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gurrygurry
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Error out of layout calculation if a non-last struct field is unsized
Fixes an ICE that occurs when a struct with an unsized field at a non-last position is const evaluated.
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3 files changed

+222
-1
lines changed

3 files changed

+222
-1
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‎compiler/rustc_ty_utils/src/layout.rs

+37-1
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,9 @@ use rustc_middle::ty::layout::{
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IntegerExt, LayoutCx, LayoutError, LayoutOf, TyAndLayout, MAX_SIMD_LANES,
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};
1010
use rustc_middle::ty::print::with_no_trimmed_paths;
11-
use rustc_middle::ty::{self, AdtDef, EarlyBinder, GenericArgsRef, Ty, TyCtxt, TypeVisitableExt};
11+
use rustc_middle::ty::{
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self, AdtDef, EarlyBinder, FieldDef, GenericArgsRef, Ty, TyCtxt, TypeVisitableExt,
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};
1214
use rustc_session::{DataTypeKind, FieldInfo, FieldKind, SizeKind, VariantInfo};
1315
use rustc_span::sym;
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use rustc_span::symbol::Symbol;
@@ -506,6 +508,40 @@ fn layout_of_uncached<'tcx>(
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));
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}
508510

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let err_if_unsized = |field: &FieldDef, err_msg: &str| {
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let field_ty = tcx.type_of(field.did);
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let is_unsized = tcx
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.try_instantiate_and_normalize_erasing_regions(args, cx.param_env, field_ty)
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.map(|f| !f.is_sized(tcx, cx.param_env))
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.map_err(|e| {
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error(
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cx,
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LayoutError::NormalizationFailure(field_ty.instantiate_identity(), e),
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)
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})?;
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if is_unsized {
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cx.tcx.dcx().span_delayed_bug(tcx.def_span(def.did()), err_msg.to_owned());
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Err(error(cx, LayoutError::Unknown(ty)))
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} else {
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Ok(())
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}
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};
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if def.is_struct() {
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if let Some((_, fields_except_last)) =
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def.non_enum_variant().fields.raw.split_last()
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{
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for f in fields_except_last {
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err_if_unsized(f, "only the last field of a struct can be unsized")?;
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}
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}
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} else {
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for f in def.all_fields() {
541+
err_if_unsized(f, &format!("{}s cannot have unsized fields", def.descr()))?;
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}
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}
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509545
let get_discriminant_type =
510546
|min, max| Integer::repr_discr(tcx, ty, &def.repr(), min, max);
511547

‎tests/ui/layout/ice-non-last-unsized-field-issue-121473.rs

+79
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,79 @@
1+
// Regression test for #121473
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// Checks that no ICE occurs when `size_of`
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// is applied to a struct that has an unsized
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// field which is not its last field
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use std::mem::size_of;
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pub struct BadStruct {
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pub field1: i32,
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pub field2: str, // Unsized field that is not the last field
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//~^ ERROR the size for values of type `str` cannot be known at compilation time
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pub field3: [u8; 16],
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}
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enum BadEnum1 {
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Variant1 {
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field1: i32,
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field2: str, // Unsized
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//~^ ERROR the size for values of type `str` cannot be known at compilation time
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field3: [u8; 16],
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},
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}
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enum BadEnum2 {
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Variant1(
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i32,
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str, // Unsized
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//~^ ERROR the size for values of type `str` cannot be known at compilation time
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[u8; 16]
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),
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}
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enum BadEnumMultiVariant {
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Variant1(i32),
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Variant2 {
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field1: i32,
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field2: str, // Unsized
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//~^ ERROR the size for values of type `str` cannot be known at compilation time
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field3: [u8; 16],
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},
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Variant3
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}
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union BadUnion {
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field1: i32,
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field2: str, // Unsized
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//~^ ERROR the size for values of type `str` cannot be known at compilation time
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//~| ERROR field must implement `Copy` or be wrapped in `ManuallyDrop<...>` to be used in a union
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field3: [u8; 16],
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}
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// Used to test that projection type fields that normalize
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// to a sized type do not cause problems
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struct StructWithProjections<'a>
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{
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field1: <&'a [i32] as IntoIterator>::IntoIter,
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field2: i32
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}
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pub fn main() {
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let _a = &size_of::<BadStruct>();
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assert_eq!(size_of::<BadStruct>(), 21);
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64+
let _a = &size_of::<BadEnum1>();
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assert_eq!(size_of::<BadEnum1>(), 21);
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let _a = &size_of::<BadEnum2>();
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assert_eq!(size_of::<BadEnum2>(), 21);
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70+
let _a = &size_of::<BadEnumMultiVariant>();
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assert_eq!(size_of::<BadEnumMultiVariant>(), 21);
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let _a = &size_of::<BadUnion>();
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assert_eq!(size_of::<BadUnion>(), 21);
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76+
let _a = &size_of::<StructWithProjections>();
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assert_eq!(size_of::<StructWithProjections>(), 21);
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let _a = StructWithProjections { field1: [1, 3].iter(), field2: 3 };
79+
}

‎tests/ui/layout/ice-non-last-unsized-field-issue-121473.stderr

+106
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,106 @@
1+
error[E0277]: the size for values of type `str` cannot be known at compilation time
2+
--> $DIR/ice-non-last-unsized-field-issue-121473.rs:10:17
3+
|
4+
LL | pub field2: str, // Unsized field that is not the last field
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| ^^^ doesn't have a size known at compile-time
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|
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= help: the trait `Sized` is not implemented for `str`
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= note: only the last field of a struct may have a dynamically sized type
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= help: change the field's type to have a statically known size
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help: borrowed types always have a statically known size
11+
|
12+
LL | pub field2: &str, // Unsized field that is not the last field
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| +
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help: the `Box` type always has a statically known size and allocates its contents in the heap
15+
|
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LL | pub field2: Box<str>, // Unsized field that is not the last field
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| ++++ +
18+
19+
error[E0277]: the size for values of type `str` cannot be known at compilation time
20+
--> $DIR/ice-non-last-unsized-field-issue-121473.rs:18:17
21+
|
22+
LL | field2: str, // Unsized
23+
| ^^^ doesn't have a size known at compile-time
24+
|
25+
= help: the trait `Sized` is not implemented for `str`
26+
= note: no field of an enum variant may have a dynamically sized type
27+
= help: change the field's type to have a statically known size
28+
help: borrowed types always have a statically known size
29+
|
30+
LL | field2: &str, // Unsized
31+
| +
32+
help: the `Box` type always has a statically known size and allocates its contents in the heap
33+
|
34+
LL | field2: Box<str>, // Unsized
35+
| ++++ +
36+
37+
error[E0277]: the size for values of type `str` cannot be known at compilation time
38+
--> $DIR/ice-non-last-unsized-field-issue-121473.rs:27:9
39+
|
40+
LL | str, // Unsized
41+
| ^^^ doesn't have a size known at compile-time
42+
|
43+
= help: the trait `Sized` is not implemented for `str`
44+
= note: no field of an enum variant may have a dynamically sized type
45+
= help: change the field's type to have a statically known size
46+
help: borrowed types always have a statically known size
47+
|
48+
LL | &str, // Unsized
49+
| +
50+
help: the `Box` type always has a statically known size and allocates its contents in the heap
51+
|
52+
LL | Box<str>, // Unsized
53+
| ++++ +
54+
55+
error[E0277]: the size for values of type `str` cannot be known at compilation time
56+
--> $DIR/ice-non-last-unsized-field-issue-121473.rs:37:17
57+
|
58+
LL | field2: str, // Unsized
59+
| ^^^ doesn't have a size known at compile-time
60+
|
61+
= help: the trait `Sized` is not implemented for `str`
62+
= note: no field of an enum variant may have a dynamically sized type
63+
= help: change the field's type to have a statically known size
64+
help: borrowed types always have a statically known size
65+
|
66+
LL | field2: &str, // Unsized
67+
| +
68+
help: the `Box` type always has a statically known size and allocates its contents in the heap
69+
|
70+
LL | field2: Box<str>, // Unsized
71+
| ++++ +
72+
73+
error[E0277]: the size for values of type `str` cannot be known at compilation time
74+
--> $DIR/ice-non-last-unsized-field-issue-121473.rs:46:13
75+
|
76+
LL | field2: str, // Unsized
77+
| ^^^ doesn't have a size known at compile-time
78+
|
79+
= help: the trait `Sized` is not implemented for `str`
80+
= note: no field of a union may have a dynamically sized type
81+
= help: change the field's type to have a statically known size
82+
help: borrowed types always have a statically known size
83+
|
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LL | field2: &str, // Unsized
85+
| +
86+
help: the `Box` type always has a statically known size and allocates its contents in the heap
87+
|
88+
LL | field2: Box<str>, // Unsized
89+
| ++++ +
90+
91+
error[E0740]: field must implement `Copy` or be wrapped in `ManuallyDrop<...>` to be used in a union
92+
--> $DIR/ice-non-last-unsized-field-issue-121473.rs:46:5
93+
|
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LL | field2: str, // Unsized
95+
| ^^^^^^^^^^^
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|
97+
= note: union fields must not have drop side-effects, which is currently enforced via either `Copy` or `ManuallyDrop<...>`
98+
help: wrap the field type in `ManuallyDrop<...>`
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|
100+
LL | field2: std::mem::ManuallyDrop<str>, // Unsized
101+
| +++++++++++++++++++++++ +
102+
103+
error: aborting due to 6 previous errors
104+
105+
Some errors have detailed explanations: E0277, E0740.
106+
For more information about an error, try `rustc --explain E0277`.

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