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Check Sizedness of return type in WF
1 parent bf1b174 commit b9f4561

32 files changed

+360
-369
lines changed

‎compiler/rustc_hir_analysis/src/check/wfcheck.rs

+26
Original file line numberDiff line numberDiff line change
@@ -1059,6 +1059,7 @@ fn check_associated_item(
10591059
let ty = tcx.type_of(item.def_id).instantiate_identity();
10601060
let ty = wfcx.normalize(span, Some(WellFormedLoc::Ty(item_id)), ty);
10611061
wfcx.register_wf_obligation(span, loc, ty.into());
1062+
check_sized_if_body(wfcx, item.def_id.expect_local(), ty, Some(span));
10621063
Ok(())
10631064
}
10641065
ty::AssocKind::Fn => {
@@ -1640,6 +1641,31 @@ fn check_fn_or_method<'tcx>(
16401641
);
16411642
}
16421643
}
1644+
1645+
// If the function has a body, additionally require that the return type is sized.
1646+
check_sized_if_body(wfcx, def_id, sig.output(), match hir_decl.output {
1647+
hir::FnRetTy::Return(ty) => Some(ty.span),
1648+
hir::FnRetTy::DefaultReturn(_) => None,
1649+
});
1650+
}
1651+
1652+
fn check_sized_if_body<'tcx>(
1653+
wfcx: &WfCheckingCtxt<'_, 'tcx>,
1654+
def_id: LocalDefId,
1655+
ty: Ty<'tcx>,
1656+
maybe_span: Option<Span>,
1657+
) {
1658+
let tcx = wfcx.tcx();
1659+
if let Some(body) = tcx.hir().maybe_body_owned_by(def_id) {
1660+
let span = maybe_span.unwrap_or(body.value.span);
1661+
1662+
wfcx.register_bound(
1663+
ObligationCause::new(span, def_id, traits::ObligationCauseCode::SizedReturnType),
1664+
wfcx.param_env,
1665+
ty,
1666+
tcx.require_lang_item(LangItem::Sized, None),
1667+
);
1668+
}
16431669
}
16441670

16451671
/// The `arbitrary_self_types_pointers` feature implies `arbitrary_self_types`.

‎compiler/rustc_hir_typeck/src/check.rs

+1-6
Original file line numberDiff line numberDiff line change
@@ -122,12 +122,7 @@ pub(super) fn check_fn<'a, 'tcx>(
122122
hir::FnRetTy::Return(ty) => ty.span,
123123
};
124124

125-
fcx.require_type_is_sized(
126-
declared_ret_ty,
127-
return_or_body_span,
128-
ObligationCauseCode::SizedReturnType,
129-
);
130-
// We checked the root's signature during wfcheck, but not the child.
125+
// We checked the root's ret ty during wfcheck, but not the child.
131126
if fcx.tcx.is_typeck_child(fn_def_id.to_def_id()) {
132127
fcx.require_type_is_sized(
133128
declared_ret_ty,

‎compiler/rustc_hir_typeck/src/lib.rs

-2
Original file line numberDiff line numberDiff line change
@@ -186,8 +186,6 @@ fn typeck_with_inspect<'tcx>(
186186
let wf_code = ObligationCauseCode::WellFormed(Some(WellFormedLoc::Ty(def_id)));
187187
fcx.register_wf_obligation(expected_type.into(), body.value.span, wf_code);
188188

189-
fcx.require_type_is_sized(expected_type, body.value.span, ObligationCauseCode::ConstSized);
190-
191189
// Gather locals in statics (because of block expressions).
192190
GatherLocalsVisitor::new(&fcx).visit_body(body);
193191

‎compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs

-5
Original file line numberDiff line numberDiff line change
@@ -714,7 +714,6 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
714714
};
715715

716716
self.note_obligation_cause(&mut err, &obligation);
717-
self.point_at_returns_when_relevant(&mut err, &obligation);
718717
err.emit()
719718
}
720719
}
@@ -814,7 +813,6 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
814813
"Async",
815814
);
816815
self.note_obligation_cause(&mut err, &obligation);
817-
self.point_at_returns_when_relevant(&mut err, &obligation);
818816
return Some(err.emit());
819817
}
820818
}
@@ -860,7 +858,6 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
860858
"",
861859
);
862860
self.note_obligation_cause(&mut err, &obligation);
863-
self.point_at_returns_when_relevant(&mut err, &obligation);
864861
return Some(err.emit());
865862
}
866863

@@ -876,7 +873,6 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
876873
kind: expected_kind.as_str(),
877874
});
878875
self.note_obligation_cause(&mut err, &obligation);
879-
self.point_at_returns_when_relevant(&mut err, &obligation);
880876
return Some(err.emit());
881877
}
882878
}
@@ -2784,7 +2780,6 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
27842780
err.span_note(self.tcx.def_span(def_id), "opaque type is declared here");
27852781

27862782
self.note_obligation_cause(&mut err, &obligation);
2787-
self.point_at_returns_when_relevant(&mut err, &obligation);
27882783
self.dcx().try_steal_replace_and_emit_err(self.tcx.def_span(def_id), StashKey::Cycle, err)
27892784
}
27902785

‎compiler/rustc_trait_selection/src/error_reporting/traits/overflow.rs

-1
Original file line numberDiff line numberDiff line change
@@ -196,7 +196,6 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
196196
suggest_increasing_limit,
197197
);
198198
self.note_obligation_cause(&mut err, &obligation);
199-
self.point_at_returns_when_relevant(&mut err, &obligation);
200199
err.emit()
201200
}
202201
}

‎compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs

+8-55
Original file line numberDiff line numberDiff line change
@@ -1789,25 +1789,13 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
17891789
} else {
17901790
("dyn ", span.shrink_to_lo())
17911791
};
1792-
let alternatively = if visitor
1793-
.returns
1794-
.iter()
1795-
.map(|expr| self.typeck_results.as_ref().unwrap().expr_ty_adjusted_opt(expr))
1796-
.collect::<FxHashSet<_>>()
1797-
.len()
1798-
<= 1
1799-
{
1800-
err.span_suggestion_verbose(
1801-
impl_span,
1802-
"consider returning an `impl Trait` instead of a `dyn Trait`",
1803-
"impl ",
1804-
Applicability::MaybeIncorrect,
1805-
);
1806-
"alternatively, "
1807-
} else {
1808-
err.help("if there were a single returned type, you could use `impl Trait` instead");
1809-
""
1810-
};
1792+
1793+
err.span_suggestion_verbose(
1794+
impl_span,
1795+
"consider returning an `impl Trait` instead of a `dyn Trait`",
1796+
"impl ",
1797+
Applicability::MaybeIncorrect,
1798+
);
18111799

18121800
let mut sugg = vec![
18131801
(span.shrink_to_lo(), format!("Box<{pre}")),
@@ -1839,7 +1827,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
18391827

18401828
err.multipart_suggestion(
18411829
format!(
1842-
"{alternatively}box the return type, and wrap all of the returned values in \
1830+
"alternatively, box the return type, and wrap all of the returned values in \
18431831
`Box::new`",
18441832
),
18451833
sugg,
@@ -1849,41 +1837,6 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
18491837
true
18501838
}
18511839

1852-
pub(super) fn point_at_returns_when_relevant(
1853-
&self,
1854-
err: &mut Diag<'_>,
1855-
obligation: &PredicateObligation<'tcx>,
1856-
) {
1857-
match obligation.cause.code().peel_derives() {
1858-
ObligationCauseCode::SizedReturnType => {}
1859-
_ => return,
1860-
}
1861-
1862-
let hir = self.tcx.hir();
1863-
let node = self.tcx.hir_node_by_def_id(obligation.cause.body_id);
1864-
if let hir::Node::Item(hir::Item {
1865-
kind: hir::ItemKind::Fn { body: body_id, .. }, ..
1866-
}) = node
1867-
{
1868-
let body = hir.body(*body_id);
1869-
// Point at all the `return`s in the function as they have failed trait bounds.
1870-
let mut visitor = ReturnsVisitor::default();
1871-
visitor.visit_body(body);
1872-
let typeck_results = self.typeck_results.as_ref().unwrap();
1873-
for expr in &visitor.returns {
1874-
if let Some(returned_ty) = typeck_results.node_type_opt(expr.hir_id) {
1875-
let ty = self.resolve_vars_if_possible(returned_ty);
1876-
if ty.references_error() {
1877-
// don't print out the [type error] here
1878-
err.downgrade_to_delayed_bug();
1879-
} else {
1880-
err.span_label(expr.span, format!("this returned value is of type `{ty}`"));
1881-
}
1882-
}
1883-
}
1884-
}
1885-
}
1886-
18871840
pub(super) fn report_closure_arg_mismatch(
18881841
&self,
18891842
span: Span,

‎tests/ui/associated-consts/issue-58022.stderr

+9-9
Original file line numberDiff line numberDiff line change
@@ -1,12 +1,3 @@
1-
error[E0790]: cannot refer to the associated constant on trait without specifying the corresponding `impl` type
2-
--> $DIR/issue-58022.rs:4:25
3-
|
4-
LL | const SIZE: usize;
5-
| ------------------ `Foo::SIZE` defined here
6-
LL |
7-
LL | fn new(slice: &[u8; Foo::SIZE]) -> Self;
8-
| ^^^^^^^^^ cannot refer to the associated constant of trait
9-
101
error[E0277]: the size for values of type `[u8]` cannot be known at compilation time
112
--> $DIR/issue-58022.rs:13:41
123
|
@@ -21,6 +12,15 @@ LL | pub struct Bar<T: ?Sized>(T);
2112
| ^^^
2213
= note: the return type of a function must have a statically known size
2314

15+
error[E0790]: cannot refer to the associated constant on trait without specifying the corresponding `impl` type
16+
--> $DIR/issue-58022.rs:4:25
17+
|
18+
LL | const SIZE: usize;
19+
| ------------------ `Foo::SIZE` defined here
20+
LL |
21+
LL | fn new(slice: &[u8; Foo::SIZE]) -> Self;
22+
| ^^^^^^^^^ cannot refer to the associated constant of trait
23+
2424
error[E0423]: expected function, tuple struct or tuple variant, found trait `Foo`
2525
--> $DIR/issue-58022.rs:15:9
2626
|

‎tests/ui/consts/const-unsized.rs

+4-4
Original file line numberDiff line numberDiff line change
@@ -2,19 +2,19 @@ use std::fmt::Debug;
22

33
const CONST_0: dyn Debug + Sync = *(&0 as &(dyn Debug + Sync));
44
//~^ ERROR the size for values of type
5-
//~| ERROR the size for values of type
5+
//~| ERROR cannot move out of a shared reference
66

77
const CONST_FOO: str = *"foo";
88
//~^ ERROR the size for values of type
9-
//~| ERROR the size for values of type
9+
//~| ERROR cannot move out of a shared reference
1010

1111
static STATIC_1: dyn Debug + Sync = *(&1 as &(dyn Debug + Sync));
1212
//~^ ERROR the size for values of type
13-
//~| ERROR the size for values of type
13+
//~| ERROR cannot move out of a shared reference
1414

1515
static STATIC_BAR: str = *"bar";
1616
//~^ ERROR the size for values of type
17-
//~| ERROR the size for values of type
17+
//~| ERROR cannot move out of a shared reference
1818

1919
fn main() {
2020
println!("{:?} {:?} {:?} {:?}", &CONST_0, &CONST_FOO, &STATIC_1, &STATIC_BAR);

‎tests/ui/consts/const-unsized.stderr

+21-33
Original file line numberDiff line numberDiff line change
@@ -6,15 +6,6 @@ LL | const CONST_0: dyn Debug + Sync = *(&0 as &(dyn Debug + Sync));
66
|
77
= help: the trait `Sized` is not implemented for `(dyn Debug + Sync + 'static)`
88

9-
error[E0277]: the size for values of type `(dyn Debug + Sync + 'static)` cannot be known at compilation time
10-
--> $DIR/const-unsized.rs:3:35
11-
|
12-
LL | const CONST_0: dyn Debug + Sync = *(&0 as &(dyn Debug + Sync));
13-
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
14-
|
15-
= help: the trait `Sized` is not implemented for `(dyn Debug + Sync + 'static)`
16-
= note: constant expressions must have a statically known size
17-
189
error[E0277]: the size for values of type `str` cannot be known at compilation time
1910
--> $DIR/const-unsized.rs:7:18
2011
|
@@ -23,15 +14,6 @@ LL | const CONST_FOO: str = *"foo";
2314
|
2415
= help: the trait `Sized` is not implemented for `str`
2516

26-
error[E0277]: the size for values of type `str` cannot be known at compilation time
27-
--> $DIR/const-unsized.rs:7:24
28-
|
29-
LL | const CONST_FOO: str = *"foo";
30-
| ^^^^^^ doesn't have a size known at compile-time
31-
|
32-
= help: the trait `Sized` is not implemented for `str`
33-
= note: constant expressions must have a statically known size
34-
3517
error[E0277]: the size for values of type `(dyn Debug + Sync + 'static)` cannot be known at compilation time
3618
--> $DIR/const-unsized.rs:11:18
3719
|
@@ -40,15 +22,6 @@ LL | static STATIC_1: dyn Debug + Sync = *(&1 as &(dyn Debug + Sync));
4022
|
4123
= help: the trait `Sized` is not implemented for `(dyn Debug + Sync + 'static)`
4224

43-
error[E0277]: the size for values of type `(dyn Debug + Sync + 'static)` cannot be known at compilation time
44-
--> $DIR/const-unsized.rs:11:37
45-
|
46-
LL | static STATIC_1: dyn Debug + Sync = *(&1 as &(dyn Debug + Sync));
47-
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
48-
|
49-
= help: the trait `Sized` is not implemented for `(dyn Debug + Sync + 'static)`
50-
= note: constant expressions must have a statically known size
51-
5225
error[E0277]: the size for values of type `str` cannot be known at compilation time
5326
--> $DIR/const-unsized.rs:15:20
5427
|
@@ -57,14 +30,29 @@ LL | static STATIC_BAR: str = *"bar";
5730
|
5831
= help: the trait `Sized` is not implemented for `str`
5932

60-
error[E0277]: the size for values of type `str` cannot be known at compilation time
33+
error[E0507]: cannot move out of a shared reference
34+
--> $DIR/const-unsized.rs:3:35
35+
|
36+
LL | const CONST_0: dyn Debug + Sync = *(&0 as &(dyn Debug + Sync));
37+
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ move occurs because value has type `dyn Debug + Sync`, which does not implement the `Copy` trait
38+
39+
error[E0507]: cannot move out of a shared reference
40+
--> $DIR/const-unsized.rs:7:24
41+
|
42+
LL | const CONST_FOO: str = *"foo";
43+
| ^^^^^^ move occurs because value has type `str`, which does not implement the `Copy` trait
44+
45+
error[E0507]: cannot move out of a shared reference
46+
--> $DIR/const-unsized.rs:11:37
47+
|
48+
LL | static STATIC_1: dyn Debug + Sync = *(&1 as &(dyn Debug + Sync));
49+
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ move occurs because value has type `dyn Debug + Sync`, which does not implement the `Copy` trait
50+
51+
error[E0507]: cannot move out of a shared reference
6152
--> $DIR/const-unsized.rs:15:26
6253
|
6354
LL | static STATIC_BAR: str = *"bar";
64-
| ^^^^^^ doesn't have a size known at compile-time
65-
|
66-
= help: the trait `Sized` is not implemented for `str`
67-
= note: constant expressions must have a statically known size
55+
| ^^^^^^ move occurs because value has type `str`, which does not implement the `Copy` trait
6856

6957
error[E0161]: cannot move a value of type `str`
7058
--> $DIR/const-unsized.rs:20:48
@@ -80,5 +68,5 @@ LL | println!("{:?} {:?} {:?} {:?}", &CONST_0, &CONST_FOO, &STATIC_1, &STATI
8068

8169
error: aborting due to 10 previous errors
8270

83-
Some errors have detailed explanations: E0161, E0277.
71+
Some errors have detailed explanations: E0161, E0277, E0507.
8472
For more information about an error, try `rustc --explain E0161`.

‎tests/ui/consts/const_refs_to_static-ice-121413.rs

-2
Original file line numberDiff line numberDiff line change
@@ -9,11 +9,9 @@ const REF_INTERIOR_MUT: &usize = {
99
//~^ ERROR failed to resolve: use of undeclared type `AtomicUsize`
1010
//~| WARN trait objects without an explicit `dyn` are deprecated
1111
//~| ERROR the size for values of type `(dyn Sync + 'static)` cannot be known at compilation time
12-
//~| ERROR the size for values of type `(dyn Sync + 'static)` cannot be known at compilation time
1312
//~| WARN this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
1413
//~| HELP if this is a dyn-compatible trait, use `dyn`
1514
//~| HELP the trait `Sized` is not implemented for `(dyn Sync + 'static)`
16-
//~| HELP the trait `Sized` is not implemented for `(dyn Sync + 'static)`
1715
unsafe { &*(&FOO as *const _ as *const usize) }
1816
};
1917
pub fn main() {}

‎tests/ui/consts/const_refs_to_static-ice-121413.stderr

+1-10
Original file line numberDiff line numberDiff line change
@@ -31,16 +31,7 @@ LL | static FOO: Sync = AtomicUsize::new(0);
3131
|
3232
= help: the trait `Sized` is not implemented for `(dyn Sync + 'static)`
3333

34-
error[E0277]: the size for values of type `(dyn Sync + 'static)` cannot be known at compilation time
35-
--> $DIR/const_refs_to_static-ice-121413.rs:8:24
36-
|
37-
LL | static FOO: Sync = AtomicUsize::new(0);
38-
| ^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
39-
|
40-
= help: the trait `Sized` is not implemented for `(dyn Sync + 'static)`
41-
= note: constant expressions must have a statically known size
42-
43-
error: aborting due to 3 previous errors; 1 warning emitted
34+
error: aborting due to 2 previous errors; 1 warning emitted
4435

4536
Some errors have detailed explanations: E0277, E0433.
4637
For more information about an error, try `rustc --explain E0277`.

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