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Change tag_field to FieldIdx in Variants::Multiple

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It was already available as a generic parameter anyway, and it's not like we'll ever put a tag in the 5-billionth field.
This commit is contained in:
Scott McMurray
2025-06-03 23:42:21 -07:00
parent 792fc2b033
commit ee9901e65c
14 changed files with 33 additions and 31 deletions
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8
compiler/rustc_const_eval/src/interpret/discriminant.rs
View File

@@ -1,6 +1,6 @@
//! Functions for reading and writing discriminants of multi-variant layouts (enums and coroutines).
use rustc_abi::{self as abi, TagEncoding, VariantIdx, Variants};
use rustc_abi::{self as abi, FieldIdx, TagEncoding, VariantIdx, Variants};
use rustc_middle::ty::layout::{LayoutOf, PrimitiveExt, TyAndLayout};
use rustc_middle::ty::{self, CoroutineArgsExt, ScalarInt, Ty};
use rustc_middle::{mir, span_bug};
@@ -26,7 +26,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
// No need to validate that the discriminant here because the
// `TyAndLayout::for_variant()` call earlier already checks the
// variant is valid.
let tag_dest = self.project_field(dest, tag_field)?;
let tag_dest = self.project_field(dest, tag_field.as_usize())?;
self.write_scalar(tag, &tag_dest)
}
None => {
@@ -96,7 +96,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
let tag_layout = self.layout_of(tag_scalar_layout.primitive().to_int_ty(*self.tcx))?;
// Read tag and sanity-check `tag_layout`.
let tag_val = self.read_immediate(&self.project_field(op, tag_field)?)?;
let tag_val = self.read_immediate(&self.project_field(op, tag_field.as_usize())?)?;
assert_eq!(tag_layout.size, tag_val.layout.size);
assert_eq!(tag_layout.backend_repr.is_signed(), tag_val.layout.backend_repr.is_signed());
trace!("tag value: {}", tag_val);
@@ -231,7 +231,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
&self,
layout: TyAndLayout<'tcx>,
variant_index: VariantIdx,
) -> InterpResult<'tcx, Option<(ScalarInt, usize)>> {
) -> InterpResult<'tcx, Option<(ScalarInt, FieldIdx)>> {
// Layout computation excludes uninhabited variants from consideration.
// Therefore, there's no way to represent those variants in the given layout.
// Essentially, uninhabited variants do not have a tag that corresponds to their

2
compiler/rustc_const_eval/src/interpret/validity.rs
View File

@@ -294,7 +294,7 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
// First, check if we are projecting to a variant.
match layout.variants {
Variants::Multiple { tag_field, .. } => {
if tag_field == field {
if tag_field.as_usize() == field {
return match layout.ty.kind() {
ty::Adt(def, ..) if def.is_enum() => PathElem::EnumTag,
ty::Coroutine(..) => PathElem::CoroutineTag,