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Auto merge of #94527 - oli-obk:undef_scalars, r=nagisa,erikdesjardin

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Let CTFE to handle partially uninitialized unions without marking the entire value as uninitialized.

follow up to #94411

To fix https://github.com/rust-lang/rust/issues/69488 and by extension fix https://github.com/rust-lang/rust/issues/94371, we should stop treating types like `MaybeUninit<usize>` as something that the `Scalar` type in the interpreter engine can represent. So we add a new field to `abi::Primitive` that records whether the primitive is nested in a union

cc `@RalfJung`

r? `@ghost`
This commit is contained in:
bors 2022-04-05 16:46:13 +00:00
commit f262ca12aa
42 changed files with 466 additions and 333 deletions
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16
compiler/rustc_lint/src/types.rs
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@ -12,7 +12,7 @@ use rustc_middle::ty::{self, AdtKind, DefIdTree, Ty, TyCtxt, TypeFoldable};
use rustc_span::source_map;
use rustc_span::symbol::sym;
use rustc_span::{Span, Symbol, DUMMY_SP};
use rustc_target::abi::Abi;
use rustc_target::abi::{Abi, WrappingRange};
use rustc_target::abi::{Integer, TagEncoding, Variants};
use rustc_target::spec::abi::Abi as SpecAbi;
@ -796,14 +796,18 @@ crate fn repr_nullable_ptr<'tcx>(
// Return the nullable type this Option-like enum can be safely represented with.
let field_ty_abi = &cx.layout_of(field_ty).unwrap().abi;
if let Abi::Scalar(field_ty_scalar) = field_ty_abi {
match (field_ty_scalar.valid_range.start, field_ty_scalar.valid_range.end) {
(0, x) if x == field_ty_scalar.value.size(&cx.tcx).unsigned_int_max() - 1 => {
match field_ty_scalar.valid_range(cx) {
WrappingRange { start: 0, end }
if end == field_ty_scalar.size(&cx.tcx).unsigned_int_max() - 1 =>
{
return Some(get_nullable_type(cx, field_ty).unwrap());
}
(1, _) => {
WrappingRange { start: 1, .. } => {
return Some(get_nullable_type(cx, field_ty).unwrap());
}
(start, end) => unreachable!("Unhandled start and end range: ({}, {})", start, end),
WrappingRange { start, end } => {
unreachable!("Unhandled start and end range: ({}, {})", start, end)
}
};
}
}
@ -1342,7 +1346,7 @@ impl<'tcx> LateLintPass<'tcx> for VariantSizeDifferences {
return
};
let tag_size = tag.value.size(&cx.tcx).bytes();
let tag_size = tag.size(&cx.tcx).bytes();
debug!(
"enum `{}` is {} bytes large with layout:\n{:#?}",