From e44a7386c27f821515804fa90ed39ca1e931f8de Mon Sep 17 00:00:00 2001 From: Oli Scherer Date: Thu, 24 Jul 2025 08:15:03 +0000 Subject: [PATCH] Remove dead code and extend test coverage and diagnostics around it We lost the following comment during refactorings: The current code for niche-filling relies on variant indices instead of actual discriminants, so enums with explicit discriminants (RFC 2363) would misbehave. --- compiler/rustc_abi/src/layout.rs | 12 +----- .../rustc_hir_analysis/src/check/check.rs | 38 ++++++++++++++----- compiler/rustc_ty_utils/src/layout.rs | 8 ---- .../crates/hir-ty/src/layout/adt.rs | 16 ++------ .../arbitrary_enum_discriminant-no-repr.rs | 19 +++++++--- ...arbitrary_enum_discriminant-no-repr.stderr | 20 ++++++++-- 6 files changed, 65 insertions(+), 48 deletions(-) diff --git a/compiler/rustc_abi/src/layout.rs b/compiler/rustc_abi/src/layout.rs index 80b44e432eeb0..716bb716cdb57 100644 --- a/compiler/rustc_abi/src/layout.rs +++ b/compiler/rustc_abi/src/layout.rs @@ -313,7 +313,6 @@ impl LayoutCalculator { scalar_valid_range: (Bound, Bound), discr_range_of_repr: impl Fn(i128, i128) -> (Integer, bool), discriminants: impl Iterator, - dont_niche_optimize_enum: bool, always_sized: bool, ) -> LayoutCalculatorResult { let (present_first, present_second) = { @@ -352,13 +351,7 @@ impl LayoutCalculator { // structs. (We have also handled univariant enums // that allow representation optimization.) assert!(is_enum); - self.layout_of_enum( - repr, - variants, - discr_range_of_repr, - discriminants, - dont_niche_optimize_enum, - ) + self.layout_of_enum(repr, variants, discr_range_of_repr, discriminants) } } @@ -599,7 +592,6 @@ impl LayoutCalculator { variants: &IndexSlice>, discr_range_of_repr: impl Fn(i128, i128) -> (Integer, bool), discriminants: impl Iterator, - dont_niche_optimize_enum: bool, ) -> LayoutCalculatorResult { // Until we've decided whether to use the tagged or // niche filling LayoutData, we don't want to intern the @@ -618,7 +610,7 @@ impl LayoutCalculator { } let calculate_niche_filling_layout = || -> Option> { - if dont_niche_optimize_enum { + if repr.inhibit_enum_layout_opt() { return None; } diff --git a/compiler/rustc_hir_analysis/src/check/check.rs b/compiler/rustc_hir_analysis/src/check/check.rs index 03c026cd6c892..bb1de5bcfc3b7 100644 --- a/compiler/rustc_hir_analysis/src/check/check.rs +++ b/compiler/rustc_hir_analysis/src/check/check.rs @@ -1642,20 +1642,40 @@ fn check_enum(tcx: TyCtxt<'_>, def_id: LocalDefId) { if def.repr().int.is_none() { let is_unit = |var: &ty::VariantDef| matches!(var.ctor_kind(), Some(CtorKind::Const)); - let has_disr = |var: &ty::VariantDef| matches!(var.discr, ty::VariantDiscr::Explicit(_)); + let get_disr = |var: &ty::VariantDef| match var.discr { + ty::VariantDiscr::Explicit(disr) => Some(disr), + ty::VariantDiscr::Relative(_) => None, + }; - let has_non_units = def.variants().iter().any(|var| !is_unit(var)); - let disr_units = def.variants().iter().any(|var| is_unit(var) && has_disr(var)); - let disr_non_unit = def.variants().iter().any(|var| !is_unit(var) && has_disr(var)); + let non_unit = def.variants().iter().find(|var| !is_unit(var)); + let disr_unit = + def.variants().iter().filter(|var| is_unit(var)).find_map(|var| get_disr(var)); + let disr_non_unit = + def.variants().iter().filter(|var| !is_unit(var)).find_map(|var| get_disr(var)); - if disr_non_unit || (disr_units && has_non_units) { - struct_span_code_err!( + if disr_non_unit.is_some() || (disr_unit.is_some() && non_unit.is_some()) { + let mut err = struct_span_code_err!( tcx.dcx(), tcx.def_span(def_id), E0732, - "`#[repr(inttype)]` must be specified" - ) - .emit(); + "`#[repr(inttype)]` must be specified for enums with explicit discriminants and non-unit variants" + ); + if let Some(disr_non_unit) = disr_non_unit { + err.span_label( + tcx.def_span(disr_non_unit), + "explicit discriminant on non-unit variant specified here", + ); + } else { + err.span_label( + tcx.def_span(disr_unit.unwrap()), + "explicit discriminant specified here", + ); + err.span_label( + tcx.def_span(non_unit.unwrap().def_id), + "non-unit discriminant declared here", + ); + } + err.emit(); } } diff --git a/compiler/rustc_ty_utils/src/layout.rs b/compiler/rustc_ty_utils/src/layout.rs index 163e2b3088374..79f7e228e2adc 100644 --- a/compiler/rustc_ty_utils/src/layout.rs +++ b/compiler/rustc_ty_utils/src/layout.rs @@ -603,12 +603,6 @@ fn layout_of_uncached<'tcx>( .flatten() }; - let dont_niche_optimize_enum = def.repr().inhibit_enum_layout_opt() - || def - .variants() - .iter_enumerated() - .any(|(i, v)| v.discr != ty::VariantDiscr::Relative(i.as_u32())); - let maybe_unsized = def.is_struct() && def.non_enum_variant().tail_opt().is_some_and(|last_field| { let typing_env = ty::TypingEnv::post_analysis(tcx, def.did()); @@ -625,7 +619,6 @@ fn layout_of_uncached<'tcx>( tcx.layout_scalar_valid_range(def.did()), get_discriminant_type, discriminants_iter(), - dont_niche_optimize_enum, !maybe_unsized, ) .map_err(|err| map_error(cx, ty, err))?; @@ -651,7 +644,6 @@ fn layout_of_uncached<'tcx>( tcx.layout_scalar_valid_range(def.did()), get_discriminant_type, discriminants_iter(), - dont_niche_optimize_enum, !maybe_unsized, ) else { bug!("failed to compute unsized layout of {ty:?}"); diff --git a/src/tools/rust-analyzer/crates/hir-ty/src/layout/adt.rs b/src/tools/rust-analyzer/crates/hir-ty/src/layout/adt.rs index 236f316366dc9..372a9dfc43d27 100644 --- a/src/tools/rust-analyzer/crates/hir-ty/src/layout/adt.rs +++ b/src/tools/rust-analyzer/crates/hir-ty/src/layout/adt.rs @@ -3,9 +3,9 @@ use std::{cmp, ops::Bound}; use hir_def::{ - AdtId, VariantId, layout::{Integer, ReprOptions, TargetDataLayout}, signatures::{StructFlags, VariantFields}, + AdtId, VariantId, }; use intern::sym; use rustc_index::IndexVec; @@ -13,9 +13,9 @@ use smallvec::SmallVec; use triomphe::Arc; use crate::{ - Substitution, TraitEnvironment, db::HirDatabase, - layout::{Layout, LayoutError, field_ty}, + layout::{field_ty, Layout, LayoutError}, + Substitution, TraitEnvironment, }; use super::LayoutCx; @@ -85,16 +85,6 @@ pub fn layout_of_adt_query( let d = db.const_eval_discriminant(e.enum_variants(db).variants[id.0].0).ok()?; Some((id, d)) }), - // FIXME: The current code for niche-filling relies on variant indices - // instead of actual discriminants, so enums with - // explicit discriminants (RFC #2363) would misbehave and we should disable - // niche optimization for them. - // The code that do it in rustc: - // repr.inhibit_enum_layout_opt() || def - // .variants() - // .iter_enumerated() - // .any(|(i, v)| v.discr != ty::VariantDiscr::Relative(i.as_u32())) - repr.inhibit_enum_layout_opt(), !matches!(def, AdtId::EnumId(..)) && variants .iter() diff --git a/tests/ui/enum-discriminant/arbitrary_enum_discriminant-no-repr.rs b/tests/ui/enum-discriminant/arbitrary_enum_discriminant-no-repr.rs index a6e5f70fdefa6..6bbafbf1434ef 100644 --- a/tests/ui/enum-discriminant/arbitrary_enum_discriminant-no-repr.rs +++ b/tests/ui/enum-discriminant/arbitrary_enum_discriminant-no-repr.rs @@ -1,8 +1,17 @@ -#![crate_type="lib"] +#![crate_type = "lib"] +// Test that if any variant is non-unit, +// we need a repr. enum Enum { -//~^ ERROR `#[repr(inttype)]` must be specified - Unit = 1, - Tuple() = 2, - Struct{} = 3, + //~^ ERROR `#[repr(inttype)]` must be specified + Unit = 1, + Tuple(), + Struct {}, +} + +// Test that if any non-unit variant has an explicit +// discriminant we need a repr. +enum Enum2 { + //~^ ERROR `#[repr(inttype)]` must be specified + Tuple() = 2, } diff --git a/tests/ui/enum-discriminant/arbitrary_enum_discriminant-no-repr.stderr b/tests/ui/enum-discriminant/arbitrary_enum_discriminant-no-repr.stderr index 3b718c6465bdf..35c0208951aeb 100644 --- a/tests/ui/enum-discriminant/arbitrary_enum_discriminant-no-repr.stderr +++ b/tests/ui/enum-discriminant/arbitrary_enum_discriminant-no-repr.stderr @@ -1,9 +1,23 @@ -error[E0732]: `#[repr(inttype)]` must be specified - --> $DIR/arbitrary_enum_discriminant-no-repr.rs:3:1 +error[E0732]: `#[repr(inttype)]` must be specified for enums with explicit discriminants and non-unit variants + --> $DIR/arbitrary_enum_discriminant-no-repr.rs:5:1 | LL | enum Enum { | ^^^^^^^^^ +LL | +LL | Unit = 1, + | - explicit discriminant specified here +LL | Tuple(), + | ----- non-unit discriminant declared here -error: aborting due to 1 previous error +error[E0732]: `#[repr(inttype)]` must be specified for enums with explicit discriminants and non-unit variants + --> $DIR/arbitrary_enum_discriminant-no-repr.rs:14:1 + | +LL | enum Enum2 { + | ^^^^^^^^^^ +LL | +LL | Tuple() = 2, + | - explicit discriminant on non-unit variant specified here + +error: aborting due to 2 previous errors For more information about this error, try `rustc --explain E0732`.