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Revert recent changes to dead code analysis (beta flavor) #128606

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merged 5 commits into from
Aug 5, 2024
Merged

Revert recent changes to dead code analysis (beta flavor) #128606

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d99ba60
Revert "Rollup merge of #127107 - mu001999-contrib:dead/enhance-2, r=…
compiler-errors Jul 30, 2024
d571104
Revert "Rollup merge of #126618 - mu001999-contrib:dead/enhance, r=pn…
compiler-errors Jul 30, 2024
ad90fa6
Revert "Rollup merge of #126315 - mu001999-contrib:fix/126289, r=petr…
compiler-errors Jul 30, 2024
35779db
Revert "Rollup merge of #125572 - mu001999-contrib:dead/enhance, r=pn…
compiler-errors Jul 30, 2024
eeaf3ce
Bless test fallout
compiler-errors Aug 3, 2024
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184 changes: 63 additions & 121 deletions compiler/rustc_passes/src/dead.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -15,7 +15,7 @@ use rustc_hir::{Node, PatKind, TyKind};
use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
use rustc_middle::middle::privacy::Level;
use rustc_middle::query::Providers;
use rustc_middle::ty::{self, AssocItemContainer, TyCtxt};
use rustc_middle::ty::{self, TyCtxt};
use rustc_middle::{bug, span_bug};
use rustc_session::lint;
use rustc_session::lint::builtin::DEAD_CODE;
Expand Down Expand Up @@ -43,63 +43,16 @@ fn should_explore(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
)
}

struct Publicness {
ty_is_public: bool,
ty_and_all_fields_are_public: bool,
}

impl Publicness {
fn new(ty_is_public: bool, ty_and_all_fields_are_public: bool) -> Self {
Self { ty_is_public, ty_and_all_fields_are_public }
}
}

fn struct_all_fields_are_public(tcx: TyCtxt<'_>, id: DefId) -> bool {
// treat PhantomData and positional ZST as public,
// we don't want to lint types which only have them,
// cause it's a common way to use such types to check things like well-formedness
tcx.adt_def(id).all_fields().all(|field| {
let field_type = tcx.type_of(field.did).instantiate_identity();
if field_type.is_phantom_data() {
return true;
}
let is_positional = field.name.as_str().starts_with(|c: char| c.is_ascii_digit());
if is_positional
&& tcx
.layout_of(tcx.param_env(field.did).and(field_type))
.map_or(true, |layout| layout.is_zst())
{
return true;
}
field.vis.is_public()
})
}

/// check struct and its fields are public or not,
/// for enum and union, just check they are public,
/// and doesn't solve types like &T for now, just skip them
fn ty_ref_to_pub_struct(tcx: TyCtxt<'_>, ty: &hir::Ty<'_>) -> Publicness {
fn ty_ref_to_pub_struct(tcx: TyCtxt<'_>, ty: &hir::Ty<'_>) -> bool {
if let TyKind::Path(hir::QPath::Resolved(_, path)) = ty.kind
&& let Res::Def(def_kind, def_id) = path.res
&& def_id.is_local()
&& matches!(def_kind, DefKind::Struct | DefKind::Enum | DefKind::Union)
{
return match def_kind {
DefKind::Enum | DefKind::Union => {
let ty_is_public = tcx.visibility(def_id).is_public();
Publicness::new(ty_is_public, ty_is_public)
}
DefKind::Struct => {
let ty_is_public = tcx.visibility(def_id).is_public();
Publicness::new(
ty_is_public,
ty_is_public && struct_all_fields_are_public(tcx, def_id),
)
}
_ => Publicness::new(true, true),
};
tcx.visibility(def_id).is_public()
} else {
true
}

Publicness::new(true, true)
}

/// Determine if a work from the worklist is coming from a `#[allow]`
Expand Down Expand Up @@ -155,10 +108,7 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {

fn handle_res(&mut self, res: Res) {
match res {
Res::Def(
DefKind::Const | DefKind::AssocConst | DefKind::AssocTy | DefKind::TyAlias,
def_id,
) => {
Res::Def(DefKind::Const | DefKind::AssocConst | DefKind::TyAlias, def_id) => {
self.check_def_id(def_id);
}
_ if self.in_pat => {}
Expand Down Expand Up @@ -277,10 +227,7 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
pats: &[hir::PatField<'_>],
) {
let variant = match self.typeck_results().node_type(lhs.hir_id).kind() {
ty::Adt(adt, _) => {
self.check_def_id(adt.did());
adt.variant_of_res(res)
}
ty::Adt(adt, _) => adt.variant_of_res(res),
_ => span_bug!(lhs.span, "non-ADT in struct pattern"),
};
for pat in pats {
Expand All @@ -300,10 +247,7 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
dotdot: hir::DotDotPos,
) {
let variant = match self.typeck_results().node_type(lhs.hir_id).kind() {
ty::Adt(adt, _) => {
self.check_def_id(adt.did());
adt.variant_of_res(res)
}
ty::Adt(adt, _) => adt.variant_of_res(res),
_ => {
self.tcx.dcx().span_delayed_bug(lhs.span, "non-ADT in tuple struct pattern");
return;
Expand Down Expand Up @@ -408,6 +352,31 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
return false;
}

// don't ignore impls for Enums and pub Structs whose methods don't have self receiver,
// cause external crate may call such methods to construct values of these types
if let Some(local_impl_of) = impl_of.as_local()
&& let Some(local_def_id) = def_id.as_local()
&& let Some(fn_sig) =
self.tcx.hir().fn_sig_by_hir_id(self.tcx.local_def_id_to_hir_id(local_def_id))
&& matches!(fn_sig.decl.implicit_self, hir::ImplicitSelfKind::None)
&& let TyKind::Path(hir::QPath::Resolved(_, path)) =
self.tcx.hir().expect_item(local_impl_of).expect_impl().self_ty.kind
&& let Res::Def(def_kind, did) = path.res
{
match def_kind {
// for example, #[derive(Default)] pub struct T(i32);
// external crate can call T::default() to construct T,
// so that don't ignore impl Default for pub Enum and Structs
DefKind::Struct | DefKind::Union if self.tcx.visibility(did).is_public() => {
return false;
}
// don't ignore impl Default for Enums,
// cause we don't know which variant is constructed
DefKind::Enum => return false,
_ => (),
};
}

if let Some(trait_of) = self.tcx.trait_id_of_impl(impl_of)
&& self.tcx.has_attr(trait_of, sym::rustc_trivial_field_reads)
{
Expand Down Expand Up @@ -450,7 +419,7 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
intravisit::walk_item(self, item)
}
hir::ItemKind::ForeignMod { .. } => {}
hir::ItemKind::Trait(_, _, _, _, trait_item_refs) => {
hir::ItemKind::Trait(..) => {
for impl_def_id in self.tcx.all_impls(item.owner_id.to_def_id()) {
if let Some(local_def_id) = impl_def_id.as_local()
&& let ItemKind::Impl(impl_ref) =
Expand All @@ -463,12 +432,7 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
intravisit::walk_path(self, impl_ref.of_trait.unwrap().path);
}
}
// mark assoc ty live if the trait is live
for trait_item in trait_item_refs {
if let hir::AssocItemKind::Type = trait_item.kind {
self.check_def_id(trait_item.id.owner_id.to_def_id());
}
}

intravisit::walk_item(self, item)
}
_ => intravisit::walk_item(self, item),
Expand All @@ -485,12 +449,11 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
&& let ItemKind::Impl(impl_ref) =
self.tcx.hir().expect_item(local_impl_id).kind
{
if !ty_ref_to_pub_struct(self.tcx, impl_ref.self_ty)
.ty_and_all_fields_are_public
if !matches!(trait_item.kind, hir::TraitItemKind::Type(..))
&& !ty_ref_to_pub_struct(self.tcx, impl_ref.self_ty)
{
// skip impl-items of non pure pub ty,
// cause we don't know the ty is constructed or not,
// check these later in `solve_rest_impl_items`
// skip methods of private ty,
// they would be solved in `solve_rest_impl_items`
continue;
}

Expand Down Expand Up @@ -571,21 +534,22 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
&& let Some(local_def_id) = def_id.as_local()
&& matches!(def_kind, DefKind::Struct | DefKind::Enum | DefKind::Union)
{
if self.tcx.visibility(impl_item_id).is_public() {
// for the public method, we don't know the trait item is used or not,
// so we mark the method live if the self is used
return self.live_symbols.contains(&local_def_id);
}

if let Some(trait_item_id) = self.tcx.associated_item(impl_item_id).trait_item_def_id
&& let Some(local_id) = trait_item_id.as_local()
{
// for the local impl item, we can know the trait item is used or not,
// for the private method, we can know the trait item is used or not,
// so we mark the method live if the self is used and the trait item is used
self.live_symbols.contains(&local_id) && self.live_symbols.contains(&local_def_id)
} else {
// for the foreign method and inherent pub method,
// we don't know the trait item or the method is used or not,
// so we mark the method live if the self is used
self.live_symbols.contains(&local_def_id)
return self.live_symbols.contains(&local_id)
&& self.live_symbols.contains(&local_def_id);
}
} else {
false
}
false
}
}

Expand Down Expand Up @@ -671,9 +635,6 @@ impl<'tcx> Visitor<'tcx> for MarkSymbolVisitor<'tcx> {
self.handle_field_pattern_match(pat, res, fields);
}
PatKind::Path(ref qpath) => {
if let ty::Adt(adt, _) = self.typeck_results().node_type(pat.hir_id).kind() {
self.check_def_id(adt.did());
}
let res = self.typeck_results().qpath_res(qpath, pat.hir_id);
self.handle_res(res);
}
Expand Down Expand Up @@ -810,9 +771,7 @@ fn check_item<'tcx>(
.iter()
.filter_map(|def_id| def_id.as_local());

let self_ty = tcx.hir().item(id).expect_impl().self_ty;
let Publicness { ty_is_public, ty_and_all_fields_are_public } =
ty_ref_to_pub_struct(tcx, self_ty);
let ty_is_pub = ty_ref_to_pub_struct(tcx, tcx.hir().item(id).expect_impl().self_ty);

// And we access the Map here to get HirId from LocalDefId
for local_def_id in local_def_ids {
Expand All @@ -828,19 +787,18 @@ fn check_item<'tcx>(
// for trait impl blocks,
// mark the method live if the self_ty is public,
// or the method is public and may construct self
if tcx.visibility(local_def_id).is_public()
&& (ty_and_all_fields_are_public || (ty_is_public && may_construct_self))
if of_trait
&& (!matches!(tcx.def_kind(local_def_id), DefKind::AssocFn)
|| tcx.visibility(local_def_id).is_public()
&& (ty_is_pub || may_construct_self))
{
// if the impl item is public,
// and the ty may be constructed or can be constructed in foreign crates,
// mark the impl item live
worklist.push((local_def_id, ComesFromAllowExpect::No));
} else if let Some(comes_from_allow) =
has_allow_dead_code_or_lang_attr(tcx, local_def_id)
{
worklist.push((local_def_id, comes_from_allow));
} else if of_trait || tcx.visibility(local_def_id).is_public() && ty_is_public {
// private impl items of traits || public impl items not constructs self
} else if of_trait {
// private method || public method not constructs self
unsolved_impl_items.push((id, local_def_id));
}
}
Expand All @@ -866,13 +824,10 @@ fn check_trait_item(
worklist: &mut Vec<(LocalDefId, ComesFromAllowExpect)>,
id: hir::TraitItemId,
) {
use hir::TraitItemKind::{Const, Fn, Type};
if matches!(
tcx.def_kind(id.owner_id),
DefKind::AssocConst | DefKind::AssocTy | DefKind::AssocFn
) {
use hir::TraitItemKind::{Const, Fn};
if matches!(tcx.def_kind(id.owner_id), DefKind::AssocConst | DefKind::AssocFn) {
let trait_item = tcx.hir().trait_item(id);
if matches!(trait_item.kind, Const(_, Some(_)) | Type(_, Some(_)) | Fn(..))
if matches!(trait_item.kind, Const(_, Some(_)) | Fn(..))
&& let Some(comes_from_allow) =
has_allow_dead_code_or_lang_attr(tcx, trait_item.owner_id.def_id)
{
Expand Down Expand Up @@ -910,14 +865,6 @@ fn create_and_seed_worklist(
effective_vis
.is_public_at_level(Level::Reachable)
.then_some(id)
.filter(|&id|
// checks impls, impl-items and pub structs with all public fields later
match tcx.def_kind(id) {
DefKind::Impl { .. } => false,
DefKind::AssocConst | DefKind::AssocTy | DefKind::AssocFn => !matches!(tcx.associated_item(id).container, AssocItemContainer::ImplContainer),
DefKind::Struct => struct_all_fields_are_public(tcx, id.to_def_id()) || has_allow_dead_code_or_lang_attr(tcx, id).is_some(),
_ => true
})
.map(|id| (id, ComesFromAllowExpect::No))
})
// Seed entry point
Expand Down Expand Up @@ -1201,7 +1148,6 @@ impl<'tcx> DeadVisitor<'tcx> {
}
match self.tcx.def_kind(def_id) {
DefKind::AssocConst
| DefKind::AssocTy
| DefKind::AssocFn
| DefKind::Fn
| DefKind::Static { .. }
Expand Down Expand Up @@ -1243,14 +1189,10 @@ fn check_mod_deathness(tcx: TyCtxt<'_>, module: LocalModDefId) {
|| (def_kind == DefKind::Trait && live_symbols.contains(&item.owner_id.def_id))
{
for &def_id in tcx.associated_item_def_ids(item.owner_id.def_id) {
// We have diagnosed unused assocs in traits
// We have diagnosed unused methods in traits
if matches!(def_kind, DefKind::Impl { of_trait: true })
&& matches!(tcx.def_kind(def_id), DefKind::AssocConst | DefKind::AssocTy | DefKind::AssocFn)
// skip unused public inherent methods,
// cause we have diagnosed unconstructed struct
|| matches!(def_kind, DefKind::Impl { of_trait: false })
&& tcx.visibility(def_id).is_public()
&& ty_ref_to_pub_struct(tcx, tcx.hir().item(item).expect_impl().self_ty).ty_is_public
&& tcx.def_kind(def_id) == DefKind::AssocFn
|| def_kind == DefKind::Trait && tcx.def_kind(def_id) != DefKind::AssocFn
{
continue;
}
Expand Down
1 change: 1 addition & 0 deletions library/core/src/default.rs
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Expand Up @@ -103,6 +103,7 @@ use crate::ascii::Char as AsciiChar;
/// ```
#[cfg_attr(not(test), rustc_diagnostic_item = "Default")]
#[stable(feature = "rust1", since = "1.0.0")]
#[cfg_attr(not(bootstrap), rustc_trivial_field_reads)]
pub trait Default: Sized {
/// Returns the "default value" for a type.
///
Expand Down
10 changes: 5 additions & 5 deletions tests/codegen-units/item-collection/generic-impl.rs
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Expand Up @@ -22,16 +22,16 @@ impl<T> Struct<T> {
}
}

pub struct _LifeTimeOnly<'a> {
pub struct LifeTimeOnly<'a> {
_a: &'a u32,
}

impl<'a> _LifeTimeOnly<'a> {
//~ MONO_ITEM fn _LifeTimeOnly::<'_>::foo
impl<'a> LifeTimeOnly<'a> {
//~ MONO_ITEM fn LifeTimeOnly::<'_>::foo
pub fn foo(&self) {}
//~ MONO_ITEM fn _LifeTimeOnly::<'_>::bar
//~ MONO_ITEM fn LifeTimeOnly::<'_>::bar
pub fn bar(&'a self) {}
//~ MONO_ITEM fn _LifeTimeOnly::<'_>::baz
//~ MONO_ITEM fn LifeTimeOnly::<'_>::baz
pub fn baz<'b>(&'b self) {}

pub fn non_instantiated<T>(&self) {}
Expand Down
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