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rustdoc: heavily simplify synthesis of auto trait impls

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This commit is contained in:
León Orell Valerian Liehr 2024-03-31 20:37:35 +02:00
parent cbd593ed18
commit 069e7f2a76
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GPG Key ID: D17A07215F68E713
8 changed files with 456 additions and 759 deletions
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15
compiler/rustc_trait_selection/src/traits/auto_trait.rs
View File

@ -25,8 +25,8 @@ pub enum RegionTarget<'tcx> {
#[derive(Default, Debug, Clone)]
pub struct RegionDeps<'tcx> {
larger: FxIndexSet<RegionTarget<'tcx>>,
smaller: FxIndexSet<RegionTarget<'tcx>>,
pub larger: FxIndexSet<RegionTarget<'tcx>>,
pub smaller: FxIndexSet<RegionTarget<'tcx>>,
}
pub enum AutoTraitResult<A> {
@ -81,19 +81,12 @@ impl<'tcx> AutoTraitFinder<'tcx> {
let infcx = tcx.infer_ctxt().build();
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(
tcx,
ObligationCause::dummy(),
orig_env,
ty::TraitPredicate {
trait_ref,
polarity: if polarity {
ty::PredicatePolarity::Positive
} else {
ty::PredicatePolarity::Negative
},
},
ty::TraitPredicate { trait_ref, polarity },
));
if let Ok(Some(ImplSource::UserDefined(_))) = result {
debug!(

761
src/librustdoc/clean/auto_trait.rs
View File

@ -1,92 +1,95 @@
use rustc_data_structures::fx::{FxIndexMap, FxIndexSet, IndexEntry};
use rustc_hir as hir;
use rustc_hir::lang_items::LangItem;
use rustc_middle::ty::{Region, RegionVid, TypeFoldable};
use rustc_trait_selection::traits::auto_trait::{self, AutoTraitResult};
use rustc_infer::infer::region_constraints::{Constraint, RegionConstraintData};
use rustc_middle::bug;
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)]
enum RegionTarget<'tcx> {
Region(Region<'tcx>),
RegionVid(RegionVid),
}
#[instrument(level = "debug", skip(cx))]
pub(crate) fn synthesize_auto_trait_impls<'tcx>(
cx: &mut DocContext<'tcx>,
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)]
struct RegionDeps<'tcx> {
larger: FxIndexSet<RegionTarget<'tcx>>,
smaller: FxIndexSet<RegionTarget<'tcx>>,
}
pub(crate) struct AutoTraitFinder<'a, 'tcx> {
pub(crate) cx: &'a mut core::DocContext<'tcx>,
}
impl<'a, 'tcx> AutoTraitFinder<'a, 'tcx> {
pub(crate) fn new(cx: &'a mut core::DocContext<'tcx>) -> Self {
AutoTraitFinder { cx }
let finder = auto_trait::AutoTraitFinder::new(tcx);
let mut auto_trait_impls: Vec<_> = cx
.auto_traits
.clone()
.into_iter()
.filter_map(|trait_def_id| {
synthesize_auto_trait_impl(
cx,
ty,
trait_def_id,
param_env,
item_def_id,
&finder,
DiscardPositiveImpls::No,
)
})
.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(
&mut self,
#[instrument(level = "debug", skip(cx, finder))]
fn synthesize_auto_trait_impl<'tcx>(
cx: &mut DocContext<'tcx>,
ty: Ty<'tcx>,
trait_def_id: DefId,
param_env: ty::ParamEnv<'tcx>,
item_def_id: DefId,
f: &auto_trait::AutoTraitFinder<'tcx>,
// If this is set, show only negative trait implementations, not positive ones.
discard_positive_impl: bool,
) -> Option<Item> {
let tcx = self.cx.tcx;
finder: &auto_trait::AutoTraitFinder<'tcx>,
discard_positive_impls: DiscardPositiveImpls,
) -> Option<clean::Item> {
let tcx = cx.tcx;
let trait_ref = ty::Binder::dummy(ty::TraitRef::new(tcx, trait_def_id, [ty]));
if !self.cx.generated_synthetics.insert((ty, trait_def_id)) {
debug!("get_auto_trait_impl_for({trait_ref:?}): already generated, aborting");
if !cx.generated_synthetics.insert((ty, trait_def_id)) {
debug!("already generated, aborting");
return None;
}
let result = f.find_auto_trait_generics(ty, param_env, trait_def_id, |info| {
let region_data = info.region_data;
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 result = finder.find_auto_trait_generics(ty, param_env, trait_def_id, |info| {
clean_param_env(cx, item_def_id, info.full_user_env, info.region_data, info.vid_to_region)
});
let polarity;
let new_generics = match result {
AutoTraitResult::PositiveImpl(new_generics) => {
polarity = ty::ImplPolarity::Positive;
if discard_positive_impl {
let (generics, polarity) = match result {
auto_trait::AutoTraitResult::PositiveImpl(generics) => {
if let DiscardPositiveImpls::Yes = discard_positive_impls {
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,
// from the original type. Otherwise, the displayed impl appears to be a
// conditional negative impl, when it's really unconditional.
@ -99,124 +102,152 @@ impl<'a, 'tcx> AutoTraitFinder<'a, 'tcx> {
// Instead, we generate `impl !Send for Foo<T>`, which better
// expresses the fact that `Foo<T>` never implements `Send`,
// regardless of the choice of `T`.
let raw_generics = clean_ty_generics(
self.cx,
let mut generics = clean_ty_generics(
cx,
tcx.generics_of(item_def_id),
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,
attrs: Default::default(),
item_id: ItemId::Auto { trait_: trait_def_id, for_: item_def_id },
kind: Box::new(ImplItem(Box::new(Impl {
item_id: clean::ItemId::Auto { trait_: trait_def_id, for_: item_def_id },
kind: Box::new(clean::ImplItem(Box::new(clean::Impl {
unsafety: hir::Unsafety::Normal,
generics: new_generics,
trait_: Some(clean_trait_ref_with_bindings(self.cx, trait_ref, ThinVec::new())),
for_: clean_middle_ty(ty::Binder::dummy(ty), self.cx, None, None),
generics,
trait_: Some(clean_trait_ref_with_bindings(cx, trait_ref, ThinVec::new())),
for_: clean_middle_ty(ty::Binder::dummy(ty), cx, None, None),
items: Vec::new(),
polarity,
kind: ImplKind::Auto,
kind: clean::ImplKind::Auto,
}))),
cfg: 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();
// 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: &FxIndexMap<Symbol, Lifetime>) -> Lifetime {
region_name(region)
.map(|name| {
names_map
.get(&name)
.unwrap_or_else(|| panic!("Missing lifetime with name {name:?} for {region:?}"))
// FIXME(#111101): Incorporate the explicit predicates of the item here...
let item_predicates: FxIndexSet<_> =
tcx.predicates_of(item_def_id).predicates.iter().map(|(pred, _)| pred).collect();
let where_predicates = param_env
.caller_bounds()
.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())
.clone()
.map(|pred| {
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`,
/// and region constraints of the form `RegionVid: 'a`
///
/// This is essentially a simplified version of lexical_region_resolve. However,
/// 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: &FxIndexMap<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: FxIndexMap<_, Vec<_>> = Default::default();
let mut generics = clean::Generics { params, where_predicates };
simplify::sized_bounds(cx, &mut generics);
generics.where_predicates = simplify::where_clauses(cx, generics.where_predicates);
generics
}
let mut vid_map: FxIndexMap<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
// into a map. Each RegionTarget (either a RegionVid or a Region) maps
// 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).
let mut outlives_predicates = FxIndexMap::<_, Vec<_>>::default();
let mut map = FxIndexMap::<RegionTarget<'_>, auto_trait::RegionDeps<'_>>::default();
// (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 {
match *constraint {
Constraint::VarSubVar(r1, r2) => {
{
let deps1 = vid_map.entry(RegionTarget::RegionVid(r1)).or_default();
deps1.larger.insert(RegionTarget::RegionVid(r2));
}
Constraint::VarSubVar(vid1, vid2) => {
let deps1 = map.entry(RegionTarget::RegionVid(vid1)).or_default();
deps1.larger.insert(RegionTarget::RegionVid(vid2));
let deps2 = vid_map.entry(RegionTarget::RegionVid(r2)).or_default();
deps2.smaller.insert(RegionTarget::RegionVid(r1));
let deps2 = map.entry(RegionTarget::RegionVid(vid2)).or_default();
deps2.smaller.insert(RegionTarget::RegionVid(vid1));
}
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));
}
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));
}
Constraint::RegSubReg(r1, r2) => {
// The constraint is already in the form that we want, so we're done with it
// Desired order is 'larger, smaller', so flip then
if region_name(r1) != region_name(r2) {
finished
.entry(region_name(r2).expect("no region_name found"))
// The desired order is [larger, smaller], so flip them.
if early_bound_region_name(r1) != early_bound_region_name(r2) {
outlives_predicates
.entry(early_bound_region_name(r2).expect("no region_name found"))
.or_default()
.push(r1);
}
@ -224,60 +255,60 @@ impl<'a, 'tcx> AutoTraitFinder<'a, 'tcx> {
}
}
// Here, we 'flatten' the map one element at a time.
// All of the element's sub and super regions are connected
// to each other. For example, if we have a graph that looks like this:
// (2) Here, we "flatten" the map one element at a time. All of the elements' sub and super
// regions are connected to each other. For example, if we have a graph that looks like this:
//
// (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:
// ... - A - (D, E ...)
// where (A, B) are sub regions, and (D,E) are super regions.
// Then, after deleting 'C', the graph will look like this:
//
// ... - A - (D, E, ...)
// ... - B - (D, E, ...)
// (A, B, ...) - D - ...
// (A, B, ...) - E - ...
//
// where '...' signifies the existing sub and super regions of an entry
// When two adjacent ty::Regions are encountered, we've computed a final
// constraint, and add it to our list. Since we make sure to never re-add
// deleted items, this process will always finish.
while !vid_map.is_empty() {
let target = *vid_map.keys().next().unwrap();
let deps = vid_map.swap_remove(&target).unwrap();
// where '...' signifies the existing sub and super regions of an entry. When two adjacent
// `Region`s are encountered, we've computed a final constraint, and add it to our list.
// Since we make sure to never re-add deleted items, this process will always finish.
while !map.is_empty() {
let target = *map.keys().next().unwrap();
let deps = map.swap_remove(&target).unwrap();
for smaller in deps.smaller.iter() {
for larger in deps.larger.iter() {
for smaller in &deps.smaller {
for larger in &deps.larger {
match (smaller, larger) {
(&RegionTarget::Region(r1), &RegionTarget::Region(r2)) => {
if region_name(r1) != region_name(r2) {
finished
.entry(region_name(r2).expect("no region name found"))
(&RegionTarget::Region(smaller), &RegionTarget::Region(larger)) => {
if early_bound_region_name(smaller) != early_bound_region_name(larger) {
outlives_predicates
.entry(
early_bound_region_name(larger).expect("no region name found"),
)
.or_default()
.push(r1) // Larger, smaller
.push(smaller)
}
}
(&RegionTarget::RegionVid(_), &RegionTarget::Region(_)) => {
if let IndexEntry::Occupied(v) = vid_map.entry(*smaller) {
if let IndexEntry::Occupied(v) = map.entry(*smaller) {
let smaller_deps = v.into_mut();
smaller_deps.larger.insert(*larger);
smaller_deps.larger.swap_remove(&target);
}
}
(&RegionTarget::Region(_), &RegionTarget::RegionVid(_)) => {
if let IndexEntry::Occupied(v) = vid_map.entry(*larger) {
if let IndexEntry::Occupied(v) = map.entry(*larger) {
let deps = v.into_mut();
deps.smaller.insert(*smaller);
deps.smaller.swap_remove(&target);
}
}
(&RegionTarget::RegionVid(_), &RegionTarget::RegionVid(_)) => {
if let IndexEntry::Occupied(v) = vid_map.entry(*smaller) {
if let IndexEntry::Occupied(v) = map.entry(*smaller) {
let smaller_deps = v.into_mut();
smaller_deps.larger.insert(*larger);
smaller_deps.larger.swap_remove(&target);
}
if let IndexEntry::Occupied(v) = vid_map.entry(*larger) {
if let IndexEntry::Occupied(v) = map.entry(*larger) {
let larger_deps = v.into_mut();
larger_deps.smaller.insert(*smaller);
larger_deps.smaller.swap_remove(&target);
@ -288,381 +319,43 @@ impl<'a, 'tcx> AutoTraitFinder<'a, 'tcx> {
}
}
let lifetime_predicates = names_map
let region_params: FxIndexSet<_> = generics
.params
.iter()
.flat_map(|(name, lifetime)| {
let empty = Vec::new();
let bounds: FxIndexSet<GenericBound> = finished
.get(name)
.unwrap_or(&empty)
.iter()
.map(|region| GenericBound::Outlives(Self::get_lifetime(*region, names_map)))
.collect();
if bounds.is_empty() {
return None;
}
Some(WherePredicate::RegionPredicate {
lifetime: lifetime.clone(),
bounds: bounds.into_iter().collect(),
})
})
.collect();
lifetime_predicates
}
fn extract_for_generics(&self, pred: ty::Clause<'tcx>) -> FxIndexSet<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 FxIndexSet::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()
}
fn make_final_bounds(
&self,
ty_to_bounds: FxIndexMap<Type, FxIndexSet<GenericBound>>,
ty_to_fn: FxIndexMap<Type, (PolyTrait, Option<Type>)>,
lifetime_to_bounds: FxIndexMap<Lifetime, FxIndexSet<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()),
.filter_map(|param| match param.kind {
ty::GenericParamDefKind::Lifetime => Some(param.name),
_ => 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,
));
}
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() {
return None;
}
Some(WherePredicate::BoundPredicate {
ty,
Some(clean::WherePredicate::RegionPredicate {
lifetime: Lifetime(name),
bounds: bounds.into_iter().collect(),
bound_params: Vec::new(),
})
})
.chain(lifetime_to_bounds.into_iter().filter(|(_, bounds)| !bounds.is_empty()).map(
|(lifetime, bounds)| WherePredicate::RegionPredicate {
lifetime,
bounds: bounds.into_iter().collect(),
},
))
.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
#[instrument(level = "debug", skip(self, vid_to_region))]
fn param_env_to_generics(
&mut self,
item_def_id: DefId,
param_env: ty::ParamEnv<'tcx>,
mut existing_predicates: ThinVec<WherePredicate>,
vid_to_region: FxIndexMap<ty::RegionVid, ty::Region<'tcx>>,
) -> Generics {
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 };
// FIXME(fmease): Remove this!
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(); // NOTE(fmease): not used for iteration
let mut ty_to_bounds = FxIndexMap::<_, FxIndexSet<_>>::default();
let mut lifetime_to_bounds = FxIndexMap::<_, FxIndexSet<_>>::default();
let mut ty_to_traits = FxIndexMap::<Type, FxIndexSet<Path>>::default();
let mut ty_to_fn = FxIndexMap::<Type, (PolyTrait, Option<Type>)>::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);
tcx.is_fn_trait(p.trait_.def_id())
}
_ => 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 tcx.is_fn_trait(trait_.def_id()) && 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.swap_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();
}
}
}
Generics { params: generic_params, where_predicates: existing_predicates }
}
}
fn region_name(region: Region<'_>) -> Option<Symbol> {
fn early_bound_region_name(region: Region<'_>) -> Option<Symbol> {
match *region {
ty::ReEarlyParam(r) => Some(r.name),
_ => 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 FxIndexMap<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:?}"),
}
}
}

108
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::PredicateOrigin;
use rustc_hir_analysis::lower_ty;
use rustc_infer::infer::region_constraints::{Constraint, RegionConstraintData};
use rustc_middle::metadata::Reexport;
use rustc_middle::middle::resolve_bound_vars as rbv;
use rustc_middle::ty::fold::TypeFolder;
use rustc_middle::ty::GenericArgsRef;
use rustc_middle::ty::TypeVisitableExt;
use rustc_middle::ty::{self, AdtKind, Ty, TyCtxt};
@ -36,7 +34,6 @@ use rustc_trait_selection::traits::wf::object_region_bounds;
use std::borrow::Cow;
use std::collections::BTreeMap;
use std::hash::Hash;
use std::mem;
use thin_vec::ThinVec;
@ -501,6 +498,7 @@ fn projection_to_path_segment<'tcx>(
fn clean_generic_param_def<'tcx>(
def: &ty::GenericParamDef,
defaults: ParamDefaults,
cx: &mut DocContext<'tcx>,
) -> GenericParamDef {
let (name, kind) = match def.kind {
@ -508,7 +506,9 @@ fn clean_generic_param_def<'tcx>(
(def.name, GenericParamDefKind::Lifetime { outlives: ThinVec::new() })
}
ty::GenericParamDefKind::Type { has_default, synthetic, .. } => {
let default = if has_default {
let default = if let ParamDefaults::Yes = defaults
&& has_default
{
Some(clean_middle_ty(
ty::Binder::dummy(cx.tcx.type_of(def.def_id).instantiate_identity()),
cx,
@ -541,11 +541,14 @@ fn clean_generic_param_def<'tcx>(
Some(def.def_id),
None,
)),
default: match has_default {
true => Some(Box::new(
default: if let ParamDefaults::Yes = defaults
&& has_default
{
Some(Box::new(
cx.tcx.const_param_default(def.def_id).instantiate_identity().to_string(),
)),
false => None,
))
} else {
None
},
is_host_effect,
},
@ -555,6 +558,12 @@ fn clean_generic_param_def<'tcx>(
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>(
cx: &mut DocContext<'tcx>,
generics: Option<&hir::Generics<'tcx>>,
@ -758,34 +767,30 @@ fn clean_ty_generics<'tcx>(
gens: &ty::Generics,
preds: ty::GenericPredicates<'tcx>,
) -> Generics {
// Don't populate `cx.impl_trait_bounds` before `clean`ning `where` clauses,
// since `Clean for ty::Predicate` would consume them.
// Don't populate `cx.impl_trait_bounds` before cleaning where clauses,
// since `clean_predicate` would consume them.
let mut impl_trait = BTreeMap::<u32, Vec<GenericBound>>::default();
// Bounds in the type_params and lifetimes fields are repeated in the
// predicates field (see rustc_hir_analysis::collect::ty_generics), so remove
// them.
let stripped_params = gens
let params: ThinVec<_> = gens
.params
.iter()
.filter_map(|param| match param.kind {
ty::GenericParamDefKind::Lifetime if param.is_anonymous_lifetime() => None,
ty::GenericParamDefKind::Lifetime => Some(clean_generic_param_def(param, cx)),
.filter(|param| match param.kind {
ty::GenericParamDefKind::Lifetime => !param.is_anonymous_lifetime(),
ty::GenericParamDefKind::Type { synthetic, .. } => {
if param.name == kw::SelfUpper {
assert_eq!(param.index, 0);
return None;
debug_assert_eq!(param.index, 0);
return false;
}
if synthetic {
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 { .. } => Some(clean_generic_param_def(param, cx)),
ty::GenericParamDefKind::Const { is_host_effect, .. } => !is_host_effect,
})
.collect::<ThinVec<GenericParamDef>>();
.map(|param| clean_generic_param_def(param, ParamDefaults::Yes, cx))
.collect();
// param index -> [(trait DefId, associated type name & generics, term)]
let mut impl_trait_proj =
@ -881,56 +886,13 @@ fn clean_ty_generics<'tcx>(
// Now that `cx.impl_trait_bounds` is populated, we can process
// remaining predicates which could contain `impl Trait`.
let mut where_predicates =
where_predicates.into_iter().flat_map(|p| clean_predicate(*p, cx)).collect::<Vec<_>>();
let where_predicates =
where_predicates.into_iter().flat_map(|p| clean_predicate(*p, cx)).collect();
// 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'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),
}
let mut generics = Generics { params, where_predicates };
simplify::sized_bounds(cx, &mut generics);
generics.where_predicates = simplify::where_clauses(cx, generics.where_predicates);
generics
}
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!
use rustc_data_structures::fx::FxIndexMap;
use rustc_data_structures::unord::UnordSet;
use rustc_hir::def_id::DefId;
use rustc_middle::ty;
use thin_vec::ThinVec;
@ -21,7 +22,7 @@ use crate::clean::GenericArgs as PP;
use crate::clean::WherePredicate as WP;
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.
//
// 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_))
}
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
/// the respective parameter.
///

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

@ -1277,13 +1277,6 @@ impl GenericBound {
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> {
if let GenericBound::TraitBound(PolyTrait { ref trait_, .. }, _) = *self {
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::render_macro_matchers::render_macro_matcher;
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 {
let segments = match *p {
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(
cx: &mut DocContext<'_>,
item_def_id: DefId,
@ -493,8 +485,8 @@ pub(crate) fn get_auto_trait_and_blanket_impls(
let auto_impls = cx
.sess()
.prof
.generic_activity("get_auto_trait_impls")
.run(|| AutoTraitFinder::new(cx).get_auto_trait_impls(item_def_id));
.generic_activity("synthesize_auto_trait_impls")
.run(|| synthesize_auto_trait_impls(cx, item_def_id));
let blanket_impls = cx
.sess()
.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 - '//*[@id="synthetic-implementations-list"]//*[@class="impl"]//h3[@class="code-header"]' \
// "impl<'a, T, K: ?Sized> Send for Outer<'a, T, K>where 'a: 'static, T: MyTrait<'a>, \
// K: for<'b> Fn((&'b bool, &'a u8)) -> &'b i8, <T as MyTrait<'a>>::MyItem: Copy,"
// "impl<'a, T, K> Send for Outer<'a, T, K>where 'a: 'static, T: MyTrait<'a>, \
// 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};