym::specialization, span); + } let (ident, sig, generics, contract, body) = self.parse_fn(attrs, fn_parse_mode, lo, vis, case)?; ItemKind::Fn(Box::new(Fn { - defaultness: def_(), + defaultness, ident, sig, generics, @@ -1016,6 +1024,7 @@ fn parse_defaultness(&mut self) -> Defaultness { if self.check_keyword(exp!(Default)) && self.look_ahead(1, |t| t.is_non_raw_ident_where(|i| i.name != kw::As)) { + self.psess.gated_spans.gate(sym::specialization, self.token.span); self.bump(); // `default` Defaultness::Default(self.prev_token_uninterpolated_span()) } else if self.eat_keyword(exp!(Final)) { diff --git a/tests/ui/macros/stringify.rs b/tests/ui/macros/stringify.rs index af2ba7a809ad..46f50593c4e9 100644 --- a/tests/ui/macros/stringify.rs +++ b/tests/ui/macros/stringify.rs @@ -9,12 +9,13 @@ #![feature(const_trait_impl)] #![feature(coroutines)] #![feature(decl_macro)] +#![feature(macro_guard_matcher)] #![feature(more_qualified_paths)] #![feature(never_patterns)] +#![feature(specialization)] #![feature(trait_alias)] #![feature(try_blocks)] #![feature(yeet_expr)] -#![feature(macro_guard_matcher)] #![deny(unused_macros)] // These macros force the use of AST pretty-printing by converting the input to diff --git a/tests/ui/parser/trait-item-with-defaultness-pass.rs b/tests/ui/parser/trait-item-with-defaultness-pass.rs index 164d0b13b539..e8452fcbd5f9 100644 --- a/tests/ui/parser/trait-item-with-defaultness-pass.rs +++ b/tests/ui/parser/trait-item-with-defaultness-pass.rs @@ -1,4 +1,5 @@ //@ check-pass +#![feature(specialization)] fn main() {} diff --git a/tests/ui/specialization/feature-gate-specialization.rs b/tests/ui/specialization/feature-gate-specialization.rs new file mode 100644 index 000000000000..82e467ad98d3 --- /dev/null +++ b/tests/ui/specialization/feature-gate-specialization.rs @@ -0,0 +1,21 @@ +trait Trait { + type Ty; + const CT: (); + fn fn_(&self); +} + +impl Trait for T { + default type Ty = (); //~ ERROR specialization is experimental + default const CT: () = (); //~ ERROR specialization is experimental + default fn fn_(&self) {} //~ ERROR specialization is experimental +} + +trait OtherTrait { + fn fn_(); +} + +default impl OtherTrait for T { //~ ERROR specialization is experimental + fn fn_() {} +} + +fn main() {} diff --git a/tests/ui/specialization/feature-gate-specialization.stderr b/tests/ui/specialization/feature-gate-specialization.stderr new file mode 100644 index 000000000000..2efc0faa7c23 --- /dev/null +++ b/tests/ui/specialization/feature-gate-specialization.stderr @@ -0,0 +1,45 @@ +error[E0658]: specialization is experimental + --> $DIR/feature-gate-specialization.rs:8:5 + | +LL | default type Ty = (); + | ^^^^^^^^^^^^^^^^^^^^^ + | + = note: see issue #31844 for more information + = help: add `#![feature(specialization)]` to the crate attributes to enable + = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date + +error[E0658]: specialization is experimental + --> $DIR/feature-gate-specialization.rs:9:5 + | +LL | default const CT: () = (); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = note: see issue #31844 for more information + = help: add `#![feature(specialization)]` to the crate attributes to enable + = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date + +error[E0658]: specialization is experimental + --> $DIR/feature-gate-specialization.rs:10:5 + | +LL | default fn fn_(&self) {} + | ^^^^^^^^^^^^^^^^^^^^^^^^ + | + = note: see issue #31844 for more information + = help: add `#![feature(specialization)]` to the crate attributes to enable + = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date + +error[E0658]: specialization is experimental + --> $DIR/feature-gate-specialization.rs:17:1 + | +LL | / default impl OtherTrait for T { +LL | | fn fn_() {} +LL | | } + | |_^ + | + = note: see issue #31844 for more information + = help: add `#![feature(specialization)]` to the crate attributes to enable + = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date + +error: aborting due to 4 previous errors + +For more information about this error, try `rustc --explain E0658`. diff --git a/tests/ui/specialization/soft-feature-gate-specialization.default.stderr b/tests/ui/specialization/soft-feature-gate-specialization.default.stderr new file mode 100644 index 000000000000..f5961090947e --- /dev/null +++ b/tests/ui/specialization/soft-feature-gate-specialization.default.stderr @@ -0,0 +1,62 @@ +warning: specialization is experimental + --> $DIR/soft-feature-gate-specialization.rs:21:5 + | +LL | default type Ty = (); + | ^^^^^^^ + | + = note: see issue #31844 for more information + = help: add `#![feature(specialization)]` to the crate attributes to enable + = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date + = warning: unstable syntax can change at any point in the future, causing a hard error! + = note: for more information, see issue #65860 + +warning: specialization is experimental + --> $DIR/soft-feature-gate-specialization.rs:24:5 + | +LL | default const CT: () = (); + | ^^^^^^^ + | + = note: see issue #31844 for more information + = help: add `#![feature(specialization)]` to the crate attributes to enable + = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date + = warning: unstable syntax can change at any point in the future, causing a hard error! + = note: for more information, see issue #65860 + +warning: specialization is experimental + --> $DIR/soft-feature-gate-specialization.rs:40:1 + | +LL | default impl Trait for () {} + | ^^^^^^^ + | + = note: see issue #31844 for more information + = help: add `#![feature(specialization)]` to the crate attributes to enable + = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date + = warning: unstable syntax can change at any point in the future, causing a hard error! + = note: for more information, see issue #65860 + +warning: specialization is experimental + --> $DIR/soft-feature-gate-specialization.rs:27:5 + | +LL | default fn fn_(); + | ^^^^^^^ + | + = note: see issue #31844 for more information + = help: add `#![feature(specialization)]` to the crate attributes to enable + = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date + = warning: unstable syntax can change at any point in the future, causing a hard error! + = note: for more information, see issue #65860 + +warning: specialization is experimental + --> $DIR/soft-feature-gate-specialization.rs:35:1 + | +LL | default fn fn_() {} + | ^^^^^^^ + | + = note: see issue #31844 for more information + = help: add `#![feature(specialization)]` to the crate attributes to enable + = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date + = warning: unstable syntax can change at any point in the future, causing a hard error! + = note: for more information, see issue #65860 + +warning: 5 warnings emitted + diff --git a/tests/ui/specialization/soft-feature-gate-specialization.min.stderr b/tests/ui/specialization/soft-feature-gate-specialization.min.stderr new file mode 100644 index 000000000000..aa4ce0cc58be --- /dev/null +++ b/tests/ui/specialization/soft-feature-gate-specialization.min.stderr @@ -0,0 +1,38 @@ +warning: specialization is experimental + --> $DIR/soft-feature-gate-specialization.rs:21:5 + | +LL | default type Ty = (); + | ^^^^^^^ + | + = note: see issue #31844 for more information + = help: add `#![feature(specialization)]` to the crate attributes to enable + = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date + = warning: unstable syntax can change at any point in the future, causing a hard error! + = note: for more information, see issue #65860 + +warning: specialization is experimental + --> $DIR/soft-feature-gate-specialization.rs:24:5 + | +LL | default const CT: () = (); + | ^^^^^^^ + | + = note: see issue #31844 for more information + = help: add `#![feature(specialization)]` to the crate attributes to enable + = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date + = warning: unstable syntax can change at any point in the future, causing a hard error! + = note: for more information, see issue #65860 + +warning: specialization is experimental + --> $DIR/soft-feature-gate-specialization.rs:40:1 + | +LL | default impl Trait for () {} + | ^^^^^^^ + | + = note: see issue #31844 for more information + = help: add `#![feature(specialization)]` to the crate attributes to enable + = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date + = warning: unstable syntax can change at any point in the future, causing a hard error! + = note: for more information, see issue #65860 + +warning: 3 warnings emitted + diff --git a/tests/ui/specialization/soft-feature-gate-specialization.rs b/tests/ui/specialization/soft-feature-gate-specialization.rs new file mode 100644 index 000000000000..e671bc20a1f3 --- /dev/null +++ b/tests/ui/specialization/soft-feature-gate-specialization.rs @@ -0,0 +1,44 @@ +// For historical reasons, item modifier `default` doesn't have a proper pre-expansion feature gate. +// We're now at least issuing a *warning* for those that only exist before macro expansion. +// FIXME(#154045): Turn their post-expansion feature gate into a proper pre-expansion one. +// As part of this, move these test cases into `feature-gate-specialization.rs`. +// +// Moreover, `specialization` implies `min_specialization` similar to the post-expansion gate. +// +// However, while we only gate `default` *associated* functions only behind `min_specialization` OR +// `specialization` in the post-expansion case, in the pre-expansion case we gate all kinds of +// functions (free, assoc, foreign) behind `min_specialization` OR `specialization` if marked with +// `default` for simplicity of implementation. Ultimately it doesn't matter since we later reject +// `default` on anything other than impls & impl assoc items during semantic analysis. +// +//@ revisions: default min full +//@ check-pass +#![cfg_attr(min, feature(min_specialization))] +#![cfg_attr(full, feature(specialization))] + +#[cfg(false)] +impl Trait for () { + default type Ty = (); + //[default,min]~^ WARN specialization is experimental + //[default,min]~| WARN unstable syntax can change at any point in the future + default const CT: () = (); + //[default,min]~^ WARN specialization is experimental + //[default,min]~| WARN unstable syntax can change at any point in the future + default fn fn_(); + //[default]~^ WARN specialization is experimental + //[default]~| WARN unstable syntax can change at any point in the future +} + +// While free ty/ct/fn items marked `default` are +// semantically malformed we still need to gate the keyword! +#[cfg(false)] +default fn fn_() {} +//[default]~^ WARN specialization is experimental +//[default]~| WARN unstable syntax can change at any point in the future + +#[cfg(false)] +default impl Trait for () {} +//[default,min]~^ WARN specialization is experimental +//[default,min]~| WARN unstable syntax can change at any point in the future + +fn main() {} diff --git a/tests/ui/specialization/specialization-feature-gate-default.rs b/tests/ui/specialization/specialization-feature-gate-default.rs deleted file mode 100644 index 8bad3ac0a1fb..000000000000 --- a/tests/ui/specialization/specialization-feature-gate-default.rs +++ /dev/null @@ -1,13 +0,0 @@ -// Check that specialization must be ungated to use the `default` keyword - -// gate-test-specialization - -trait Foo { - fn foo(&self); -} - -impl Foo for T { - default fn foo(&self) {} //~ ERROR specialization is unstable -} - -fn main() {} diff --git a/tests/ui/specialization/specialization-feature-gate-default.stderr b/tests/ui/specialization/specialization-feature-gate-default.stderr deleted file mode 100644 index 3e651b6ee4f3..000000000000 --- a/tests/ui/specialization/specialization-feature-gate-default.stderr +++ /dev/null @@ -1,13 +0,0 @@ -error[E0658]: specialization is unstable - --> $DIR/specialization-feature-gate-default.rs:10:5 - | -LL | default fn foo(&self) {} - | ^^^^^^^^^^^^^^^^^^^^^^^^ - | - = note: see issue #31844 for more information - = help: add `#![feature(specialization)]` to the crate attributes to enable - = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date - -error: aborting due to 1 previous error - -For more information about this error, try `rustc --explain E0658`. diff --git a/tests/ui/track-diagnostics/track6.rs b/tests/ui/track-diagnostics/track6.rs index aa75c5691e5f..38d34f46270a 100644 --- a/tests/ui/track-diagnostics/track6.rs +++ b/tests/ui/track-diagnostics/track6.rs @@ -12,7 +12,7 @@ pub trait Foo { impl Foo for T { default fn bar() {} - //~^ ERROR specialization is unstable + //~^ ERROR specialization is experimental //~| NOTE created at } diff --git a/tests/ui/track-diagnostics/track6.stderr b/tests/ui/track-diagnostics/track6.stderr index a61f7855e323..30d518a69cad 100644 --- a/tests/ui/track-diagnostics/track6.stderr +++ b/tests/ui/track-diagnostics/track6.stderr @@ -1,4 +1,4 @@ -error[E0658]: specialization is unstable +error[E0658]: specialization is experimental --> $DIR/track6.rs:LL:CC | LL | default fn bar() {}