bjoernager/rust
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get rid of an old hack

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For structs that cannot be unsized, the layout algorithm sometimes moves
unsized fields to the end of the struct, which circumvented the error
for unexpected unsized fields and returned an unsized layout anyway.

This commit makes it so that the unexpected unsized error is always
returned for structs that cannot be unsized, allowing us to remove an
old hack and fixing some old ICE.
This commit is contained in:
Lukas Markeffsky 2024-09-16 21:37:40 +02:00
parent 3db930a463
commit 20d2414925
6 changed files with 55 additions and 50 deletions
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41
compiler/rustc_ty_utils/src/layout.rs
View file

@ -13,8 +13,7 @@ use rustc_middle::ty::layout::{
};
use rustc_middle::ty::print::with_no_trimmed_paths;
use rustc_middle::ty::{
self, AdtDef, CoroutineArgsExt, EarlyBinder, FieldDef, GenericArgsRef, Ty, TyCtxt,
TypeVisitableExt,
self, AdtDef, CoroutineArgsExt, EarlyBinder, GenericArgsRef, Ty, TyCtxt, TypeVisitableExt,
};
use rustc_session::{DataTypeKind, FieldInfo, FieldKind, SizeKind, VariantInfo};
use rustc_span::sym;
@ -572,40 +571,6 @@ fn layout_of_uncached<'tcx>(
));
}
let err_if_unsized = |field: &FieldDef, err_msg: &str| {
let field_ty = tcx.type_of(field.did);
let is_unsized = tcx
.try_instantiate_and_normalize_erasing_regions(args, cx.param_env, field_ty)
.map(|f| !f.is_sized(tcx, cx.param_env))
.map_err(|e| {
error(
cx,
LayoutError::NormalizationFailure(field_ty.instantiate_identity(), e),
)
})?;
if is_unsized {
tcx.dcx().span_delayed_bug(tcx.def_span(def.did()), err_msg.to_owned());
Err(error(cx, LayoutError::Unknown(ty)))
} else {
Ok(())
}
};
if def.is_struct() {
if let Some((_, fields_except_last)) =
def.non_enum_variant().fields.raw.split_last()
{
for f in fields_except_last {
err_if_unsized(f, "only the last field of a struct can be unsized")?;
}
}
} else {
for f in def.all_fields() {
err_if_unsized(f, &format!("{}s cannot have unsized fields", def.descr()))?;
}
}
let get_discriminant_type =
|min, max| Integer::repr_discr(tcx, ty, &def.repr(), min, max);
@ -643,6 +608,10 @@ fn layout_of_uncached<'tcx>(
)
.map_err(|err| map_error(cx, ty, err))?;
if !maybe_unsized && layout.is_unsized() {
bug!("got unsized layout for type that cannot be unsized {ty:?}: {layout:#?}");
}
// If the struct tail is sized and can be unsized, check that unsizing doesn't move the fields around.
if cfg!(debug_assertions)
&& maybe_unsized