From 66f3ab90a14254d70c96acb0332fe403964025ce Mon Sep 17 00:00:00 2001 From: Gary Guo Date: Fri, 9 Dec 2022 02:27:03 +0000 Subject: [PATCH] Reintroduce multiple_supertrait_upcastable lint --- .../locales/en-US/lint.ftl | 2 + compiler/rustc_feature/src/active.rs | 2 + compiler/rustc_lint/src/lib.rs | 3 + compiler/rustc_lint/src/lints.rs | 7 +++ .../src/multiple_supertrait_upcastable.rs | 60 +++++++++++++++++++ compiler/rustc_span/src/symbol.rs | 1 + library/alloc/src/lib.rs | 2 + library/core/src/error.rs | 1 + library/core/src/lib.rs | 2 + ...ure-gate-multiple_supertrait_upcastable.rs | 12 ++++ ...gate-multiple_supertrait_upcastable.stderr | 57 ++++++++++++++++++ .../multiple_supertrait_upcastable.rs | 10 ++++ .../multiple_supertrait_upcastable.stderr | 14 +++++ 13 files changed, 173 insertions(+) create mode 100644 compiler/rustc_lint/src/multiple_supertrait_upcastable.rs create mode 100644 tests/ui/feature-gates/feature-gate-multiple_supertrait_upcastable.rs create mode 100644 tests/ui/feature-gates/feature-gate-multiple_supertrait_upcastable.stderr create mode 100644 tests/ui/traits/trait-upcasting/multiple_supertrait_upcastable.rs create mode 100644 tests/ui/traits/trait-upcasting/multiple_supertrait_upcastable.stderr diff --git a/compiler/rustc_error_messages/locales/en-US/lint.ftl b/compiler/rustc_error_messages/locales/en-US/lint.ftl index d63ff77d8e2..dca678dff7a 100644 --- a/compiler/rustc_error_messages/locales/en-US/lint.ftl +++ b/compiler/rustc_error_messages/locales/en-US/lint.ftl @@ -100,6 +100,8 @@ lint_cstring_ptr = getting the inner pointer of a temporary `CString` .note = pointers do not have a lifetime; when calling `as_ptr` the `CString` will be deallocated at the end of the statement because nothing is referencing it as far as the type system is concerned .help = for more information, see https://doc.rust-lang.org/reference/destructors.html +lint_multple_supertrait_upcastable = `{$ident}` is object-safe and has multiple supertraits + lint_identifier_non_ascii_char = identifier contains non-ASCII characters lint_identifier_uncommon_codepoints = identifier contains uncommon Unicode codepoints diff --git a/compiler/rustc_feature/src/active.rs b/compiler/rustc_feature/src/active.rs index 196c31302a0..af9c40a3ba5 100644 --- a/compiler/rustc_feature/src/active.rs +++ b/compiler/rustc_feature/src/active.rs @@ -160,6 +160,8 @@ declare_features! ( (active, intrinsics, "1.0.0", None, None), /// Allows using `#[lang = ".."]` attribute for linking items to special compiler logic. (active, lang_items, "1.0.0", None, None), + /// Allows the `multiple_supertrait_upcastable` lint. + (active, multiple_supertrait_upcastable, "CURRENT_RUSTC_VERSION", None, None), /// Allows using `#[omit_gdb_pretty_printer_section]`. (active, omit_gdb_pretty_printer_section, "1.5.0", None, None), /// Allows using `#[prelude_import]` on glob `use` items. diff --git a/compiler/rustc_lint/src/lib.rs b/compiler/rustc_lint/src/lib.rs index d6be4da0328..ba15dbd86cf 100644 --- a/compiler/rustc_lint/src/lib.rs +++ b/compiler/rustc_lint/src/lib.rs @@ -64,6 +64,7 @@ mod let_underscore; mod levels; mod lints; mod methods; +mod multiple_supertrait_upcastable; mod non_ascii_idents; mod non_fmt_panic; mod nonstandard_style; @@ -98,6 +99,7 @@ use hidden_unicode_codepoints::*; use internal::*; use let_underscore::*; use methods::*; +use multiple_supertrait_upcastable::*; use non_ascii_idents::*; use non_fmt_panic::NonPanicFmt; use nonstandard_style::*; @@ -232,6 +234,7 @@ late_lint_methods!( InvalidAtomicOrdering: InvalidAtomicOrdering, NamedAsmLabels: NamedAsmLabels, OpaqueHiddenInferredBound: OpaqueHiddenInferredBound, + MultipleSupertraitUpcastable: MultipleSupertraitUpcastable, ] ] ); diff --git a/compiler/rustc_lint/src/lints.rs b/compiler/rustc_lint/src/lints.rs index c997d8945d1..0c1019545f3 100644 --- a/compiler/rustc_lint/src/lints.rs +++ b/compiler/rustc_lint/src/lints.rs @@ -917,6 +917,13 @@ pub struct CStringPtr { pub unwrap: Span, } +// multiple_supertrait_upcastable.rs +#[derive(LintDiagnostic)] +#[diag(lint_multple_supertrait_upcastable)] +pub struct MultipleSupertraitUpcastable { + pub ident: Ident, +} + // non_ascii_idents.rs #[derive(LintDiagnostic)] #[diag(lint_identifier_non_ascii_char)] diff --git a/compiler/rustc_lint/src/multiple_supertrait_upcastable.rs b/compiler/rustc_lint/src/multiple_supertrait_upcastable.rs new file mode 100644 index 00000000000..c2ed0e19f40 --- /dev/null +++ b/compiler/rustc_lint/src/multiple_supertrait_upcastable.rs @@ -0,0 +1,60 @@ +use crate::{LateContext, LateLintPass, LintContext}; + +use rustc_hir as hir; +use rustc_span::sym; + +declare_lint! { + /// The `multiple_supertrait_upcastable` lint detects when an object-safe trait has multiple + /// supertraits. + /// + /// ### Example + /// + /// ```rust + /// trait A {} + /// trait B {} + /// + /// #[warn(multiple_supertrait_upcastable)] + /// trait C: A + B {} + /// ``` + /// + /// {{produces}} + /// + /// ### Explanation + /// + /// To support upcasting with multiple supertraits, we need to store multiple vtables and this + /// can result in extra space overhead, even if no code actually uses upcasting. + /// This lint allows users to identify when such scenarios occur and to decide whether the + /// additional overhead is justified. + pub MULTIPLE_SUPERTRAIT_UPCASTABLE, + Allow, + "detect when an object-safe trait has multiple supertraits", + @feature_gate = sym::multiple_supertrait_upcastable; +} + +declare_lint_pass!(MultipleSupertraitUpcastable => [MULTIPLE_SUPERTRAIT_UPCASTABLE]); + +impl<'tcx> LateLintPass<'tcx> for MultipleSupertraitUpcastable { + fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'tcx>) { + let def_id = item.owner_id.to_def_id(); + // NOTE(nbdd0121): use `object_safety_violations` instead of `check_is_object_safe` because + // the latter will report `where_clause_object_safety` lint. + if let hir::ItemKind::Trait(_, _, _, _, _) = item.kind + && cx.tcx.object_safety_violations(def_id).is_empty() + { + let direct_super_traits_iter = cx.tcx + .super_predicates_of(def_id) + .predicates + .into_iter() + .filter_map(|(pred, _)| pred.to_opt_poly_trait_pred()); + if direct_super_traits_iter.count() > 1 { + cx.emit_spanned_lint( + MULTIPLE_SUPERTRAIT_UPCASTABLE, + cx.tcx.def_span(def_id), + crate::lints::MultipleSupertraitUpcastable { + ident: item.ident + }, + ); + } + } + } +} diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs index 30ca0b8060d..f1119214be4 100644 --- a/compiler/rustc_span/src/symbol.rs +++ b/compiler/rustc_span/src/symbol.rs @@ -955,6 +955,7 @@ symbols! { mul, mul_assign, mul_with_overflow, + multiple_supertrait_upcastable, must_not_suspend, must_use, naked, diff --git a/library/alloc/src/lib.rs b/library/alloc/src/lib.rs index ca75c3895f4..76dabfb429d 100644 --- a/library/alloc/src/lib.rs +++ b/library/alloc/src/lib.rs @@ -87,6 +87,7 @@ #![warn(missing_debug_implementations)] #![warn(missing_docs)] #![allow(explicit_outlives_requirements)] +#![cfg_attr(not(bootstrap), warn(multiple_supertrait_upcastable))] // // Library features: #![feature(alloc_layout_extra)] @@ -195,6 +196,7 @@ #![feature(c_unwind)] #![feature(with_negative_coherence)] #![cfg_attr(test, feature(panic_update_hook))] +#![cfg_attr(not(bootstrap), feature(multiple_supertrait_upcastable))] // // Rustdoc features: #![feature(doc_cfg)] diff --git a/library/core/src/error.rs b/library/core/src/error.rs index 7152300abcb..d2fac23ff18 100644 --- a/library/core/src/error.rs +++ b/library/core/src/error.rs @@ -28,6 +28,7 @@ use crate::fmt::{Debug, Display}; #[stable(feature = "rust1", since = "1.0.0")] #[cfg_attr(not(test), rustc_diagnostic_item = "Error")] #[rustc_has_incoherent_inherent_impls] +#[cfg_attr(not(bootstrap), allow(multiple_supertrait_upcastable))] pub trait Error: Debug + Display { /// The lower-level source of this error, if any. /// diff --git a/library/core/src/lib.rs b/library/core/src/lib.rs index 8790649abe6..6dfe36e6926 100644 --- a/library/core/src/lib.rs +++ b/library/core/src/lib.rs @@ -95,6 +95,7 @@ #![warn(missing_docs)] #![allow(explicit_outlives_requirements)] #![allow(incomplete_features)] +#![cfg_attr(not(bootstrap), warn(multiple_supertrait_upcastable))] // // Library features: #![feature(const_align_offset)] @@ -235,6 +236,7 @@ #![feature(unsized_fn_params)] #![feature(asm_const)] #![feature(const_transmute_copy)] +#![cfg_attr(not(bootstrap), feature(multiple_supertrait_upcastable))] // // Target features: #![feature(arm_target_feature)] diff --git a/tests/ui/feature-gates/feature-gate-multiple_supertrait_upcastable.rs b/tests/ui/feature-gates/feature-gate-multiple_supertrait_upcastable.rs new file mode 100644 index 00000000000..0467dea621b --- /dev/null +++ b/tests/ui/feature-gates/feature-gate-multiple_supertrait_upcastable.rs @@ -0,0 +1,12 @@ +// check-pass + +#![deny(multiple_supertrait_upcastable)] +//~^ WARNING unknown lint: `multiple_supertrait_upcastable` +//~| WARNING unknown lint: `multiple_supertrait_upcastable` +//~| WARNING unknown lint: `multiple_supertrait_upcastable` +#![warn(multiple_supertrait_upcastable)] +//~^ WARNING unknown lint: `multiple_supertrait_upcastable` +//~| WARNING unknown lint: `multiple_supertrait_upcastable` +//~| WARNING unknown lint: `multiple_supertrait_upcastable` + +fn main() {} diff --git a/tests/ui/feature-gates/feature-gate-multiple_supertrait_upcastable.stderr b/tests/ui/feature-gates/feature-gate-multiple_supertrait_upcastable.stderr new file mode 100644 index 00000000000..1f725f35417 --- /dev/null +++ b/tests/ui/feature-gates/feature-gate-multiple_supertrait_upcastable.stderr @@ -0,0 +1,57 @@ +warning: unknown lint: `multiple_supertrait_upcastable` + --> $DIR/feature-gate-multiple_supertrait_upcastable.rs:3:1 + | +LL | #![deny(multiple_supertrait_upcastable)] + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = note: the `multiple_supertrait_upcastable` lint is unstable + = help: add `#![feature(multiple_supertrait_upcastable)]` to the crate attributes to enable + = note: `#[warn(unknown_lints)]` on by default + +warning: unknown lint: `multiple_supertrait_upcastable` + --> $DIR/feature-gate-multiple_supertrait_upcastable.rs:7:1 + | +LL | #![warn(multiple_supertrait_upcastable)] + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = note: the `multiple_supertrait_upcastable` lint is unstable + = help: add `#![feature(multiple_supertrait_upcastable)]` to the crate attributes to enable + +warning: unknown lint: `multiple_supertrait_upcastable` + --> $DIR/feature-gate-multiple_supertrait_upcastable.rs:3:1 + | +LL | #![deny(multiple_supertrait_upcastable)] + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = note: the `multiple_supertrait_upcastable` lint is unstable + = help: add `#![feature(multiple_supertrait_upcastable)]` to the crate attributes to enable + +warning: unknown lint: `multiple_supertrait_upcastable` + --> $DIR/feature-gate-multiple_supertrait_upcastable.rs:7:1 + | +LL | #![warn(multiple_supertrait_upcastable)] + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = note: the `multiple_supertrait_upcastable` lint is unstable + = help: add `#![feature(multiple_supertrait_upcastable)]` to the crate attributes to enable + +warning: unknown lint: `multiple_supertrait_upcastable` + --> $DIR/feature-gate-multiple_supertrait_upcastable.rs:3:1 + | +LL | #![deny(multiple_supertrait_upcastable)] + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = note: the `multiple_supertrait_upcastable` lint is unstable + = help: add `#![feature(multiple_supertrait_upcastable)]` to the crate attributes to enable + +warning: unknown lint: `multiple_supertrait_upcastable` + --> $DIR/feature-gate-multiple_supertrait_upcastable.rs:7:1 + | +LL | #![warn(multiple_supertrait_upcastable)] + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = note: the `multiple_supertrait_upcastable` lint is unstable + = help: add `#![feature(multiple_supertrait_upcastable)]` to the crate attributes to enable + +warning: 6 warnings emitted + diff --git a/tests/ui/traits/trait-upcasting/multiple_supertrait_upcastable.rs b/tests/ui/traits/trait-upcasting/multiple_supertrait_upcastable.rs new file mode 100644 index 00000000000..3c6ab86e4c6 --- /dev/null +++ b/tests/ui/traits/trait-upcasting/multiple_supertrait_upcastable.rs @@ -0,0 +1,10 @@ +#![feature(multiple_supertrait_upcastable)] +#![deny(multiple_supertrait_upcastable)] + +trait A {} +trait B {} + +trait C: A + B {} +//~^ ERROR `C` is object-safe and has multiple supertraits + +fn main() {} diff --git a/tests/ui/traits/trait-upcasting/multiple_supertrait_upcastable.stderr b/tests/ui/traits/trait-upcasting/multiple_supertrait_upcastable.stderr new file mode 100644 index 00000000000..ad80a009ece --- /dev/null +++ b/tests/ui/traits/trait-upcasting/multiple_supertrait_upcastable.stderr @@ -0,0 +1,14 @@ +error: `C` is object-safe and has multiple supertraits + --> $DIR/multiple_supertrait_upcastable.rs:7:1 + | +LL | trait C: A + B {} + | ^^^^^^^^^^^^^^ + | +note: the lint level is defined here + --> $DIR/multiple_supertrait_upcastable.rs:2:9 + | +LL | #![deny(multiple_supertrait_upcastable)] + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +error: aborting due to previous error +