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Auto merge of #123340 - fmease:rustdoc-simplify-auto-trait-impl-synth, r=GuillaumeGomez

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rustdoc: heavily simplify the synthesis of auto trait impls

`gd --numstat HEAD~2 HEAD src/librustdoc/clean/auto_trait.rs`
**+315 -705** 🟩🟥🟥🟥⬛

---

As outlined in issue #113015, there are currently 3[^1] large separate routines that “clean” `rustc_middle::ty` data types related to generics & predicates to rustdoc data types. Every single one has their own kinds of bugs. While I've patched a lot of bugs in each of the routines in the past, it's about time to unify them. This PR is only the first in a series. It completely **yanks** the custom “bounds cleaning” of mod `auto_trait` and reuses the routines found in mod `simplify`. As alluded to, `simplify` is also flawed but it's still more complete than `auto_trait`'s routines. [See also my review comment over at `tests/rustdoc/synthetic_auto/bounds.rs`](https://github.com/rust-lang/rust/pull/123340#discussion_r1546900539).

This is preparatory work for rewriting “bounds cleaning” from scratch in follow-up PRs in order to finally [fix] #113015.

Apart from that, I've eliminated all potential sources of *instability* in the rendered output.
See also #119597. I'm pretty sure this fixes #119597.

This PR does not attempt to fix [any other issues related to synthetic auto trait impls](https://github.com/rust-lang/rust/issues?q=is%3Aissue+is%3Aopen+label%3AA-synthetic-impls%20label%3AA-auto-traits).
However, it's definitely meant to be a *stepping stone* by making `auto_trait` more contributor-friendly.

---

* Replace `FxHash{Map,Set}` with `FxIndex{Map,Set}` to guarantee a stable iteration order
  * Or as a perf opt, `UnordSet` (a thin wrapper around `FxHashSet`) in cases where we never iterate over the set.
  * Yes, we do make use of `swap_remove` but that shouldn't matter since all the callers are deterministic. It does make the output less “predictable” but it's still better than before. Ofc, I rely on `rustc_infer` being deterministic. I hope that holds.
* Utilizing `clean::simplify` over the custom “bounds cleaning” routines wipes out the last reference to `collect_referenced_late_bound_regions` in rustdoc (`simplify` uses `bound_vars`) which was a source of instability / unpredictability (cc #116388)
* Remove the types `RegionTarget` and `RegionDeps` from `librustdoc`. They were duplicates of the identical types found in `rustc`. Just import them from `rustc`. For some reason, they were duplicated when splitting `auto_trait` in two in #49711.
* Get rid of the useless “type namespace” `AutoTraitFinder` in `librustdoc`
  * The struct only held a `DocContext`, it was over-engineered
  * Turn the associated functions into free ones
    * Eliminates rightward drift; increases legibility
  * `rustc` also contains a useless `AutoTraitFinder` struct but I plan on removing that in a follow-up PR
* Rename a bunch of methods to be way more descriptive
* Eliminate `use super::*;`
  * Lead to `clean/mod.rs` accumulating a lot of unnecessary imports
  * Made `auto_traits` less modular
* Eliminate a custom `TypeFolder`: We can just use the rustc helper `fold_regions` which does that for us

I plan on adding extensive documentation to `librustdoc`'s `auto_trait` in follow-up PRs.
I don't want to do that in this PR because further refactoring & bug fix PRs may alter the overall structure of `librustdoc`'s & `rustc`'s `auto_trait` modules to a great degree. I'm slowly digging into the dark details of `rustc`'s `auto_trait` module again and once I have the full picture I will be able to provide proper docs.

---

While this PR does indeed touch `rustc`'s `auto_trait` — mostly tiny refactorings — I argue this PR doesn't need any compiler reviewers next to rustdoc ones since that module falls under the purview of rustdoc — it used to be part of `librustdoc` after all (#49711).

Sorry for not having split this into more commits. If you'd like me to I can try to split it into more atomic commits retroactively. However, I don't know if that would actually make reviewing easier. I think the best way to review this might just be to place the master version of `auto_trait` on the left of your screen and the patched one on the right, not joking.

r? `@GuillaumeGomez`

[^1]: Or even 4 depending on the way you're counting.
This commit is contained in:
bors 2024-04-02 12:13:44 +00:00
commit 5dbaafdb93
11 changed files with 479 additions and 876 deletions
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62
compiler/rustc_trait_selection/src/traits/auto_trait.rs
View File

@ -6,13 +6,13 @@ use super::*;
use crate::errors::UnableToConstructConstantValue; use crate::errors::UnableToConstructConstantValue;
use crate::infer::region_constraints::{Constraint, RegionConstraintData}; use crate::infer::region_constraints::{Constraint, RegionConstraintData};
use crate::traits::project::ProjectAndUnifyResult; use crate::traits::project::ProjectAndUnifyResult;
use rustc_data_structures::fx::{FxIndexMap, FxIndexSet, IndexEntry};
use rustc_data_structures::unord::UnordSet;
use rustc_infer::infer::DefineOpaqueTypes; use rustc_infer::infer::DefineOpaqueTypes;
use rustc_middle::mir::interpret::ErrorHandled; use rustc_middle::mir::interpret::ErrorHandled;
use rustc_middle::ty::{Region, RegionVid}; use rustc_middle::ty::{Region, RegionVid};
use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
use std::collections::hash_map::Entry;
use std::collections::VecDeque; use std::collections::VecDeque;
use std::iter; use std::iter;
@ -25,8 +25,8 @@ pub enum RegionTarget<'tcx> {
#[derive(Default, Debug, Clone)] #[derive(Default, Debug, Clone)]
pub struct RegionDeps<'tcx> { pub struct RegionDeps<'tcx> {
larger: FxIndexSet<RegionTarget<'tcx>>, pub larger: FxIndexSet<RegionTarget<'tcx>>,
smaller: FxIndexSet<RegionTarget<'tcx>>, pub smaller: FxIndexSet<RegionTarget<'tcx>>,
} }
pub enum AutoTraitResult<A> { pub enum AutoTraitResult<A> {
@ -35,17 +35,10 @@ pub enum AutoTraitResult<A> {
NegativeImpl, NegativeImpl,
} }
#[allow(dead_code)]
impl<A> AutoTraitResult<A> {
fn is_auto(&self) -> bool {
matches!(self, AutoTraitResult::PositiveImpl(_) | AutoTraitResult::NegativeImpl)
}
}
pub struct AutoTraitInfo<'cx> { pub struct AutoTraitInfo<'cx> {
pub full_user_env: ty::ParamEnv<'cx>, pub full_user_env: ty::ParamEnv<'cx>,
pub region_data: RegionConstraintData<'cx>, pub region_data: RegionConstraintData<'cx>,
pub vid_to_region: FxHashMap<ty::RegionVid, ty::Region<'cx>>, pub vid_to_region: FxIndexMap<ty::RegionVid, ty::Region<'cx>>,
} }
pub struct AutoTraitFinder<'tcx> { pub struct AutoTraitFinder<'tcx> {
@ -88,19 +81,12 @@ impl<'tcx> AutoTraitFinder<'tcx> {
let infcx = tcx.infer_ctxt().build(); let infcx = tcx.infer_ctxt().build();
let mut selcx = SelectionContext::new(&infcx); let mut selcx = SelectionContext::new(&infcx);
for polarity in [true, false] { for polarity in [ty::PredicatePolarity::Positive, ty::PredicatePolarity::Negative] {
let result = selcx.select(&Obligation::new( let result = selcx.select(&Obligation::new(
tcx, tcx,
ObligationCause::dummy(), ObligationCause::dummy(),
orig_env, orig_env,
ty::TraitPredicate { ty::TraitPredicate { trait_ref, polarity },
trait_ref,
polarity: if polarity {
ty::PredicatePolarity::Positive
} else {
ty::PredicatePolarity::Negative
},
},
)); ));
if let Ok(Some(ImplSource::UserDefined(_))) = result { if let Ok(Some(ImplSource::UserDefined(_))) = result {
debug!( debug!(
@ -114,7 +100,7 @@ impl<'tcx> AutoTraitFinder<'tcx> {
} }
let infcx = tcx.infer_ctxt().build(); let infcx = tcx.infer_ctxt().build();
let mut fresh_preds = FxHashSet::default(); let mut fresh_preds = FxIndexSet::default();
// Due to the way projections are handled by SelectionContext, we need to run // Due to the way projections are handled by SelectionContext, we need to run
// evaluate_predicates twice: once on the original param env, and once on the result of // evaluate_predicates twice: once on the original param env, and once on the result of
@ -239,7 +225,7 @@ impl<'tcx> AutoTraitFinder<'tcx> {
ty: Ty<'tcx>, ty: Ty<'tcx>,
param_env: ty::ParamEnv<'tcx>, param_env: ty::ParamEnv<'tcx>,
user_env: ty::ParamEnv<'tcx>, user_env: ty::ParamEnv<'tcx>,
fresh_preds: &mut FxHashSet<ty::Predicate<'tcx>>, fresh_preds: &mut FxIndexSet<ty::Predicate<'tcx>>,
) -> Option<(ty::ParamEnv<'tcx>, ty::ParamEnv<'tcx>)> { ) -> Option<(ty::ParamEnv<'tcx>, ty::ParamEnv<'tcx>)> {
let tcx = infcx.tcx; let tcx = infcx.tcx;
@ -252,7 +238,7 @@ impl<'tcx> AutoTraitFinder<'tcx> {
let mut select = SelectionContext::new(infcx); let mut select = SelectionContext::new(infcx);
let mut already_visited = FxHashSet::default(); let mut already_visited = UnordSet::new();
let mut predicates = VecDeque::new(); let mut predicates = VecDeque::new();
predicates.push_back(ty::Binder::dummy(ty::TraitPredicate { predicates.push_back(ty::Binder::dummy(ty::TraitPredicate {
trait_ref: ty::TraitRef::new(infcx.tcx, trait_did, [ty]), trait_ref: ty::TraitRef::new(infcx.tcx, trait_did, [ty]),
@ -473,9 +459,9 @@ impl<'tcx> AutoTraitFinder<'tcx> {
fn map_vid_to_region<'cx>( fn map_vid_to_region<'cx>(
&self, &self,
regions: &RegionConstraintData<'cx>, regions: &RegionConstraintData<'cx>,
) -> FxHashMap<ty::RegionVid, ty::Region<'cx>> { ) -> FxIndexMap<ty::RegionVid, ty::Region<'cx>> {
let mut vid_map: FxHashMap<RegionTarget<'cx>, RegionDeps<'cx>> = FxHashMap::default(); let mut vid_map = FxIndexMap::<RegionTarget<'cx>, RegionDeps<'cx>>::default();
let mut finished_map = FxHashMap::default(); let mut finished_map = FxIndexMap::default();
for (constraint, _) in &regions.constraints { for (constraint, _) in &regions.constraints {
match constraint { match constraint {
@ -513,25 +499,22 @@ impl<'tcx> AutoTraitFinder<'tcx> {
} }
while !vid_map.is_empty() { while !vid_map.is_empty() {
#[allow(rustc::potential_query_instability)] let target = *vid_map.keys().next().unwrap();
let target = *vid_map.keys().next().expect("Keys somehow empty"); let deps = vid_map.swap_remove(&target).unwrap();
let deps = vid_map.remove(&target).expect("Entry somehow missing");
for smaller in deps.smaller.iter() { for smaller in deps.smaller.iter() {
for larger in deps.larger.iter() { for larger in deps.larger.iter() {
match (smaller, larger) { match (smaller, larger) {
(&RegionTarget::Region(_), &RegionTarget::Region(_)) => { (&RegionTarget::Region(_), &RegionTarget::Region(_)) => {
if let Entry::Occupied(v) = vid_map.entry(*smaller) { if let IndexEntry::Occupied(v) = vid_map.entry(*smaller) {
let smaller_deps = v.into_mut(); let smaller_deps = v.into_mut();
smaller_deps.larger.insert(*larger); smaller_deps.larger.insert(*larger);
// FIXME(#120456) - is `swap_remove` correct?
smaller_deps.larger.swap_remove(&target); smaller_deps.larger.swap_remove(&target);
} }
if let Entry::Occupied(v) = vid_map.entry(*larger) { if let IndexEntry::Occupied(v) = vid_map.entry(*larger) {
let larger_deps = v.into_mut(); let larger_deps = v.into_mut();
larger_deps.smaller.insert(*smaller); larger_deps.smaller.insert(*smaller);
// FIXME(#120456) - is `swap_remove` correct?
larger_deps.smaller.swap_remove(&target); larger_deps.smaller.swap_remove(&target);
} }
} }
@ -542,17 +525,15 @@ impl<'tcx> AutoTraitFinder<'tcx> {
// Do nothing; we don't care about regions that are smaller than vids. // Do nothing; we don't care about regions that are smaller than vids.
} }
(&RegionTarget::RegionVid(_), &RegionTarget::RegionVid(_)) => { (&RegionTarget::RegionVid(_), &RegionTarget::RegionVid(_)) => {
if let Entry::Occupied(v) = vid_map.entry(*smaller) { if let IndexEntry::Occupied(v) = vid_map.entry(*smaller) {
let smaller_deps = v.into_mut(); let smaller_deps = v.into_mut();
smaller_deps.larger.insert(*larger); smaller_deps.larger.insert(*larger);
// FIXME(#120456) - is `swap_remove` correct?
smaller_deps.larger.swap_remove(&target); smaller_deps.larger.swap_remove(&target);
} }
if let Entry::Occupied(v) = vid_map.entry(*larger) { if let IndexEntry::Occupied(v) = vid_map.entry(*larger) {
let larger_deps = v.into_mut(); let larger_deps = v.into_mut();
larger_deps.smaller.insert(*smaller); larger_deps.smaller.insert(*smaller);
// FIXME(#120456) - is `swap_remove` correct?
larger_deps.smaller.swap_remove(&target); larger_deps.smaller.swap_remove(&target);
} }
} }
@ -560,6 +541,7 @@ impl<'tcx> AutoTraitFinder<'tcx> {
} }
} }
} }
finished_map finished_map
} }
@ -588,7 +570,7 @@ impl<'tcx> AutoTraitFinder<'tcx> {
ty: Ty<'_>, ty: Ty<'_>,
nested: impl Iterator<Item = PredicateObligation<'tcx>>, nested: impl Iterator<Item = PredicateObligation<'tcx>>,
computed_preds: &mut FxIndexSet<ty::Predicate<'tcx>>, computed_preds: &mut FxIndexSet<ty::Predicate<'tcx>>,
fresh_preds: &mut FxHashSet<ty::Predicate<'tcx>>, fresh_preds: &mut FxIndexSet<ty::Predicate<'tcx>>,
predicates: &mut VecDeque<ty::PolyTraitPredicate<'tcx>>, predicates: &mut VecDeque<ty::PolyTraitPredicate<'tcx>>,
selcx: &mut SelectionContext<'_, 'tcx>, selcx: &mut SelectionContext<'_, 'tcx>,
) -> bool { ) -> bool {

852
src/librustdoc/clean/auto_trait.rs
View File

@ -1,95 +1,95 @@
use rustc_data_structures::fx::{FxIndexMap, FxIndexSet, IndexEntry};
use rustc_hir as hir; use rustc_hir as hir;
use rustc_hir::lang_items::LangItem; use rustc_infer::infer::region_constraints::{Constraint, RegionConstraintData};
use rustc_middle::ty::{Region, RegionVid, TypeFoldable}; use rustc_middle::bug;
use rustc_trait_selection::traits::auto_trait::{self, AutoTraitResult}; use rustc_middle::ty::{self, Region, Ty};
use rustc_span::def_id::DefId;
use rustc_span::symbol::{kw, Symbol};
use rustc_trait_selection::traits::auto_trait::{self, RegionTarget};
use std::fmt::Debug; use thin_vec::ThinVec;
use super::*; use crate::clean::{self, simplify, Lifetime};
use crate::clean::{
clean_generic_param_def, clean_middle_ty, clean_predicate, clean_trait_ref_with_bindings,
clean_ty_generics,
};
use crate::core::DocContext;
#[derive(Eq, PartialEq, Hash, Copy, Clone, Debug)] #[instrument(level = "debug", skip(cx))]
enum RegionTarget<'tcx> { pub(crate) fn synthesize_auto_trait_impls<'tcx>(
Region(Region<'tcx>), cx: &mut DocContext<'tcx>,
RegionVid(RegionVid), item_def_id: DefId,
} ) -> Vec<clean::Item> {
let tcx = cx.tcx;
let param_env = tcx.param_env(item_def_id);
let ty = tcx.type_of(item_def_id).instantiate_identity();
#[derive(Default, Debug, Clone)] let finder = auto_trait::AutoTraitFinder::new(tcx);
struct RegionDeps<'tcx> { let mut auto_trait_impls: Vec<_> = cx
larger: FxHashSet<RegionTarget<'tcx>>, .auto_traits
smaller: FxHashSet<RegionTarget<'tcx>>, .clone()
} .into_iter()
.filter_map(|trait_def_id| {
pub(crate) struct AutoTraitFinder<'a, 'tcx> { synthesize_auto_trait_impl(
pub(crate) cx: &'a mut core::DocContext<'tcx>, cx,
} ty,
trait_def_id,
impl<'a, 'tcx> AutoTraitFinder<'a, 'tcx> param_env,
where item_def_id,
'tcx: 'a, // should be an implied bound; rustc bug #98852. &finder,
{ DiscardPositiveImpls::No,
pub(crate) fn new(cx: &'a mut core::DocContext<'tcx>) -> Self { )
AutoTraitFinder { cx } })
.collect();
// We are only interested in case the type *doesn't* implement the `Sized` trait.
if !ty.is_sized(tcx, param_env)
&& let Some(sized_trait_def_id) = tcx.lang_items().sized_trait()
&& let Some(impl_item) = synthesize_auto_trait_impl(
cx,
ty,
sized_trait_def_id,
param_env,
item_def_id,
&finder,
DiscardPositiveImpls::Yes,
)
{
auto_trait_impls.push(impl_item);
} }
auto_trait_impls
}
fn generate_for_trait( #[instrument(level = "debug", skip(cx, finder))]
&mut self, fn synthesize_auto_trait_impl<'tcx>(
cx: &mut DocContext<'tcx>,
ty: Ty<'tcx>, ty: Ty<'tcx>,
trait_def_id: DefId, trait_def_id: DefId,
param_env: ty::ParamEnv<'tcx>, param_env: ty::ParamEnv<'tcx>,
item_def_id: DefId, item_def_id: DefId,
f: &auto_trait::AutoTraitFinder<'tcx>, finder: &auto_trait::AutoTraitFinder<'tcx>,
// If this is set, show only negative trait implementations, not positive ones. discard_positive_impls: DiscardPositiveImpls,
discard_positive_impl: bool, ) -> Option<clean::Item> {
) -> Option<Item> { let tcx = cx.tcx;
let tcx = self.cx.tcx;
let trait_ref = ty::Binder::dummy(ty::TraitRef::new(tcx, trait_def_id, [ty])); let trait_ref = ty::Binder::dummy(ty::TraitRef::new(tcx, trait_def_id, [ty]));
if !self.cx.generated_synthetics.insert((ty, trait_def_id)) { if !cx.generated_synthetics.insert((ty, trait_def_id)) {
debug!("get_auto_trait_impl_for({trait_ref:?}): already generated, aborting"); debug!("already generated, aborting");
return None; return None;
} }
let result = f.find_auto_trait_generics(ty, param_env, trait_def_id, |info| { let result = finder.find_auto_trait_generics(ty, param_env, trait_def_id, |info| {
let region_data = info.region_data; clean_param_env(cx, item_def_id, info.full_user_env, info.region_data, info.vid_to_region)
let names_map = tcx
.generics_of(item_def_id)
.params
.iter()
.filter_map(|param| match param.kind {
ty::GenericParamDefKind::Lifetime => Some(param.name),
_ => None,
})
.map(|name| (name, Lifetime(name)))
.collect();
let lifetime_predicates = Self::handle_lifetimes(&region_data, &names_map);
let new_generics = self.param_env_to_generics(
item_def_id,
info.full_user_env,
lifetime_predicates,
info.vid_to_region,
);
debug!(
"find_auto_trait_generics(item_def_id={:?}, trait_def_id={:?}): \
finished with {:?}",
item_def_id, trait_def_id, new_generics
);
new_generics
}); });
let polarity; let (generics, polarity) = match result {
let new_generics = match result { auto_trait::AutoTraitResult::PositiveImpl(generics) => {
AutoTraitResult::PositiveImpl(new_generics) => { if let DiscardPositiveImpls::Yes = discard_positive_impls {
polarity = ty::ImplPolarity::Positive;
if discard_positive_impl {
return None; return None;
} }
new_generics
}
AutoTraitResult::NegativeImpl => {
polarity = ty::ImplPolarity::Negative;
(generics, ty::ImplPolarity::Positive)
}
auto_trait::AutoTraitResult::NegativeImpl => {
// For negative impls, we use the generic params, but *not* the predicates, // For negative impls, we use the generic params, but *not* the predicates,
// from the original type. Otherwise, the displayed impl appears to be a // from the original type. Otherwise, the displayed impl appears to be a
// conditional negative impl, when it's really unconditional. // conditional negative impl, when it's really unconditional.
@ -102,124 +102,152 @@ where
// Instead, we generate `impl !Send for Foo<T>`, which better // Instead, we generate `impl !Send for Foo<T>`, which better
// expresses the fact that `Foo<T>` never implements `Send`, // expresses the fact that `Foo<T>` never implements `Send`,
// regardless of the choice of `T`. // regardless of the choice of `T`.
let raw_generics = clean_ty_generics( let mut generics = clean_ty_generics(
self.cx, cx,
tcx.generics_of(item_def_id), tcx.generics_of(item_def_id),
ty::GenericPredicates::default(), ty::GenericPredicates::default(),
); );
let params = raw_generics.params; generics.where_predicates.clear();
Generics { params, where_predicates: ThinVec::new() } (generics, ty::ImplPolarity::Negative)
} }
AutoTraitResult::ExplicitImpl => return None, auto_trait::AutoTraitResult::ExplicitImpl => return None,
}; };
Some(Item { Some(clean::Item {
name: None, name: None,
attrs: Default::default(), attrs: Default::default(),
item_id: ItemId::Auto { trait_: trait_def_id, for_: item_def_id }, item_id: clean::ItemId::Auto { trait_: trait_def_id, for_: item_def_id },
kind: Box::new(ImplItem(Box::new(Impl { kind: Box::new(clean::ImplItem(Box::new(clean::Impl {
unsafety: hir::Unsafety::Normal, unsafety: hir::Unsafety::Normal,
generics: new_generics, generics,
trait_: Some(clean_trait_ref_with_bindings(self.cx, trait_ref, ThinVec::new())), trait_: Some(clean_trait_ref_with_bindings(cx, trait_ref, ThinVec::new())),
for_: clean_middle_ty(ty::Binder::dummy(ty), self.cx, None, None), for_: clean_middle_ty(ty::Binder::dummy(ty), cx, None, None),
items: Vec::new(), items: Vec::new(),
polarity, polarity,
kind: ImplKind::Auto, kind: clean::ImplKind::Auto,
}))), }))),
cfg: None, cfg: None,
inline_stmt_id: None, inline_stmt_id: None,
}) })
}
#[derive(Debug)]
enum DiscardPositiveImpls {
Yes,
No,
}
#[instrument(level = "debug", skip(cx, region_data, vid_to_region))]
fn clean_param_env<'tcx>(
cx: &mut DocContext<'tcx>,
item_def_id: DefId,
param_env: ty::ParamEnv<'tcx>,
region_data: RegionConstraintData<'tcx>,
vid_to_region: FxIndexMap<ty::RegionVid, ty::Region<'tcx>>,
) -> clean::Generics {
let tcx = cx.tcx;
let generics = tcx.generics_of(item_def_id);
let params: ThinVec<_> = generics
.params
.iter()
.inspect(|param| {
if cfg!(debug_assertions) {
debug_assert!(!param.is_anonymous_lifetime() && !param.is_host_effect());
if let ty::GenericParamDefKind::Type { synthetic, .. } = param.kind {
debug_assert!(!synthetic && param.name != kw::SelfUpper);
}
} }
pub(crate) fn get_auto_trait_impls(&mut self, item_def_id: DefId) -> Vec<Item> {
let tcx = self.cx.tcx;
let param_env = tcx.param_env(item_def_id);
let ty = tcx.type_of(item_def_id).instantiate_identity();
let f = auto_trait::AutoTraitFinder::new(tcx);
debug!("get_auto_trait_impls({ty:?})");
let auto_traits: Vec<_> = self.cx.auto_traits.to_vec();
let mut auto_traits: Vec<Item> = auto_traits
.into_iter()
.filter_map(|trait_def_id| {
self.generate_for_trait(ty, trait_def_id, param_env, item_def_id, &f, false)
}) })
// We're basing the generics of the synthetic auto trait impl off of the generics of the
// implementing type. Its generic parameters may have defaults, don't copy them over:
// Generic parameter defaults are meaningless in impls.
.map(|param| clean_generic_param_def(param, clean::ParamDefaults::No, cx))
.collect(); .collect();
// We are only interested in case the type *doesn't* implement the Sized trait.
if !ty.is_sized(tcx, param_env) {
// In case `#![no_core]` is used, `sized_trait` returns nothing.
if let Some(item) = tcx.lang_items().sized_trait().and_then(|sized_trait_did| {
self.generate_for_trait(ty, sized_trait_did, param_env, item_def_id, &f, true)
}) {
auto_traits.push(item);
}
}
auto_traits
}
fn get_lifetime(region: Region<'_>, names_map: &FxHashMap<Symbol, Lifetime>) -> Lifetime { // FIXME(#111101): Incorporate the explicit predicates of the item here...
region_name(region) let item_predicates: FxIndexSet<_> =
.map(|name| { tcx.predicates_of(item_def_id).predicates.iter().map(|(pred, _)| pred).collect();
names_map let where_predicates = param_env
.get(&name) .caller_bounds()
.unwrap_or_else(|| panic!("Missing lifetime with name {name:?} for {region:?}")) .iter()
// FIXME: ...which hopefully allows us to simplify this:
.filter(|pred| {
!item_predicates.contains(pred)
|| pred
.as_trait_clause()
.is_some_and(|pred| tcx.lang_items().sized_trait() == Some(pred.def_id()))
}) })
.unwrap_or(&Lifetime::statik()) .map(|pred| {
.clone() tcx.fold_regions(pred, |r, _| match *r {
ty::ReVar(vid) => vid_to_region[&vid],
ty::ReEarlyParam(_) | ty::ReStatic | ty::ReBound(..) | ty::ReError(_) => r,
ty::ReLateParam(_) | ty::RePlaceholder(_) | ty::ReErased => {
bug!("unexpected region kind: {r:?}")
} }
})
})
.flat_map(|pred| clean_predicate(pred, cx))
.chain(clean_region_outlives_constraints(&region_data, generics))
.collect();
/// This method calculates two things: Lifetime constraints of the form `'a: 'b`, let mut generics = clean::Generics { params, where_predicates };
/// and region constraints of the form `RegionVid: 'a` simplify::sized_bounds(cx, &mut generics);
/// generics.where_predicates = simplify::where_clauses(cx, generics.where_predicates);
/// This is essentially a simplified version of lexical_region_resolve. However, generics
/// handle_lifetimes determines what *needs be* true in order for an impl to hold. }
/// lexical_region_resolve, along with much of the rest of the compiler, is concerned
/// with determining if a given set up constraints/predicates *are* met, given some
/// starting conditions (e.g., user-provided code). For this reason, it's easier
/// to perform the calculations we need on our own, rather than trying to make
/// existing inference/solver code do what we want.
fn handle_lifetimes<'cx>(
regions: &RegionConstraintData<'cx>,
names_map: &FxHashMap<Symbol, Lifetime>,
) -> ThinVec<WherePredicate> {
// Our goal is to 'flatten' the list of constraints by eliminating
// all intermediate RegionVids. At the end, all constraints should
// be between Regions (aka region variables). This gives us the information
// we need to create the Generics.
let mut finished: FxHashMap<_, Vec<_>> = Default::default();
let mut vid_map: FxHashMap<RegionTarget<'_>, RegionDeps<'_>> = Default::default(); /// Clean region outlives constraints to where-predicates.
///
/// This is essentially a simplified version of `lexical_region_resolve`.
///
/// However, here we determine what *needs to be* true in order for an impl to hold.
/// `lexical_region_resolve`, along with much of the rest of the compiler, is concerned
/// with determining if a given set up constraints / predicates *are* met, given some
/// starting conditions like user-provided code.
///
/// For this reason, it's easier to perform the calculations we need on our own,
/// rather than trying to make existing inference/solver code do what we want.
fn clean_region_outlives_constraints<'tcx>(
regions: &RegionConstraintData<'tcx>,
generics: &'tcx ty::Generics,
) -> ThinVec<clean::WherePredicate> {
// Our goal is to "flatten" the list of constraints by eliminating all intermediate
// `RegionVids` (region inference variables). At the end, all constraints should be
// between `Region`s. This gives us the information we need to create the where-predicates.
// This flattening is done in two parts.
// Flattening is done in two parts. First, we insert all of the constraints let mut outlives_predicates = FxIndexMap::<_, Vec<_>>::default();
// into a map. Each RegionTarget (either a RegionVid or a Region) maps let mut map = FxIndexMap::<RegionTarget<'_>, auto_trait::RegionDeps<'_>>::default();
// to its smaller and larger regions. Note that 'larger' regions correspond
// to sub-regions in Rust code (e.g., in 'a: 'b, 'a is the larger region). // (1) We insert all of the constraints into a map.
// Each `RegionTarget` (a `RegionVid` or a `Region`) maps to its smaller and larger regions.
// Note that "larger" regions correspond to sub regions in the surface language.
// E.g., in `'a: 'b`, `'a` is the larger region.
for (constraint, _) in &regions.constraints { for (constraint, _) in &regions.constraints {
match *constraint { match *constraint {
Constraint::VarSubVar(r1, r2) => { Constraint::VarSubVar(vid1, vid2) => {
{ let deps1 = map.entry(RegionTarget::RegionVid(vid1)).or_default();
let deps1 = vid_map.entry(RegionTarget::RegionVid(r1)).or_default(); deps1.larger.insert(RegionTarget::RegionVid(vid2));
deps1.larger.insert(RegionTarget::RegionVid(r2));
}
let deps2 = vid_map.entry(RegionTarget::RegionVid(r2)).or_default(); let deps2 = map.entry(RegionTarget::RegionVid(vid2)).or_default();
deps2.smaller.insert(RegionTarget::RegionVid(r1)); deps2.smaller.insert(RegionTarget::RegionVid(vid1));
} }
Constraint::RegSubVar(region, vid) => { Constraint::RegSubVar(region, vid) => {
let deps = vid_map.entry(RegionTarget::RegionVid(vid)).or_default(); let deps = map.entry(RegionTarget::RegionVid(vid)).or_default();
deps.smaller.insert(RegionTarget::Region(region)); deps.smaller.insert(RegionTarget::Region(region));
} }
Constraint::VarSubReg(vid, region) => { Constraint::VarSubReg(vid, region) => {
let deps = vid_map.entry(RegionTarget::RegionVid(vid)).or_default(); let deps = map.entry(RegionTarget::RegionVid(vid)).or_default();
deps.larger.insert(RegionTarget::Region(region)); deps.larger.insert(RegionTarget::Region(region));
} }
Constraint::RegSubReg(r1, r2) => { Constraint::RegSubReg(r1, r2) => {
// The constraint is already in the form that we want, so we're done with it // The constraint is already in the form that we want, so we're done with it
// Desired order is 'larger, smaller', so flip then // The desired order is [larger, smaller], so flip them.
if region_name(r1) != region_name(r2) { if early_bound_region_name(r1) != early_bound_region_name(r2) {
finished outlives_predicates
.entry(region_name(r2).expect("no region_name found")) .entry(early_bound_region_name(r2).expect("no region_name found"))
.or_default() .or_default()
.push(r1); .push(r1);
} }
@ -227,63 +255,63 @@ where
} }
} }
// Here, we 'flatten' the map one element at a time. // (2) Here, we "flatten" the map one element at a time. All of the elements' sub and super
// All of the element's sub and super regions are connected // regions are connected to each other. For example, if we have a graph that looks like this:
// to each other. For example, if we have a graph that looks like this:
// //
// (A, B) - C - (D, E) // (A, B) - C - (D, E)
// Where (A, B) are subregions, and (D,E) are super-regions
// //
// then after deleting 'C', the graph will look like this: // where (A, B) are sub regions, and (D,E) are super regions.
// ... - A - (D, E ...) // Then, after deleting 'C', the graph will look like this:
//
// ... - A - (D, E, ...)
// ... - B - (D, E, ...) // ... - B - (D, E, ...)
// (A, B, ...) - D - ... // (A, B, ...) - D - ...
// (A, B, ...) - E - ... // (A, B, ...) - E - ...
// //
// where '...' signifies the existing sub and super regions of an entry // where '...' signifies the existing sub and super regions of an entry. When two adjacent
// When two adjacent ty::Regions are encountered, we've computed a final // `Region`s are encountered, we've computed a final constraint, and add it to our list.
// constraint, and add it to our list. Since we make sure to never re-add // Since we make sure to never re-add deleted items, this process will always finish.
// deleted items, this process will always finish. while !map.is_empty() {
while !vid_map.is_empty() { let target = *map.keys().next().unwrap();
let target = *vid_map.keys().next().expect("Keys somehow empty"); let deps = map.swap_remove(&target).unwrap();
let deps = vid_map.remove(&target).expect("Entry somehow missing");
for smaller in deps.smaller.iter() { for smaller in &deps.smaller {
for larger in deps.larger.iter() { for larger in &deps.larger {
match (smaller, larger) { match (smaller, larger) {
(&RegionTarget::Region(r1), &RegionTarget::Region(r2)) => { (&RegionTarget::Region(smaller), &RegionTarget::Region(larger)) => {
if region_name(r1) != region_name(r2) { if early_bound_region_name(smaller) != early_bound_region_name(larger) {
finished outlives_predicates
.entry(region_name(r2).expect("no region name found")) .entry(
early_bound_region_name(larger).expect("no region name found"),
)
.or_default() .or_default()
.push(r1) // Larger, smaller .push(smaller)
} }
} }
(&RegionTarget::RegionVid(_), &RegionTarget::Region(_)) => { (&RegionTarget::RegionVid(_), &RegionTarget::Region(_)) => {
if let Entry::Occupied(v) = vid_map.entry(*smaller) { if let IndexEntry::Occupied(v) = map.entry(*smaller) {
let smaller_deps = v.into_mut(); let smaller_deps = v.into_mut();
smaller_deps.larger.insert(*larger); smaller_deps.larger.insert(*larger);
smaller_deps.larger.remove(&target); smaller_deps.larger.swap_remove(&target);
} }
} }
(&RegionTarget::Region(_), &RegionTarget::RegionVid(_)) => { (&RegionTarget::Region(_), &RegionTarget::RegionVid(_)) => {
if let Entry::Occupied(v) = vid_map.entry(*larger) { if let IndexEntry::Occupied(v) = map.entry(*larger) {
let deps = v.into_mut(); let deps = v.into_mut();
deps.smaller.insert(*smaller); deps.smaller.insert(*smaller);
deps.smaller.remove(&target); deps.smaller.swap_remove(&target);
} }
} }
(&RegionTarget::RegionVid(_), &RegionTarget::RegionVid(_)) => { (&RegionTarget::RegionVid(_), &RegionTarget::RegionVid(_)) => {
if let Entry::Occupied(v) = vid_map.entry(*smaller) { if let IndexEntry::Occupied(v) = map.entry(*smaller) {
let smaller_deps = v.into_mut(); let smaller_deps = v.into_mut();
smaller_deps.larger.insert(*larger); smaller_deps.larger.insert(*larger);
smaller_deps.larger.remove(&target); smaller_deps.larger.swap_remove(&target);
} }
if let IndexEntry::Occupied(v) = map.entry(*larger) {
if let Entry::Occupied(v) = vid_map.entry(*larger) {
let larger_deps = v.into_mut(); let larger_deps = v.into_mut();
larger_deps.smaller.insert(*smaller); larger_deps.smaller.insert(*smaller);
larger_deps.smaller.remove(&target); larger_deps.smaller.swap_remove(&target);
} }
} }
} }
@ -291,457 +319,43 @@ where
} }
} }
let lifetime_predicates = names_map let region_params: FxIndexSet<_> = generics
.params
.iter() .iter()
.flat_map(|(name, lifetime)| { .filter_map(|param| match param.kind {
let empty = Vec::new(); ty::GenericParamDefKind::Lifetime => Some(param.name),
let bounds: FxHashSet<GenericBound> = finished _ => None,
.get(name) })
.unwrap_or(&empty)
.iter()
.map(|region| GenericBound::Outlives(Self::get_lifetime(*region, names_map)))
.collect(); .collect();
region_params
.iter()
.filter_map(|&name| {
let bounds: FxIndexSet<_> = outlives_predicates
.get(&name)?
.iter()
.map(|&region| {
let lifetime = early_bound_region_name(region)
.inspect(|name| assert!(region_params.contains(name)))
.map(|name| Lifetime(name))
.unwrap_or(Lifetime::statik());
clean::GenericBound::Outlives(lifetime)
})
.collect();
if bounds.is_empty() { if bounds.is_empty() {
return None; return None;
} }
Some(WherePredicate::RegionPredicate { Some(clean::WherePredicate::RegionPredicate {
lifetime: lifetime.clone(), lifetime: Lifetime(name),
bounds: bounds.into_iter().collect(), bounds: bounds.into_iter().collect(),
}) })
}) })
.collect();
lifetime_predicates
}
fn extract_for_generics(&self, pred: ty::Clause<'tcx>) -> FxHashSet<GenericParamDef> {
let bound_predicate = pred.kind();
let tcx = self.cx.tcx;
let regions =
match bound_predicate.skip_binder() {
ty::ClauseKind::Trait(poly_trait_pred) => tcx
.collect_referenced_late_bound_regions(bound_predicate.rebind(poly_trait_pred)),
ty::ClauseKind::Projection(poly_proj_pred) => tcx
.collect_referenced_late_bound_regions(bound_predicate.rebind(poly_proj_pred)),
_ => return FxHashSet::default(),
};
regions
.into_iter()
.filter_map(|br| {
match br {
// We only care about named late bound regions, as we need to add them
// to the 'for<>' section
ty::BrNamed(def_id, name) => Some(GenericParamDef::lifetime(def_id, name)),
_ => None,
}
})
.collect() .collect()
}
fn make_final_bounds(
&self,
ty_to_bounds: FxHashMap<Type, FxHashSet<GenericBound>>,
ty_to_fn: FxHashMap<Type, (PolyTrait, Option<Type>)>,
lifetime_to_bounds: FxHashMap<Lifetime, FxHashSet<GenericBound>>,
) -> Vec<WherePredicate> {
ty_to_bounds
.into_iter()
.flat_map(|(ty, mut bounds)| {
if let Some((ref poly_trait, ref output)) = ty_to_fn.get(&ty) {
let mut new_path = poly_trait.trait_.clone();
let last_segment = new_path.segments.pop().expect("segments were empty");
let (old_input, old_output) = match last_segment.args {
GenericArgs::AngleBracketed { args, .. } => {
let types = args
.iter()
.filter_map(|arg| match arg {
GenericArg::Type(ty) => Some(ty.clone()),
_ => None,
})
.collect();
(types, None)
}
GenericArgs::Parenthesized { inputs, output } => (inputs, output),
};
let output = output.as_ref().cloned().map(Box::new);
if old_output.is_some() && old_output != output {
panic!("Output mismatch for {ty:?} {old_output:?} {output:?}");
}
let new_params = GenericArgs::Parenthesized { inputs: old_input, output };
new_path
.segments
.push(PathSegment { name: last_segment.name, args: new_params });
bounds.insert(GenericBound::TraitBound(
PolyTrait {
trait_: new_path,
generic_params: poly_trait.generic_params.clone(),
},
hir::TraitBoundModifier::None,
));
}
if bounds.is_empty() {
return None;
}
let mut bounds_vec = bounds.into_iter().collect();
self.sort_where_bounds(&mut bounds_vec);
Some(WherePredicate::BoundPredicate {
ty,
bounds: bounds_vec,
bound_params: Vec::new(),
})
})
.chain(lifetime_to_bounds.into_iter().filter(|(_, bounds)| !bounds.is_empty()).map(
|(lifetime, bounds)| {
let mut bounds_vec = bounds.into_iter().collect();
self.sort_where_bounds(&mut bounds_vec);
WherePredicate::RegionPredicate { lifetime, bounds: bounds_vec }
},
))
.collect()
}
/// Converts the calculated `ParamEnv` and lifetime information to a [`clean::Generics`](Generics), suitable for
/// display on the docs page. Cleaning the `Predicates` produces sub-optimal [`WherePredicate`]s,
/// so we fix them up:
///
/// * Multiple bounds for the same type are coalesced into one: e.g., `T: Copy`, `T: Debug`
/// becomes `T: Copy + Debug`
/// * `Fn` bounds are handled specially - instead of leaving it as `T: Fn(), <T as Fn::Output> =
/// K`, we use the dedicated syntax `T: Fn() -> K`
/// * We explicitly add a `?Sized` bound if we didn't find any `Sized` predicates for a type
fn param_env_to_generics(
&mut self,
item_def_id: DefId,
param_env: ty::ParamEnv<'tcx>,
mut existing_predicates: ThinVec<WherePredicate>,
vid_to_region: FxHashMap<ty::RegionVid, ty::Region<'tcx>>,
) -> Generics {
debug!(
"param_env_to_generics(item_def_id={:?}, param_env={:?}, \
existing_predicates={:?})",
item_def_id, param_env, existing_predicates
);
let tcx = self.cx.tcx;
// The `Sized` trait must be handled specially, since we only display it when
// it is *not* required (i.e., '?Sized')
let sized_trait = tcx.require_lang_item(LangItem::Sized, None);
let mut replacer = RegionReplacer { vid_to_region: &vid_to_region, tcx };
let orig_bounds: FxHashSet<_> = tcx.param_env(item_def_id).caller_bounds().iter().collect();
let clean_where_predicates = param_env
.caller_bounds()
.iter()
.filter(|p| {
!orig_bounds.contains(p)
|| match p.kind().skip_binder() {
ty::ClauseKind::Trait(pred) => pred.def_id() == sized_trait,
_ => false,
}
})
.map(|p| p.fold_with(&mut replacer));
let raw_generics = clean_ty_generics(
self.cx,
tcx.generics_of(item_def_id),
tcx.explicit_predicates_of(item_def_id),
);
let mut generic_params = raw_generics.params;
debug!("param_env_to_generics({item_def_id:?}): generic_params={generic_params:?}");
let mut has_sized = FxHashSet::default();
let mut ty_to_bounds: FxHashMap<_, FxHashSet<_>> = Default::default();
let mut lifetime_to_bounds: FxHashMap<_, FxHashSet<_>> = Default::default();
let mut ty_to_traits: FxHashMap<Type, FxHashSet<Path>> = Default::default();
let mut ty_to_fn: FxHashMap<Type, (PolyTrait, Option<Type>)> = Default::default();
// FIXME: This code shares much of the logic found in `clean_ty_generics` and
// `simplify::where_clause`. Consider deduplicating it to avoid diverging
// implementations.
// Further, the code below does not merge (partially re-sugared) bounds like
// `Tr<A = T>` & `Tr<B = U>` and it does not render higher-ranked parameters
// originating from equality predicates.
for p in clean_where_predicates {
let (orig_p, p) = (p, clean_predicate(p, self.cx));
if p.is_none() {
continue;
}
let p = p.unwrap();
match p {
WherePredicate::BoundPredicate { ty, mut bounds, .. } => {
// Writing a projection trait bound of the form
// <T as Trait>::Name : ?Sized
// is illegal, because ?Sized bounds can only
// be written in the (here, nonexistent) definition
// of the type.
// Therefore, we make sure that we never add a ?Sized
// bound for projections
if let Type::QPath { .. } = ty {
has_sized.insert(ty.clone());
}
if bounds.is_empty() {
continue;
}
let mut for_generics = self.extract_for_generics(orig_p);
assert!(bounds.len() == 1);
let mut b = bounds.pop().expect("bounds were empty");
if b.is_sized_bound(self.cx) {
has_sized.insert(ty.clone());
} else if !b
.get_trait_path()
.and_then(|trait_| {
ty_to_traits
.get(&ty)
.map(|bounds| bounds.contains(&strip_path_generics(trait_)))
})
.unwrap_or(false)
{
// If we've already added a projection bound for the same type, don't add
// this, as it would be a duplicate
// Handle any 'Fn/FnOnce/FnMut' bounds specially,
// as we want to combine them with any 'Output' qpaths
// later
let is_fn = match b {
GenericBound::TraitBound(ref mut p, _) => {
// Insert regions into the for_generics hash map first, to ensure
// that we don't end up with duplicate bounds (e.g., for<'b, 'b>)
for_generics.extend(p.generic_params.drain(..));
p.generic_params.extend(for_generics);
self.is_fn_trait(&p.trait_)
}
_ => false,
};
let poly_trait = b.get_poly_trait().expect("Cannot get poly trait");
if is_fn {
ty_to_fn
.entry(ty.clone())
.and_modify(|e| *e = (poly_trait.clone(), e.1.clone()))
.or_insert(((poly_trait.clone()), None));
ty_to_bounds.entry(ty.clone()).or_default();
} else {
ty_to_bounds.entry(ty.clone()).or_default().insert(b.clone());
}
}
}
WherePredicate::RegionPredicate { lifetime, bounds } => {
lifetime_to_bounds.entry(lifetime).or_default().extend(bounds);
}
WherePredicate::EqPredicate { lhs, rhs } => {
match lhs {
Type::QPath(box QPathData {
ref assoc,
ref self_type,
trait_: Some(ref trait_),
..
}) => {
let ty = &*self_type;
let mut new_trait = trait_.clone();
if self.is_fn_trait(trait_) && assoc.name == sym::Output {
ty_to_fn
.entry(ty.clone())
.and_modify(|e| {
*e = (e.0.clone(), Some(rhs.ty().unwrap().clone()))
})
.or_insert((
PolyTrait {
trait_: trait_.clone(),
generic_params: Vec::new(),
},
Some(rhs.ty().unwrap().clone()),
));
continue;
}
let args = &mut new_trait
.segments
.last_mut()
.expect("segments were empty")
.args;
match args {
// Convert something like '<T as Iterator::Item> = u8'
// to 'T: Iterator<Item=u8>'
GenericArgs::AngleBracketed { ref mut bindings, .. } => {
bindings.push(TypeBinding {
assoc: assoc.clone(),
kind: TypeBindingKind::Equality { term: rhs },
});
}
GenericArgs::Parenthesized { .. } => {
existing_predicates.push(WherePredicate::EqPredicate {
lhs: lhs.clone(),
rhs,
});
continue; // If something other than a Fn ends up
// with parentheses, leave it alone
}
}
let bounds = ty_to_bounds.entry(ty.clone()).or_default();
bounds.insert(GenericBound::TraitBound(
PolyTrait { trait_: new_trait, generic_params: Vec::new() },
hir::TraitBoundModifier::None,
));
// Remove any existing 'plain' bound (e.g., 'T: Iterator`) so
// that we don't see a
// duplicate bound like `T: Iterator + Iterator<Item=u8>`
// on the docs page.
bounds.remove(&GenericBound::TraitBound(
PolyTrait { trait_: trait_.clone(), generic_params: Vec::new() },
hir::TraitBoundModifier::None,
));
// Avoid creating any new duplicate bounds later in the outer
// loop
ty_to_traits.entry(ty.clone()).or_default().insert(trait_.clone());
}
_ => panic!("Unexpected LHS {lhs:?} for {item_def_id:?}"),
}
}
};
}
let final_bounds = self.make_final_bounds(ty_to_bounds, ty_to_fn, lifetime_to_bounds);
existing_predicates.extend(final_bounds);
for param in generic_params.iter_mut() {
match param.kind {
GenericParamDefKind::Type { ref mut default, ref mut bounds, .. } => {
// We never want something like `impl<T=Foo>`.
default.take();
let generic_ty = Type::Generic(param.name);
if !has_sized.contains(&generic_ty) {
bounds.insert(0, GenericBound::maybe_sized(self.cx));
}
}
GenericParamDefKind::Lifetime { .. } => {}
GenericParamDefKind::Const { ref mut default, .. } => {
// We never want something like `impl<const N: usize = 10>`
default.take();
}
}
}
self.sort_where_predicates(&mut existing_predicates);
Generics { params: generic_params, where_predicates: existing_predicates }
}
/// Ensure that the predicates are in a consistent order. The precise
/// ordering doesn't actually matter, but it's important that
/// a given set of predicates always appears in the same order -
/// both for visual consistency between 'rustdoc' runs, and to
/// make writing tests much easier
#[inline]
fn sort_where_predicates(&self, predicates: &mut [WherePredicate]) {
// We should never have identical bounds - and if we do,
// they're visually identical as well. Therefore, using
// an unstable sort is fine.
self.unstable_debug_sort(predicates);
}
/// Ensure that the bounds are in a consistent order. The precise
/// ordering doesn't actually matter, but it's important that
/// a given set of bounds always appears in the same order -
/// both for visual consistency between 'rustdoc' runs, and to
/// make writing tests much easier
#[inline]
fn sort_where_bounds(&self, bounds: &mut Vec<GenericBound>) {
// We should never have identical bounds - and if we do,
// they're visually identical as well. Therefore, using
// an unstable sort is fine.
self.unstable_debug_sort(bounds);
}
/// This might look horrendously hacky, but it's actually not that bad.
///
/// For performance reasons, we use several different FxHashMaps
/// in the process of computing the final set of where predicates.
/// However, the iteration order of a HashMap is completely unspecified.
/// In fact, the iteration of an FxHashMap can even vary between platforms,
/// since FxHasher has different behavior for 32-bit and 64-bit platforms.
///
/// Obviously, it's extremely undesirable for documentation rendering
/// to be dependent on the platform it's run on. Apart from being confusing
/// to end users, it makes writing tests much more difficult, as predicates
/// can appear in any order in the final result.
///
/// To solve this problem, we sort WherePredicates and GenericBounds
/// by their Debug string. The thing to keep in mind is that we don't really
/// care what the final order is - we're synthesizing an impl or bound
/// ourselves, so any order can be considered equally valid. By sorting the
/// predicates and bounds, however, we ensure that for a given codebase, all
/// auto-trait impls always render in exactly the same way.
///
/// Using the Debug implementation for sorting prevents us from needing to
/// write quite a bit of almost entirely useless code (e.g., how should two
/// Types be sorted relative to each other). It also allows us to solve the
/// problem for both WherePredicates and GenericBounds at the same time. This
/// approach is probably somewhat slower, but the small number of items
/// involved (impls rarely have more than a few bounds) means that it
/// shouldn't matter in practice.
fn unstable_debug_sort<T: Debug>(&self, vec: &mut [T]) {
vec.sort_by_cached_key(|x| format!("{x:?}"))
}
fn is_fn_trait(&self, path: &Path) -> bool {
let tcx = self.cx.tcx;
let did = path.def_id();
did == tcx.require_lang_item(LangItem::Fn, None)
|| did == tcx.require_lang_item(LangItem::FnMut, None)
|| did == tcx.require_lang_item(LangItem::FnOnce, None)
}
} }
fn region_name(region: Region<'_>) -> Option<Symbol> { fn early_bound_region_name(region: Region<'_>) -> Option<Symbol> {
match *region { match *region {
ty::ReEarlyParam(r) => Some(r.name), ty::ReEarlyParam(r) => Some(r.name),
_ => None, _ => None,
} }
} }
/// Replaces all [`ty::RegionVid`]s in a type with [`ty::Region`]s, using the provided map.
struct RegionReplacer<'a, 'tcx> {
vid_to_region: &'a FxHashMap<ty::RegionVid, ty::Region<'tcx>>,
tcx: TyCtxt<'tcx>,
}
impl<'a, 'tcx> TypeFolder<TyCtxt<'tcx>> for RegionReplacer<'a, 'tcx> {
fn interner(&self) -> TyCtxt<'tcx> {
self.tcx
}
fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
match *r {
// These are the regions that can be seen in the AST.
ty::ReVar(vid) => self.vid_to_region.get(&vid).cloned().unwrap_or(r),
ty::ReEarlyParam(_) | ty::ReStatic | ty::ReBound(..) | ty::ReError(_) => r,
r => bug!("unexpected region: {r:?}"),
}
}
}

109
src/librustdoc/clean/mod.rs
View File

@ -21,10 +21,8 @@ use rustc_hir::def::{CtorKind, DefKind, Res};
use rustc_hir::def_id::{DefId, DefIdMap, DefIdSet, LocalDefId, LOCAL_CRATE}; use rustc_hir::def_id::{DefId, DefIdMap, DefIdSet, LocalDefId, LOCAL_CRATE};
use rustc_hir::PredicateOrigin; use rustc_hir::PredicateOrigin;
use rustc_hir_analysis::lower_ty; use rustc_hir_analysis::lower_ty;
use rustc_infer::infer::region_constraints::{Constraint, RegionConstraintData};
use rustc_middle::metadata::Reexport; use rustc_middle::metadata::Reexport;
use rustc_middle::middle::resolve_bound_vars as rbv; use rustc_middle::middle::resolve_bound_vars as rbv;
use rustc_middle::ty::fold::TypeFolder;
use rustc_middle::ty::GenericArgsRef; use rustc_middle::ty::GenericArgsRef;
use rustc_middle::ty::TypeVisitableExt; use rustc_middle::ty::TypeVisitableExt;
use rustc_middle::ty::{self, AdtKind, Ty, TyCtxt}; use rustc_middle::ty::{self, AdtKind, Ty, TyCtxt};
@ -35,9 +33,7 @@ use rustc_span::{self, ExpnKind};
use rustc_trait_selection::traits::wf::object_region_bounds; use rustc_trait_selection::traits::wf::object_region_bounds;
use std::borrow::Cow; use std::borrow::Cow;
use std::collections::hash_map::Entry;
use std::collections::BTreeMap; use std::collections::BTreeMap;
use std::hash::Hash;
use std::mem; use std::mem;
use thin_vec::ThinVec; use thin_vec::ThinVec;
@ -502,6 +498,7 @@ fn projection_to_path_segment<'tcx>(
fn clean_generic_param_def<'tcx>( fn clean_generic_param_def<'tcx>(
def: &ty::GenericParamDef, def: &ty::GenericParamDef,
defaults: ParamDefaults,
cx: &mut DocContext<'tcx>, cx: &mut DocContext<'tcx>,
) -> GenericParamDef { ) -> GenericParamDef {
let (name, kind) = match def.kind { let (name, kind) = match def.kind {
@ -509,7 +506,9 @@ fn clean_generic_param_def<'tcx>(
(def.name, GenericParamDefKind::Lifetime { outlives: ThinVec::new() }) (def.name, GenericParamDefKind::Lifetime { outlives: ThinVec::new() })
} }
ty::GenericParamDefKind::Type { has_default, synthetic, .. } => { ty::GenericParamDefKind::Type { has_default, synthetic, .. } => {
let default = if has_default { let default = if let ParamDefaults::Yes = defaults
&& has_default
{
Some(clean_middle_ty( Some(clean_middle_ty(
ty::Binder::dummy(cx.tcx.type_of(def.def_id).instantiate_identity()), ty::Binder::dummy(cx.tcx.type_of(def.def_id).instantiate_identity()),
cx, cx,
@ -542,11 +541,14 @@ fn clean_generic_param_def<'tcx>(
Some(def.def_id), Some(def.def_id),
None, None,
)), )),
default: match has_default { default: if let ParamDefaults::Yes = defaults
true => Some(Box::new( && has_default
{
Some(Box::new(
cx.tcx.const_param_default(def.def_id).instantiate_identity().to_string(), cx.tcx.const_param_default(def.def_id).instantiate_identity().to_string(),
)), ))
false => None, } else {
None
}, },
is_host_effect, is_host_effect,
}, },
@ -556,6 +558,12 @@ fn clean_generic_param_def<'tcx>(
GenericParamDef { name, def_id: def.def_id, kind } GenericParamDef { name, def_id: def.def_id, kind }
} }
/// Whether to clean generic parameter defaults or not.
enum ParamDefaults {
Yes,
No,
}
fn clean_generic_param<'tcx>( fn clean_generic_param<'tcx>(
cx: &mut DocContext<'tcx>, cx: &mut DocContext<'tcx>,
generics: Option<&hir::Generics<'tcx>>, generics: Option<&hir::Generics<'tcx>>,
@ -759,34 +767,30 @@ fn clean_ty_generics<'tcx>(
gens: &ty::Generics, gens: &ty::Generics,
preds: ty::GenericPredicates<'tcx>, preds: ty::GenericPredicates<'tcx>,
) -> Generics { ) -> Generics {
// Don't populate `cx.impl_trait_bounds` before `clean`ning `where` clauses, // Don't populate `cx.impl_trait_bounds` before cleaning where clauses,
// since `Clean for ty::Predicate` would consume them. // since `clean_predicate` would consume them.
let mut impl_trait = BTreeMap::<u32, Vec<GenericBound>>::default(); let mut impl_trait = BTreeMap::<u32, Vec<GenericBound>>::default();
// Bounds in the type_params and lifetimes fields are repeated in the let params: ThinVec<_> = gens
// predicates field (see rustc_hir_analysis::collect::ty_generics), so remove
// them.
let stripped_params = gens
.params .params
.iter() .iter()
.filter_map(|param| match param.kind { .filter(|param| match param.kind {
ty::GenericParamDefKind::Lifetime if param.is_anonymous_lifetime() => None, ty::GenericParamDefKind::Lifetime => !param.is_anonymous_lifetime(),
ty::GenericParamDefKind::Lifetime => Some(clean_generic_param_def(param, cx)),
ty::GenericParamDefKind::Type { synthetic, .. } => { ty::GenericParamDefKind::Type { synthetic, .. } => {
if param.name == kw::SelfUpper { if param.name == kw::SelfUpper {
assert_eq!(param.index, 0); debug_assert_eq!(param.index, 0);
return None; return false;
} }
if synthetic { if synthetic {
impl_trait.insert(param.index, vec![]); impl_trait.insert(param.index, vec![]);
return None; return false;
} }
Some(clean_generic_param_def(param, cx)) true
} }
ty::GenericParamDefKind::Const { is_host_effect: true, .. } => None, ty::GenericParamDefKind::Const { is_host_effect, .. } => !is_host_effect,
ty::GenericParamDefKind::Const { .. } => Some(clean_generic_param_def(param, cx)),
}) })
.collect::<ThinVec<GenericParamDef>>(); .map(|param| clean_generic_param_def(param, ParamDefaults::Yes, cx))
.collect();
// param index -> [(trait DefId, associated type name & generics, term)] // param index -> [(trait DefId, associated type name & generics, term)]
let mut impl_trait_proj = let mut impl_trait_proj =
@ -882,56 +886,13 @@ fn clean_ty_generics<'tcx>(
// Now that `cx.impl_trait_bounds` is populated, we can process // Now that `cx.impl_trait_bounds` is populated, we can process
// remaining predicates which could contain `impl Trait`. // remaining predicates which could contain `impl Trait`.
let mut where_predicates = let where_predicates =
where_predicates.into_iter().flat_map(|p| clean_predicate(*p, cx)).collect::<Vec<_>>(); where_predicates.into_iter().flat_map(|p| clean_predicate(*p, cx)).collect();
// In the surface language, all type parameters except `Self` have an let mut generics = Generics { params, where_predicates };
// implicit `Sized` bound unless removed with `?Sized`. simplify::sized_bounds(cx, &mut generics);
// However, in the list of where-predicates below, `Sized` appears like a generics.where_predicates = simplify::where_clauses(cx, generics.where_predicates);
// normal bound: It's either present (the type is sized) or generics
// absent (the type might be unsized) but never *maybe* (i.e. `?Sized`).
//
// This is unsuitable for rendering.
// Thus, as a first step remove all `Sized` bounds that should be implicit.
//
// Note that associated types also have an implicit `Sized` bound but we
// don't actually know the set of associated types right here so that's
// handled when cleaning associated types.
let mut sized_params = FxHashSet::default();
where_predicates.retain(|pred| {
if let WherePredicate::BoundPredicate { ty: Generic(g), bounds, .. } = pred
&& *g != kw::SelfUpper
&& bounds.iter().any(|b| b.is_sized_bound(cx))
{
sized_params.insert(*g);
false
} else {
true
}
});
// As a final step, go through the type parameters again and insert a
// `?Sized` bound for each one we didn't find to be `Sized`.
for tp in &stripped_params {
if let types::GenericParamDefKind::Type { .. } = tp.kind
&& !sized_params.contains(&tp.name)
{
where_predicates.push(WherePredicate::BoundPredicate {
ty: Type::Generic(tp.name),
bounds: vec![GenericBound::maybe_sized(cx)],
bound_params: Vec::new(),
})
}
}
// It would be nice to collect all of the bounds on a type and recombine
// them if possible, to avoid e.g., `where T: Foo, T: Bar, T: Sized, T: 'a`
// and instead see `where T: Foo + Bar + Sized + 'a`
Generics {
params: stripped_params,
where_predicates: simplify::where_clauses(cx, where_predicates),
}
} }
fn clean_ty_alias_inner_type<'tcx>( fn clean_ty_alias_inner_type<'tcx>(

45
src/librustdoc/clean/simplify.rs
View File

@ -12,6 +12,7 @@
//! bounds by special casing scenarios such as these. Fun! //! bounds by special casing scenarios such as these. Fun!
use rustc_data_structures::fx::FxIndexMap; use rustc_data_structures::fx::FxIndexMap;
use rustc_data_structures::unord::UnordSet;
use rustc_hir::def_id::DefId; use rustc_hir::def_id::DefId;
use rustc_middle::ty; use rustc_middle::ty;
use thin_vec::ThinVec; use thin_vec::ThinVec;
@ -21,7 +22,7 @@ use crate::clean::GenericArgs as PP;
use crate::clean::WherePredicate as WP; use crate::clean::WherePredicate as WP;
use crate::core::DocContext; use crate::core::DocContext;
pub(crate) fn where_clauses(cx: &DocContext<'_>, clauses: Vec<WP>) -> ThinVec<WP> { pub(crate) fn where_clauses(cx: &DocContext<'_>, clauses: ThinVec<WP>) -> ThinVec<WP> {
// First, partition the where clause into its separate components. // First, partition the where clause into its separate components.
// //
// We use `FxIndexMap` so that the insertion order is preserved to prevent messing up to // We use `FxIndexMap` so that the insertion order is preserved to prevent messing up to
@ -128,6 +129,48 @@ fn trait_is_same_or_supertrait(cx: &DocContext<'_>, child: DefId, trait_: DefId)
.any(|did| trait_is_same_or_supertrait(cx, did, trait_)) .any(|did| trait_is_same_or_supertrait(cx, did, trait_))
} }
pub(crate) fn sized_bounds(cx: &mut DocContext<'_>, generics: &mut clean::Generics) {
let mut sized_params = UnordSet::new();
// In the surface language, all type parameters except `Self` have an
// implicit `Sized` bound unless removed with `?Sized`.
// However, in the list of where-predicates below, `Sized` appears like a
// normal bound: It's either present (the type is sized) or
// absent (the type might be unsized) but never *maybe* (i.e. `?Sized`).
//
// This is unsuitable for rendering.
// Thus, as a first step remove all `Sized` bounds that should be implicit.
//
// Note that associated types also have an implicit `Sized` bound but we
// don't actually know the set of associated types right here so that
// should be handled when cleaning associated types.
generics.where_predicates.retain(|pred| {
if let WP::BoundPredicate { ty: clean::Generic(param), bounds, .. } = pred
&& *param != rustc_span::symbol::kw::SelfUpper
&& bounds.iter().any(|b| b.is_sized_bound(cx))
{
sized_params.insert(*param);
false
} else {
true
}
});
// As a final step, go through the type parameters again and insert a
// `?Sized` bound for each one we didn't find to be `Sized`.
for param in &generics.params {
if let clean::GenericParamDefKind::Type { .. } = param.kind
&& !sized_params.contains(&param.name)
{
generics.where_predicates.push(WP::BoundPredicate {
ty: clean::Type::Generic(param.name),
bounds: vec![clean::GenericBound::maybe_sized(cx)],
bound_params: Vec::new(),
})
}
}
}
/// Move bounds that are (likely) directly attached to generic parameters from the where-clause to /// Move bounds that are (likely) directly attached to generic parameters from the where-clause to
/// the respective parameter. /// the respective parameter.
/// ///

7
src/librustdoc/clean/types.rs
View File

@ -1277,13 +1277,6 @@ impl GenericBound {
false false
} }
pub(crate) fn get_poly_trait(&self) -> Option<PolyTrait> {
if let GenericBound::TraitBound(ref p, _) = *self {
return Some(p.clone());
}
None
}
pub(crate) fn get_trait_path(&self) -> Option<Path> { pub(crate) fn get_trait_path(&self) -> Option<Path> {
if let GenericBound::TraitBound(PolyTrait { ref trait_, .. }, _) = *self { if let GenericBound::TraitBound(PolyTrait { ref trait_, .. }, _) = *self {
Some(trait_.clone()) Some(trait_.clone())

16
src/librustdoc/clean/utils.rs
View File

@ -1,4 +1,4 @@
use crate::clean::auto_trait::AutoTraitFinder; use crate::clean::auto_trait::synthesize_auto_trait_impls;
use crate::clean::blanket_impl::BlanketImplFinder; use crate::clean::blanket_impl::BlanketImplFinder;
use crate::clean::render_macro_matchers::render_macro_matcher; use crate::clean::render_macro_matchers::render_macro_matcher;
use crate::clean::{ use crate::clean::{
@ -251,15 +251,6 @@ pub(super) fn clean_middle_path<'tcx>(
} }
} }
/// Remove the generic arguments from a path.
pub(crate) fn strip_path_generics(mut path: Path) -> Path {
for ps in path.segments.iter_mut() {
ps.args = GenericArgs::AngleBracketed { args: Default::default(), bindings: ThinVec::new() }
}
path
}
pub(crate) fn qpath_to_string(p: &hir::QPath<'_>) -> String { pub(crate) fn qpath_to_string(p: &hir::QPath<'_>) -> String {
let segments = match *p { let segments = match *p {
hir::QPath::Resolved(_, path) => &path.segments, hir::QPath::Resolved(_, path) => &path.segments,
@ -486,6 +477,7 @@ pub(crate) fn resolve_type(cx: &mut DocContext<'_>, path: Path) -> Type {
} }
} }
// FIXME(fmease): Update the `get_*` terminology to the `synthesize_` one.
pub(crate) fn get_auto_trait_and_blanket_impls( pub(crate) fn get_auto_trait_and_blanket_impls(
cx: &mut DocContext<'_>, cx: &mut DocContext<'_>,
item_def_id: DefId, item_def_id: DefId,
@ -493,8 +485,8 @@ pub(crate) fn get_auto_trait_and_blanket_impls(
let auto_impls = cx let auto_impls = cx
.sess() .sess()
.prof .prof
.generic_activity("get_auto_trait_impls") .generic_activity("synthesize_auto_trait_impls")
.run(|| AutoTraitFinder::new(cx).get_auto_trait_impls(item_def_id)); .run(|| synthesize_auto_trait_impls(cx, item_def_id));
let blanket_impls = cx let blanket_impls = cx
.sess() .sess()
.prof .prof

21
tests/rustdoc/synthetic_auto/bounds.rs Normal file
View File

@ -0,0 +1,21 @@
pub struct Outer<T>(Inner<T>);
pub struct Inner<T>(T);
// @has bounds/struct.Outer.html
// @has - '//*[@id="synthetic-implementations-list"]//*[@class="impl"]//h3[@class="code-header"]' \
// "impl<T> Unpin for Outer<T>where \
// T: for<'any> Trait<A = (), B<'any> = (), X = ()>,"
impl<T> std::marker::Unpin for Inner<T>
where
T: for<'any> Trait<A = (), B<'any> = (), X = ()>,
{}
pub trait Trait: SuperTrait {
type A;
type B<'a>;
}
pub trait SuperTrait {
type X;
}

4
tests/rustdoc/synthetic_auto/complex.rs
View File

@ -21,8 +21,8 @@ mod foo {
// @has complex/struct.NotOuter.html // @has complex/struct.NotOuter.html
// @has - '//*[@id="synthetic-implementations-list"]//*[@class="impl"]//h3[@class="code-header"]' \ // @has - '//*[@id="synthetic-implementations-list"]//*[@class="impl"]//h3[@class="code-header"]' \
// "impl<'a, T, K: ?Sized> Send for Outer<'a, T, K>where K: for<'b> Fn((&'b bool, &'a u8)) \ // "impl<'a, T, K> Send for Outer<'a, T, K>where 'a: 'static, T: MyTrait<'a>, \
// -> &'b i8, T: MyTrait<'a>, <T as MyTrait<'a>>::MyItem: Copy, 'a: 'static" // K: for<'b> Fn((&'b bool, &'a u8)) -> &'b i8 + ?Sized, <T as MyTrait<'a>>::MyItem: Copy,"
pub use foo::{Foo, Inner as NotInner, MyTrait as NotMyTrait, Outer as NotOuter}; pub use foo::{Foo, Inner as NotInner, MyTrait as NotMyTrait, Outer as NotOuter};

2
tests/rustdoc/synthetic_auto/lifetimes.rs
View File

@ -10,7 +10,7 @@ where
// @has lifetimes/struct.Foo.html // @has lifetimes/struct.Foo.html
// @has - '//*[@id="synthetic-implementations-list"]//*[@class="impl"]//h3[@class="code-header"]' \ // @has - '//*[@id="synthetic-implementations-list"]//*[@class="impl"]//h3[@class="code-header"]' \
// "impl<'c, K> Send for Foo<'c, K>where K: for<'b> Fn(&'b bool) -> &'c u8, 'c: 'static" // "impl<'c, K> Send for Foo<'c, K>where 'c: 'static, K: for<'b> Fn(&'b bool) -> &'c u8,"
// //
// @has - '//*[@id="synthetic-implementations-list"]//*[@class="impl"]//h3[@class="code-header"]' \ // @has - '//*[@id="synthetic-implementations-list"]//*[@class="impl"]//h3[@class="code-header"]' \
// "impl<'c, K> Sync for Foo<'c, K>where K: Sync" // "impl<'c, K> Sync for Foo<'c, K>where K: Sync"

5
tests/rustdoc/synthetic_auto/no-redundancy.rs
View File

@ -1,6 +1,3 @@
// FIXME(fmease, #119216): Reenable this test!
//@ ignore-test
pub struct Inner<T> { pub struct Inner<T> {
field: T, field: T,
} }
@ -13,7 +10,7 @@ where
// @has no_redundancy/struct.Outer.html // @has no_redundancy/struct.Outer.html
// @has - '//*[@id="synthetic-implementations-list"]//*[@class="impl"]//h3[@class="code-header"]' \ // @has - '//*[@id="synthetic-implementations-list"]//*[@class="impl"]//h3[@class="code-header"]' \
// "impl<T> Send for Outer<T>where T: Send + Copy" // "impl<T> Send for Outer<T>where T: Copy + Send"
pub struct Outer<T> { pub struct Outer<T> {
inner_field: Inner<T>, inner_field: Inner<T>,
} }

6
tests/rustdoc/synthetic_auto/project.rs
View File

@ -24,11 +24,11 @@ where
// @has project/struct.Foo.html // @has project/struct.Foo.html
// @has - '//*[@id="synthetic-implementations-list"]//*[@class="impl"]//h3[@class="code-header"]' \ // @has - '//*[@id="synthetic-implementations-list"]//*[@class="impl"]//h3[@class="code-header"]' \
// "impl<'c, K> Send for Foo<'c, K>where K: MyTrait<MyItem = bool>, 'c: 'static" // "impl<'c, K> Send for Foo<'c, K>where 'c: 'static, K: MyTrait<MyItem = bool>,"
// //
// @has - '//*[@id="synthetic-implementations-list"]//*[@class="impl"]//h3[@class="code-header"]' \ // @has - '//*[@id="synthetic-implementations-list"]//*[@class="impl"]//h3[@class="code-header"]' \
// "impl<'c, K> Sync for Foo<'c, K>where K: MyTrait, <K as MyTrait>::MyItem: OtherTrait, \ // "impl<'c, K> Sync for Foo<'c, K>where 'c: 'static, K: MyTrait, \
// 'c: 'static," // <K as MyTrait>::MyItem: OtherTrait,"
pub struct Foo<'c, K: 'c> { pub struct Foo<'c, K: 'c> {
inner_field: Inner<'c, K>, inner_field: Inner<'c, K>,
} }