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Rollup merge of #137218 - lukas-code:layout_of_cleanup, r=compiler-errors

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misc `layout_of` cleanup

See individual commits for details.

r? `@oli-obk` but feel free to reassign
This commit is contained in:
Matthias Krüger 2025-02-18 18:40:55 +01:00 committed by GitHub
commit bafff1b3af
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GPG Key ID: B5690EEEBB952194
8 changed files with 175 additions and 105 deletions
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28
compiler/rustc_middle/messages.ftl
View File

@ -37,9 +37,6 @@ middle_autodiff_unsafe_inner_const_ref = reading from a `Duplicated` const {$ty}
middle_bounds_check =
index out of bounds: the length is {$len} but the index is {$index}
middle_cannot_be_normalized =
unable to determine layout for `{$ty}` because `{$failure_ty}` cannot be normalized
middle_conflict_types =
this expression supplies two conflicting concrete types for the same opaque type
@ -52,9 +49,6 @@ middle_const_eval_non_int =
middle_const_not_used_in_type_alias =
const parameter `{$ct}` is part of concrete type but not used in parameter list for the `impl Trait` type alias
middle_cycle =
a cycle occurred during layout computation
middle_deprecated = use of deprecated {$kind} `{$path}`{$has_note ->
[true] : {$note}
*[other] {""}
@ -78,9 +72,23 @@ middle_erroneous_constant = erroneous constant encountered
middle_failed_writing_file =
failed to write file {$path}: {$error}"
middle_layout_cycle =
a cycle occurred during layout computation
middle_layout_normalization_failure =
unable to determine layout for `{$ty}` because `{$failure_ty}` cannot be normalized
middle_layout_references_error =
the type has an unknown layout
middle_layout_size_overflow =
values of the type `{$ty}` are too big for the target architecture
middle_layout_too_generic = the type `{$ty}` does not have a fixed layout
middle_layout_unknown =
the type `{$ty}` has an unknown layout
middle_opaque_hidden_type_mismatch =
concrete type differs from previous defining opaque type use
.label = expected `{$self_ty}`, got `{$other_ty}`
@ -98,16 +106,8 @@ middle_strict_coherence_needs_negative_coherence =
to use `strict_coherence` on this trait, the `with_negative_coherence` feature must be enabled
.label = due to this attribute
middle_too_generic = `{$ty}` does not have a fixed size
middle_type_length_limit = reached the type-length limit while instantiating `{$shrunk}`
middle_unknown_layout =
the type `{$ty}` has an unknown layout
middle_unsupported_union = we don't support unions yet: '{$ty_name}'
middle_values_too_big =
values of the type `{$ty}` are too big for the target architecture
middle_written_to_path = the full type name has been written to '{$path}'

10
compiler/rustc_middle/src/error.rs
View File

@ -132,19 +132,19 @@ impl fmt::Debug for CustomSubdiagnostic<'_> {
#[derive(Diagnostic)]
pub enum LayoutError<'tcx> {
#[diag(middle_unknown_layout)]
#[diag(middle_layout_unknown)]
Unknown { ty: Ty<'tcx> },
#[diag(middle_too_generic)]
#[diag(middle_layout_too_generic)]
TooGeneric { ty: Ty<'tcx> },
#[diag(middle_values_too_big)]
#[diag(middle_layout_size_overflow)]
Overflow { ty: Ty<'tcx> },
#[diag(middle_cannot_be_normalized)]
#[diag(middle_layout_normalization_failure)]
NormalizationFailure { ty: Ty<'tcx>, failure_ty: String },
#[diag(middle_cycle)]
#[diag(middle_layout_cycle)]
Cycle,
#[diag(middle_layout_references_error)]

33
compiler/rustc_middle/src/ty/layout.rs
View File

@ -229,11 +229,32 @@ impl fmt::Display for ValidityRequirement {
#[derive(Copy, Clone, Debug, HashStable, TyEncodable, TyDecodable)]
pub enum LayoutError<'tcx> {
/// A type doesn't have a sensible layout.
///
/// This variant is used for layout errors that don't necessarily cause
/// compile errors.
///
/// For example, this can happen if a struct contains an unsized type in a
/// non-tail field, but has an unsatisfiable bound like `str: Sized`.
Unknown(Ty<'tcx>),
/// The size of a type exceeds [`TargetDataLayout::obj_size_bound`].
SizeOverflow(Ty<'tcx>),
/// The layout can vary due to a generic parameter.
///
/// Unlike `Unknown`, this variant is a "soft" error and indicates that the layout
/// may become computable after further instantiating the generic parameter(s).
TooGeneric(Ty<'tcx>),
/// An alias failed to normalize.
///
/// This variant is necessary, because, due to trait solver incompleteness, it is
/// possible than an alias that was rigid during analysis fails to normalize after
/// revealing opaque types.
///
/// See `tests/ui/layout/normalization-failure.rs` for an example.
NormalizationFailure(Ty<'tcx>, NormalizationError<'tcx>),
/// A non-layout error is reported elsewhere.
ReferencesError(ErrorGuaranteed),
/// A type has cyclic layout, i.e. the type contains itself without indirection.
Cycle(ErrorGuaranteed),
}
@ -243,11 +264,11 @@ impl<'tcx> LayoutError<'tcx> {
use crate::fluent_generated::*;
match self {
Unknown(_) => middle_unknown_layout,
SizeOverflow(_) => middle_values_too_big,
TooGeneric(_) => middle_too_generic,
NormalizationFailure(_, _) => middle_cannot_be_normalized,
Cycle(_) => middle_cycle,
Unknown(_) => middle_layout_unknown,
SizeOverflow(_) => middle_layout_size_overflow,
TooGeneric(_) => middle_layout_too_generic,
NormalizationFailure(_, _) => middle_layout_normalization_failure,
Cycle(_) => middle_layout_cycle,
ReferencesError(_) => middle_layout_references_error,
}
}
@ -276,7 +297,7 @@ impl<'tcx> fmt::Display for LayoutError<'tcx> {
match *self {
LayoutError::Unknown(ty) => write!(f, "the type `{ty}` has an unknown layout"),
LayoutError::TooGeneric(ty) => {
write!(f, "`{ty}` does not have a fixed size")
write!(f, "the type `{ty}` does not have a fixed layout")
}
LayoutError::SizeOverflow(ty) => {
write!(f, "values of the type `{ty}` are too big for the target architecture")

127
compiler/rustc_ty_utils/src/layout.rs
View File

@ -134,42 +134,32 @@ fn univariant_uninterned<'tcx>(
cx: &LayoutCx<'tcx>,
ty: Ty<'tcx>,
fields: &IndexSlice<FieldIdx, TyAndLayout<'tcx>>,
repr: &ReprOptions,
kind: StructKind,
) -> Result<LayoutData<FieldIdx, VariantIdx>, &'tcx LayoutError<'tcx>> {
let pack = repr.pack;
if pack.is_some() && repr.align.is_some() {
cx.tcx().dcx().bug("struct cannot be packed and aligned");
}
cx.calc.univariant(fields, repr, kind).map_err(|err| map_error(cx, ty, err))
let repr = ReprOptions::default();
cx.calc.univariant(fields, &repr, kind).map_err(|err| map_error(cx, ty, err))
}
fn extract_const_value<'tcx>(
const_: ty::Const<'tcx>,
ty: Ty<'tcx>,
cx: &LayoutCx<'tcx>,
ty: Ty<'tcx>,
ct: ty::Const<'tcx>,
) -> Result<ty::Value<'tcx>, &'tcx LayoutError<'tcx>> {
match const_.kind() {
match ct.kind() {
ty::ConstKind::Value(cv) => Ok(cv),
ty::ConstKind::Error(guar) => {
return Err(error(cx, LayoutError::ReferencesError(guar)));
}
ty::ConstKind::Param(_) | ty::ConstKind::Expr(_) => {
if !const_.has_param() {
bug!("no generic type found in the type: {ty:?}");
ty::ConstKind::Param(_) | ty::ConstKind::Expr(_) | ty::ConstKind::Unevaluated(_) => {
if !ct.has_param() {
bug!("failed to normalize const, but it is not generic: {ct:?}");
}
return Err(error(cx, LayoutError::TooGeneric(ty)));
Err(error(cx, LayoutError::TooGeneric(ty)))
}
ty::ConstKind::Unevaluated(_) => {
if !const_.has_param() {
return Err(error(cx, LayoutError::Unknown(ty)));
} else {
return Err(error(cx, LayoutError::TooGeneric(ty)));
}
}
ty::ConstKind::Infer(_) | ty::ConstKind::Bound(..) | ty::ConstKind::Placeholder(_) => {
bug!("unexpected type: {ty:?}");
ty::ConstKind::Infer(_)
| ty::ConstKind::Bound(..)
| ty::ConstKind::Placeholder(_)
| ty::ConstKind::Error(_) => {
// `ty::ConstKind::Error` is handled at the top of `layout_of_uncached`
// (via `ty.error_reported()`).
bug!("layout_of: unexpected const: {ct:?}");
}
}
}
@ -194,10 +184,9 @@ fn layout_of_uncached<'tcx>(
};
let scalar = |value: Primitive| tcx.mk_layout(LayoutData::scalar(cx, scalar_unit(value)));
let univariant =
|fields: &IndexSlice<FieldIdx, TyAndLayout<'tcx>>, repr: &ReprOptions, kind| {
Ok(tcx.mk_layout(univariant_uninterned(cx, ty, fields, repr, kind)?))
};
let univariant = |fields: &IndexSlice<FieldIdx, TyAndLayout<'tcx>>, kind| {
Ok(tcx.mk_layout(univariant_uninterned(cx, ty, fields, kind)?))
};
debug_assert!(!ty.has_non_region_infer());
Ok(match *ty.kind() {
@ -210,12 +199,12 @@ fn layout_of_uncached<'tcx>(
&mut layout.backend_repr
{
if let Some(start) = start {
scalar.valid_range_mut().start = extract_const_value(start, ty, cx)?
scalar.valid_range_mut().start = extract_const_value(cx, ty, start)?
.try_to_bits(tcx, cx.typing_env)
.ok_or_else(|| error(cx, LayoutError::Unknown(ty)))?;
}
if let Some(end) = end {
let mut end = extract_const_value(end, ty, cx)?
let mut end = extract_const_value(cx, ty, end)?
.try_to_bits(tcx, cx.typing_env)
.ok_or_else(|| error(cx, LayoutError::Unknown(ty)))?;
if !include_end {
@ -274,16 +263,11 @@ fn layout_of_uncached<'tcx>(
data_ptr.valid_range_mut().start = 1;
}
let pointee = tcx.normalize_erasing_regions(cx.typing_env, pointee);
if pointee.is_sized(tcx, cx.typing_env) {
return Ok(tcx.mk_layout(LayoutData::scalar(cx, data_ptr)));
}
let metadata = if let Some(metadata_def_id) = tcx.lang_items().metadata_type()
// Projection eagerly bails out when the pointee references errors,
// fall back to structurally deducing metadata.
&& !pointee.references_error()
{
let metadata = if let Some(metadata_def_id) = tcx.lang_items().metadata_type() {
let pointee_metadata = Ty::new_projection(tcx, metadata_def_id, [pointee]);
let metadata_ty =
match tcx.try_normalize_erasing_regions(cx.typing_env, pointee_metadata) {
@ -354,7 +338,7 @@ fn layout_of_uncached<'tcx>(
// Arrays and slices.
ty::Array(element, count) => {
let count = extract_const_value(count, ty, cx)?
let count = extract_const_value(cx, ty, count)?
.try_to_target_usize(tcx)
.ok_or_else(|| error(cx, LayoutError::Unknown(ty)))?;
@ -415,17 +399,10 @@ fn layout_of_uncached<'tcx>(
}),
// Odd unit types.
ty::FnDef(..) => {
univariant(IndexSlice::empty(), &ReprOptions::default(), StructKind::AlwaysSized)?
}
ty::FnDef(..) => univariant(IndexSlice::empty(), StructKind::AlwaysSized)?,
ty::Dynamic(_, _, ty::Dyn) | ty::Foreign(..) => {
let mut unit = univariant_uninterned(
cx,
ty,
IndexSlice::empty(),
&ReprOptions::default(),
StructKind::AlwaysSized,
)?;
let mut unit =
univariant_uninterned(cx, ty, IndexSlice::empty(), StructKind::AlwaysSized)?;
match unit.backend_repr {
BackendRepr::Memory { ref mut sized } => *sized = false,
_ => bug!(),
@ -439,7 +416,6 @@ fn layout_of_uncached<'tcx>(
let tys = args.as_closure().upvar_tys();
univariant(
&tys.iter().map(|ty| cx.layout_of(ty)).try_collect::<IndexVec<_, _>>()?,
&ReprOptions::default(),
StructKind::AlwaysSized,
)?
}
@ -448,7 +424,6 @@ fn layout_of_uncached<'tcx>(
let tys = args.as_coroutine_closure().upvar_tys();
univariant(
&tys.iter().map(|ty| cx.layout_of(ty)).try_collect::<IndexVec<_, _>>()?,
&ReprOptions::default(),
StructKind::AlwaysSized,
)?
}
@ -457,11 +432,7 @@ fn layout_of_uncached<'tcx>(
let kind =
if tys.len() == 0 { StructKind::AlwaysSized } else { StructKind::MaybeUnsized };
univariant(
&tys.iter().map(|k| cx.layout_of(k)).try_collect::<IndexVec<_, _>>()?,
&ReprOptions::default(),
kind,
)?
univariant(&tys.iter().map(|k| cx.layout_of(k)).try_collect::<IndexVec<_, _>>()?, kind)?
}
// SIMD vector types.
@ -719,25 +690,30 @@ fn layout_of_uncached<'tcx>(
}
// Types with no meaningful known layout.
ty::Alias(..) => {
if ty.has_param() {
return Err(error(cx, LayoutError::TooGeneric(ty)));
}
// NOTE(eddyb) `layout_of` query should've normalized these away,
// if that was possible, so there's no reason to try again here.
return Err(error(cx, LayoutError::Unknown(ty)));
}
ty::Bound(..) | ty::CoroutineWitness(..) | ty::Infer(_) | ty::Error(_) => {
bug!("Layout::compute: unexpected type `{}`", ty)
}
ty::Param(_) => {
return Err(error(cx, LayoutError::TooGeneric(ty)));
}
ty::Placeholder(..) => {
return Err(error(cx, LayoutError::Unknown(ty)));
ty::Alias(..) => {
// NOTE(eddyb) `layout_of` query should've normalized these away,
// if that was possible, so there's no reason to try again here.
let err = if ty.has_param() {
LayoutError::TooGeneric(ty)
} else {
// This is only reachable with unsatisfiable predicates. For example, if we have
// `u8: Iterator`, then we can't compute the layout of `<u8 as Iterator>::Item`.
LayoutError::Unknown(ty)
};
return Err(error(cx, err));
}
ty::Placeholder(..)
| ty::Bound(..)
| ty::CoroutineWitness(..)
| ty::Infer(_)
| ty::Error(_) => {
// `ty::Error` is handled at the top of this function.
bug!("layout_of: unexpected type `{ty}`")
}
})
}
@ -911,13 +887,7 @@ fn coroutine_layout<'tcx>(
.chain(iter::once(Ok(tag_layout)))
.chain(promoted_layouts)
.try_collect::<IndexVec<_, _>>()?;
let prefix = univariant_uninterned(
cx,
ty,
&prefix_layouts,
&ReprOptions::default(),
StructKind::AlwaysSized,
)?;
let prefix = univariant_uninterned(cx, ty, &prefix_layouts, StructKind::AlwaysSized)?;
let (prefix_size, prefix_align) = (prefix.size, prefix.align);
@ -982,7 +952,6 @@ fn coroutine_layout<'tcx>(
cx,
ty,
&variant_only_tys.map(|ty| cx.layout_of(ty)).try_collect::<IndexVec<_, _>>()?,
&ReprOptions::default(),
StructKind::Prefixed(prefix_size, prefix_align.abi),
)?;
variant.variants = Variants::Single { index };

5
tests/ui/layout/debug.rs
View File

@ -82,3 +82,8 @@ type Impossible = (str, str); //~ ERROR: cannot be known at compilation time
#[rustc_layout(debug)]
union EmptyUnion {} //~ ERROR: has an unknown layout
//~^ ERROR: unions cannot have zero fields
// Test the error message of `LayoutError::TooGeneric`
// (this error is never emitted to users).
#[rustc_layout(debug)]
type TooGeneric<T> = T; //~ ERROR: does not have a fixed layout

8
tests/ui/layout/debug.stderr
View File

@ -596,12 +596,18 @@ error: the type has an unknown layout
LL | union EmptyUnion {}
| ^^^^^^^^^^^^^^^^
error: the type `T` does not have a fixed layout
--> $DIR/debug.rs:89:1
|
LL | type TooGeneric<T> = T;
| ^^^^^^^^^^^^^^^^^^
error: `#[rustc_layout]` can only be applied to `struct`/`enum`/`union` declarations and type aliases
--> $DIR/debug.rs:75:5
|
LL | const C: () = ();
| ^^^^^^^^^^^
error: aborting due to 19 previous errors
error: aborting due to 20 previous errors
For more information about this error, try `rustc --explain E0277`.

57
tests/ui/layout/normalization-failure.rs Normal file
View File

@ -0,0 +1,57 @@
//! This test demonstrates how `LayoutError::NormalizationFailure` can happen and why
//! it is necessary.
//!
//! This code does not cause an immediate normalization error in typeck, because we
//! don't reveal the hidden type returned by `opaque<T>` in the analysis typing mode.
//! Instead, `<{opaque} as Project2>::Assoc2` is a *rigid projection*, because we know
//! that `{opaque}: Project2` holds, due to the opaque type's `impl Project2` bound,
//! but cannot normalize `<{opaque} as Project2>::Assoc2` any further.
//!
//! However, in the post-analysis typing mode, which is used for the layout computation,
//! the opaque's hidden type is revealed to be `PhantomData<T>`, and now we fail to
//! normalize `<PhantomData<T> as Project2>::Assoc2` if there is a `T: Project1` bound
//! in the param env! This happens, because `PhantomData<T>: Project2` only holds if
//! `<T as Project1>::Assoc1 == ()` holds. This would usually be satisfied by the
//! blanket `impl<T> Project1 for T`, but due to the `T: Project1` bound we do not
//! normalize `<T as Project1>::Assoc1` via the impl and treat it as rigid instead.
//! Therefore, `PhantomData<T>: Project2` does NOT hold and normalizing
//! `<PhantomData<T> as Project2>::Assoc2` fails.
//!
//! Note that this layout error can only happen when computing the layout in a generic
//! context, which is not required for codegen, but may happen for lints, MIR optimizations,
//! and the transmute check.
use std::marker::PhantomData;
trait Project1 {
type Assoc1;
}
impl<T> Project1 for T {
type Assoc1 = ();
}
trait Project2 {
type Assoc2;
fn get(self) -> Self::Assoc2;
}
impl<T: Project1<Assoc1 = ()>> Project2 for PhantomData<T> {
type Assoc2 = ();
fn get(self) -> Self::Assoc2 {}
}
fn opaque<T>() -> impl Project2 {
PhantomData::<T>
}
fn check<T: Project1>() {
unsafe {
std::mem::transmute::<_, ()>(opaque::<T>().get());
//~^ ERROR: cannot transmute
//~| NOTE: (unable to determine layout for `<impl Project2 as Project2>::Assoc2` because `<impl Project2 as Project2>::Assoc2` cannot be normalized)
//~| NOTE: (0 bits)
}
}
fn main() {}

12
tests/ui/layout/normalization-failure.stderr Normal file
View File

@ -0,0 +1,12 @@
error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
--> $DIR/normalization-failure.rs:50:9
|
LL | std::mem::transmute::<_, ()>(opaque::<T>().get());
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: source type: `<impl Project2 as Project2>::Assoc2` (unable to determine layout for `<impl Project2 as Project2>::Assoc2` because `<impl Project2 as Project2>::Assoc2` cannot be normalized)
= note: target type: `()` (0 bits)
error: aborting due to 1 previous error
For more information about this error, try `rustc --explain E0512`.