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Don't move ?Trait bounds to param bounds if they're in where clauses

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This commit is contained in:
jackh726 2021-08-15 00:53:40 -04:00
parent 2eaf9fe364
commit f1f1d56d93
12 changed files with 103 additions and 82 deletions
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40
compiler/rustc_ast_lowering/src/item.rs
View File

@ -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::*;
@ -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, `is_unsized` 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 {
@ -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;
}
}
@ -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),
}
@ -1419,32 +1420,17 @@ impl<'hir> LoweringContext<'_, 'hir> {
ref bounded_ty,
ref bounds,
span,
}) => {
self.with_in_scope_lifetime_defs(&bound_generic_params, |this| {
}) => 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(),
),
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| 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()),
},
)),
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,

25
compiler/rustc_ast_lowering/src/lib.rs
View File

@ -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),
@ -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()
});
@ -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))
@ -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

2
compiler/rustc_hir/src/hir.rs
View File

@ -441,7 +441,6 @@ pub enum GenericBound<'hir> {
Trait(PolyTraitRef<'hir>, TraitBoundModifier),
// FIXME(davidtwco): Introduce `PolyTraitRef::LangItem`
LangItemTrait(LangItem, Span, HirId, &'hir GenericArgs<'hir>),
Unsized(Span),
Outlives(Lifetime),
}
@ -461,7 +460,6 @@ impl GenericBound<'_> {
GenericBound::Trait(t, ..) => t.span,
GenericBound::LangItemTrait(_, span, ..) => *span,
GenericBound::Outlives(l) => l.span,
GenericBound::Unsized(span) => *span,
}
}
}

1
compiler/rustc_hir/src/intravisit.rs
View File

@ -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(_) => {}
}
}

3
compiler/rustc_hir_pretty/src/lib.rs
View File

@ -2232,9 +2232,6 @@ impl<'a> State<'a> {
GenericBound::Outlives(lt) => {
self.print_lifetime(lt);
}
GenericBound::Unsized(_) => {
self.s.word("?Sized");
}
}
}
}

12
compiler/rustc_middle/src/ty/diagnostics.rs
View File

@ -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;
@ -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 {
@ -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,
@ -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 \
@ -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,

1
compiler/rustc_save_analysis/src/dump_visitor.rs
View File

@ -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 {

67
compiler/rustc_typeck/src/astconv/mod.rs
View File

@ -854,7 +854,13 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
}
// Returns `true` if a bounds list includes `?Sized`.
pub fn is_unsized(&self, ast_bounds: &[hir::GenericBound<'_>], span: Span) -> bool {
fn is_unsized(
&self,
ast_bounds: &[hir::GenericBound<'_>],
self_ty: Option<hir::HirId>,
where_clause: Option<&[hir::WherePredicate<'_>]>,
span: Span,
) -> bool {
let tcx = self.tcx();
// Try to find an unbound in bounds.
@ -868,11 +874,38 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
}
}
}
if let (Some(self_ty), Some(where_clause)) = (self_ty, where_clause) {
let self_ty_def_id = tcx.hir().local_def_id(self_ty).to_def_id();
for clause in where_clause {
match clause {
hir::WherePredicate::BoundPredicate(pred) => {
match pred.bounded_ty.kind {
hir::TyKind::Path(hir::QPath::Resolved(_, path)) => match path.res {
Res::Def(DefKind::TyParam, def_id) if def_id == self_ty_def_id => {}
_ => continue,
},
_ => continue,
}
for ab in pred.bounds {
if let hir::GenericBound::Trait(ptr, hir::TraitBoundModifier::Maybe) =
ab
{
if unbound.is_none() {
unbound = Some(&ptr.trait_ref);
} else {
tcx.sess.emit_err(MultipleRelaxedDefaultBounds { span });
}
}
}
}
_ => {}
}
}
}
let kind_id = tcx.lang_items().require(LangItem::Sized);
match unbound {
Some(tpb) => {
// FIXME(#8559) currently requires the unbound to be built-in.
if let Ok(kind_id) = kind_id {
if tpb.path.res != Res::Def(DefKind::Trait, kind_id) {
tcx.sess.span_warn(
@ -940,8 +973,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
false,
);
}
hir::GenericBound::Trait(_, hir::TraitBoundModifier::Maybe)
| hir::GenericBound::Unsized(_) => {}
hir::GenericBound::Trait(_, hir::TraitBoundModifier::Maybe) => {}
hir::GenericBound::LangItemTrait(lang_item, span, hir_id, args) => self
.instantiate_lang_item_trait_ref(
lang_item, span, hir_id, args, param_ty, bounds,
@ -970,22 +1002,33 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
/// example above, but is not true in supertrait listings like `trait Foo: Bar + Baz`.
///
/// `span` should be the declaration size of the parameter.
pub fn compute_bounds(
pub(crate) fn compute_bounds(
&self,
param_ty: Ty<'tcx>,
ast_bounds: &[hir::GenericBound<'_>],
self_ty: Option<hir::HirId>,
where_clause: Option<&[hir::WherePredicate<'_>]>,
sized_by_default: SizedByDefault,
span: Span,
) -> Bounds<'tcx> {
self.compute_bounds_inner(param_ty, &ast_bounds, sized_by_default, span)
self.compute_bounds_inner(
param_ty,
&ast_bounds,
self_ty,
where_clause,
sized_by_default,
span,
)
}
/// Convert the bounds in `ast_bounds` that refer to traits which define an associated type
/// named `assoc_name` into ty::Bounds. Ignore the rest.
pub fn compute_bounds_that_match_assoc_type(
pub(crate) fn compute_bounds_that_match_assoc_type(
&self,
param_ty: Ty<'tcx>,
ast_bounds: &[hir::GenericBound<'_>],
self_ty: Option<hir::HirId>,
where_clause: Option<&[hir::WherePredicate<'_>]>,
sized_by_default: SizedByDefault,
span: Span,
assoc_name: Ident,
@ -1002,13 +1045,15 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
}
}
self.compute_bounds_inner(param_ty, &result, sized_by_default, span)
self.compute_bounds_inner(param_ty, &result, self_ty, where_clause, sized_by_default, span)
}
fn compute_bounds_inner(
&self,
param_ty: Ty<'tcx>,
ast_bounds: &[hir::GenericBound<'_>],
self_ty: Option<hir::HirId>,
where_clause: Option<&[hir::WherePredicate<'_>]>,
sized_by_default: SizedByDefault,
span: Span,
) -> Bounds<'tcx> {
@ -1017,7 +1062,11 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
self.add_bounds(param_ty, ast_bounds, &mut bounds, ty::List::empty());
bounds.implicitly_sized = if let SizedByDefault::Yes = sized_by_default {
if !self.is_unsized(ast_bounds, span) { Some(span) } else { None }
if !self.is_unsized(ast_bounds, self_ty, where_clause, span) {
Some(span)
} else {
None
}
} else {
None
};

9
compiler/rustc_typeck/src/collect.rs
View File

@ -1156,6 +1156,8 @@ fn super_predicates_that_define_assoc_type(
&icx,
self_param_ty,
&bounds,
None,
None,
SizedByDefault::No,
item.span,
assoc_name,
@ -1165,6 +1167,8 @@ fn super_predicates_that_define_assoc_type(
&icx,
self_param_ty,
&bounds,
None,
None,
SizedByDefault::No,
item.span,
)
@ -2181,6 +2185,8 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericP
&icx,
param_ty,
&param.bounds,
Some(param.hir_id),
Some(ast_generics.where_clause.predicates),
sized,
param.span,
);
@ -2267,8 +2273,6 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::GenericP
predicates.extend(bounds.predicates(tcx, ty));
}
hir::GenericBound::Unsized(_) => {}
hir::GenericBound::Outlives(lifetime) => {
let region =
<dyn AstConv<'_>>::ast_region_to_region(&icx, lifetime, None);
@ -2529,7 +2533,6 @@ fn predicates_from_bound<'tcx>(
);
bounds.predicates(astconv.tcx(), param_ty)
}
hir::GenericBound::Unsized(_) => vec![],
hir::GenericBound::Outlives(ref lifetime) => {
let region = astconv.ast_region_to_region(lifetime, None);
let pred = ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(param_ty, region))

4
compiler/rustc_typeck/src/collect/item_bounds.rs
View File

@ -29,6 +29,8 @@ fn associated_type_bounds<'tcx>(
&ItemCtxt::new(tcx, assoc_item_def_id),
item_ty,
&bounds,
None,
None,
SizedByDefault::Yes,
span,
);
@ -70,6 +72,8 @@ fn opaque_type_bounds<'tcx>(
&ItemCtxt::new(tcx, opaque_def_id),
item_ty,
&bounds,
None,
None,
SizedByDefault::Yes,
span,
)

1
src/test/ui/maybe-bounds-where.rs
View File

@ -11,6 +11,7 @@ trait Trait<'a> {}
struct S4<T>(T) where for<'a> T: ?Trait<'a>;
//~^ ERROR `?Trait` bounds are only permitted at the point where a type parameter is declared
//~| WARN default bound relaxed for a type parameter
struct S5<T>(*const T) where T: ?Trait<'static> + ?Sized;
//~^ ERROR type parameter has more than one relaxed default bound

14
src/test/ui/maybe-bounds-where.stderr
View File

@ -23,23 +23,29 @@ LL | struct S4<T>(T) where for<'a> T: ?Trait<'a>;
| ^
error: `?Trait` bounds are only permitted at the point where a type parameter is declared
--> $DIR/maybe-bounds-where.rs:20:18
--> $DIR/maybe-bounds-where.rs:21:18
|
LL | fn f() where T: ?Sized {}
| ^
warning: default bound relaxed for a type parameter, but this does nothing because the given bound is not a default; only `?Sized` is supported
--> $DIR/maybe-bounds-where.rs:12:11
|
LL | struct S4<T>(T) where for<'a> T: ?Trait<'a>;
| ^
error[E0203]: type parameter has more than one relaxed default bound, only one is supported
--> $DIR/maybe-bounds-where.rs:15:11
--> $DIR/maybe-bounds-where.rs:16:11
|
LL | struct S5<T>(*const T) where T: ?Trait<'static> + ?Sized;
| ^
warning: default bound relaxed for a type parameter, but this does nothing because the given bound is not a default; only `?Sized` is supported
--> $DIR/maybe-bounds-where.rs:15:11
--> $DIR/maybe-bounds-where.rs:16:11
|
LL | struct S5<T>(*const T) where T: ?Trait<'static> + ?Sized;
| ^
error: aborting due to 6 previous errors; 1 warning emitted
error: aborting due to 6 previous errors; 2 warnings emitted
For more information about this error, try `rustc --explain E0203`.