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Remove hir::GenericBound::Unsized #88061

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Sep 8, 2021
Merged

Remove hir::GenericBound::Unsized #88061

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2eaf9fe
Static assert size of GenericBoun to ensure size doesn't change
jackh726 Aug 15, 2021
f1f1d56
Don't move ?Trait bounds to param bounds if they're in where clauses
jackh726 Aug 15, 2021
216906f
Change is_unsized to add_implicitly_sized
jackh726 Aug 15, 2021
22ef04e
A bit of cleanup to astconv
jackh726 Aug 15, 2021
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46 changes: 16 additions & 30 deletions compiler/rustc_ast_lowering/src/item.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,6 @@ use super::{AnonymousLifetimeMode, LoweringContext, ParamMode};
use super::{ImplTraitContext, ImplTraitPosition};
use crate::Arena;

use rustc_ast::node_id::NodeMap;
use rustc_ast::ptr::P;
use rustc_ast::visit::{self, AssocCtxt, FnCtxt, FnKind, Visitor};
use rustc_ast::*;
Expand Down Expand Up @@ -1351,8 +1350,11 @@ impl<'hir> LoweringContext<'_, 'hir> {
generics: &Generics,
itctx: ImplTraitContext<'_, 'hir>,
) -> GenericsCtor<'hir> {
// Collect `?Trait` bounds in where clause and move them to parameter definitions.
let mut add_bounds: NodeMap<Vec<_>> = Default::default();
// Error if `?Trait` bounds in where clauses don't refer directly to type paramters.
// Note: we used to clone these bounds directly onto the type parameter (and avoid lowering
// these into hir when we lower thee where clauses), but this makes it quite difficult to
// keep track of the Span info. Now, `add_implicitly_sized` in `AstConv` checks both param bounds and
// where clauses for `?Sized`.
for pred in &generics.where_clause.predicates {
if let WherePredicate::BoundPredicate(ref bound_pred) = *pred {
'next_bound: for bound in &bound_pred.bounds {
Expand All @@ -1368,7 +1370,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
{
for param in &generics.params {
if def_id == self.resolver.local_def_id(param.id).to_def_id() {
add_bounds.entry(param.id).or_default().push(bound.clone());
continue 'next_bound;
}
}
Expand All @@ -1386,7 +1387,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
}

GenericsCtor {
params: self.lower_generic_params_mut(&generics.params, &add_bounds, itctx).collect(),
params: self.lower_generic_params_mut(&generics.params, itctx).collect(),
where_clause: self.lower_where_clause(&generics.where_clause),
span: self.lower_span(generics.span),
}
Expand Down Expand Up @@ -1419,32 +1420,17 @@ impl<'hir> LoweringContext<'_, 'hir> {
ref bounded_ty,
ref bounds,
span,
}) => {
self.with_in_scope_lifetime_defs(&bound_generic_params, |this| {
hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
bound_generic_params: this.lower_generic_params(
bound_generic_params,
&NodeMap::default(),
ImplTraitContext::disallowed(),
),
bounded_ty: this.lower_ty(bounded_ty, ImplTraitContext::disallowed()),
bounds: this.arena.alloc_from_iter(bounds.iter().map(
|bound| match bound {
// We used to ignore `?Trait` bounds, as they were copied into type
// parameters already, but we need to keep them around only for
// diagnostics when we suggest removal of `?Sized` bounds. See
// `suggest_constraining_type_param`. This will need to change if
// we ever allow something *other* than `?Sized`.
GenericBound::Trait(p, TraitBoundModifier::Maybe) => {
hir::GenericBound::Unsized(this.lower_span(p.span))
}
_ => this.lower_param_bound(bound, ImplTraitContext::disallowed()),
},
)),
span: this.lower_span(span),
})
}) => self.with_in_scope_lifetime_defs(&bound_generic_params, |this| {
hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
bound_generic_params: this
.lower_generic_params(bound_generic_params, ImplTraitContext::disallowed()),
bounded_ty: this.lower_ty(bounded_ty, ImplTraitContext::disallowed()),
bounds: this.arena.alloc_from_iter(bounds.iter().map(|bound| {
this.lower_param_bound(bound, ImplTraitContext::disallowed())
})),
span: this.lower_span(span),
})
}
}),
WherePredicate::RegionPredicate(WhereRegionPredicate {
ref lifetime,
ref bounds,
Expand Down
25 changes: 5 additions & 20 deletions compiler/rustc_ast_lowering/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1313,7 +1313,6 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
hir::TyKind::BareFn(this.arena.alloc(hir::BareFnTy {
generic_params: this.lower_generic_params(
&f.generic_params,
&NodeMap::default(),
ImplTraitContext::disallowed(),
),
unsafety: this.lower_unsafety(f.unsafety),
Expand Down Expand Up @@ -1998,30 +1997,25 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
fn lower_generic_params_mut<'s>(
&'s mut self,
params: &'s [GenericParam],
add_bounds: &'s NodeMap<Vec<GenericBound>>,
mut itctx: ImplTraitContext<'s, 'hir>,
) -> impl Iterator<Item = hir::GenericParam<'hir>> + Captures<'a> + Captures<'s> {
params
.iter()
.map(move |param| self.lower_generic_param(param, add_bounds, itctx.reborrow()))
params.iter().map(move |param| self.lower_generic_param(param, itctx.reborrow()))
}

fn lower_generic_params(
&mut self,
params: &[GenericParam],
add_bounds: &NodeMap<Vec<GenericBound>>,
itctx: ImplTraitContext<'_, 'hir>,
) -> &'hir [hir::GenericParam<'hir>] {
self.arena.alloc_from_iter(self.lower_generic_params_mut(params, add_bounds, itctx))
self.arena.alloc_from_iter(self.lower_generic_params_mut(params, itctx))
}

fn lower_generic_param(
&mut self,
param: &GenericParam,
add_bounds: &NodeMap<Vec<GenericBound>>,
mut itctx: ImplTraitContext<'_, 'hir>,
) -> hir::GenericParam<'hir> {
let mut bounds: Vec<_> = self
let bounds: Vec<_> = self
.with_anonymous_lifetime_mode(AnonymousLifetimeMode::ReportError, |this| {
this.lower_param_bounds_mut(&param.bounds, itctx.reborrow()).collect()
});
Expand Down Expand Up @@ -2057,12 +2051,6 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
(param_name, kind)
}
GenericParamKind::Type { ref default, .. } => {
let add_bounds = add_bounds.get(&param.id).map_or(&[][..], |x| &x);
if !add_bounds.is_empty() {
let params = self.lower_param_bounds_mut(add_bounds, itctx.reborrow());
bounds.extend(params);
}

let kind = hir::GenericParamKind::Type {
default: default.as_ref().map(|x| {
self.lower_ty(x, ImplTraitContext::Disallowed(ImplTraitPosition::Other))
Expand Down Expand Up @@ -2123,11 +2111,8 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
p: &PolyTraitRef,
mut itctx: ImplTraitContext<'_, 'hir>,
) -> hir::PolyTraitRef<'hir> {
let bound_generic_params = self.lower_generic_params(
&p.bound_generic_params,
&NodeMap::default(),
itctx.reborrow(),
);
let bound_generic_params =
self.lower_generic_params(&p.bound_generic_params, itctx.reborrow());

let trait_ref = self.with_in_scope_lifetime_defs(&p.bound_generic_params, |this| {
// Any impl Trait types defined within this scope can capture
Expand Down
5 changes: 3 additions & 2 deletions compiler/rustc_hir/src/hir.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -441,10 +441,12 @@ pub enum GenericBound<'hir> {
Trait(PolyTraitRef<'hir>, TraitBoundModifier),
// FIXME(davidtwco): Introduce `PolyTraitRef::LangItem`
LangItemTrait(LangItem, Span, HirId, &'hir GenericArgs<'hir>),
Unsized(Span),
Outlives(Lifetime),
}

#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
rustc_data_structures::static_assert_size!(GenericBound<'_>, 48);

impl GenericBound<'_> {
pub fn trait_ref(&self) -> Option<&TraitRef<'_>> {
match self {
Expand All @@ -458,7 +460,6 @@ impl GenericBound<'_> {
GenericBound::Trait(t, ..) => t.span,
GenericBound::LangItemTrait(_, span, ..) => *span,
GenericBound::Outlives(l) => l.span,
GenericBound::Unsized(span) => *span,
}
}
}
Expand Down
1 change: 0 additions & 1 deletion compiler/rustc_hir/src/intravisit.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -871,7 +871,6 @@ pub fn walk_param_bound<'v, V: Visitor<'v>>(visitor: &mut V, bound: &'v GenericB
visitor.visit_generic_args(span, args);
}
GenericBound::Outlives(ref lifetime) => visitor.visit_lifetime(lifetime),
GenericBound::Unsized(_) => {}
}
}

Expand Down
3 changes: 0 additions & 3 deletions compiler/rustc_hir_pretty/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2232,9 +2232,6 @@ impl<'a> State<'a> {
GenericBound::Outlives(lt) => {
self.print_lifetime(lt);
}
GenericBound::Unsized(_) => {
self.s.word("?Sized");
}
}
}
}
Expand Down
12 changes: 3 additions & 9 deletions compiler/rustc_middle/src/ty/diagnostics.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,6 @@

use crate::ty::TyKind::*;
use crate::ty::{InferTy, TyCtxt, TyS};
use rustc_data_structures::fx::FxHashSet;
use rustc_errors::{Applicability, DiagnosticBuilder};
use rustc_hir as hir;
use rustc_hir::def_id::DefId;
Expand Down Expand Up @@ -114,10 +113,8 @@ fn suggest_removing_unsized_bound(
def_id: Option<DefId>,
) {
// See if there's a `?Sized` bound that can be removed to suggest that.
// First look at the `where` clause because we can have `where T: ?Sized`, but that
// `?Sized` bound is *also* included in the `GenericParam` as a bound, which breaks
// the spans. Hence the somewhat involved logic that follows.
let mut where_unsized_bounds = FxHashSet::default();
// First look at the `where` clause because we can have `where T: ?Sized`,
// then look at params.
for (where_pos, predicate) in generics.where_clause.predicates.iter().enumerate() {
match predicate {
WherePredicate::BoundPredicate(WhereBoundPredicate {
Expand All @@ -140,7 +137,6 @@ fn suggest_removing_unsized_bound(
}) if segment.ident.as_str() == param_name => {
for (pos, bound) in bounds.iter().enumerate() {
match bound {
hir::GenericBound::Unsized(_) => {}
hir::GenericBound::Trait(poly, hir::TraitBoundModifier::Maybe)
if poly.trait_ref.trait_def_id() == def_id => {}
_ => continue,
Expand Down Expand Up @@ -173,7 +169,6 @@ fn suggest_removing_unsized_bound(
// ^^^^^^^^^
(_, pos, _, _) => bounds[pos - 1].span().shrink_to_hi().to(bound.span()),
};
where_unsized_bounds.insert(bound.span());
err.span_suggestion_verbose(
sp,
"consider removing the `?Sized` bound to make the \
Expand All @@ -189,8 +184,7 @@ fn suggest_removing_unsized_bound(
for (pos, bound) in param.bounds.iter().enumerate() {
match bound {
hir::GenericBound::Trait(poly, hir::TraitBoundModifier::Maybe)
if poly.trait_ref.trait_def_id() == def_id
&& !where_unsized_bounds.contains(&bound.span()) =>
if poly.trait_ref.trait_def_id() == def_id =>
{
let sp = match (param.bounds.len(), pos) {
// T: ?Sized,
Expand Down
1 change: 0 additions & 1 deletion compiler/rustc_save_analysis/src/dump_visitor.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -693,7 +693,6 @@ impl<'tcx> DumpVisitor<'tcx> {
(Some(self.tcx.require_lang_item(lang_item, Some(span))), span)
}
hir::GenericBound::Outlives(..) => continue,
hir::GenericBound::Unsized(_) => continue,
};

if let Some(id) = def_id {
Expand Down
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