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Auto merge of #114208 - GKFX:offset_of_enum, r=wesleywiser

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Support enum variants in offset_of!

This MR implements support for navigating through enum variants in `offset_of!`, placing the enum variant name in the second argument to `offset_of!`. The RFC placed it in the first argument, but I think it interacts better with nested field access in the second, as you can then write things like

```rust
offset_of!(Type, field.Variant.field)
```

Alternatively, a syntactic distinction could be made between variants and fields (e.g. `field::Variant.field`) but I'm not convinced this would be helpful.

[RFC 3308 # Enum Support](https://rust-lang.github.io/rfcs/3308-offset_of.html#enum-support-offset_ofsomeenumstructvariant-field_on_variant)
Tracking Issue #106655.
This commit is contained in:
bors 2023-11-01 14:17:56 +00:00
commit 146dafa262
33 changed files with 477 additions and 89 deletions
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2
compiler/rustc_const_eval/src/interpret/step.rs
View file

@ -275,7 +275,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
mir::NullOp::SizeOf => layout.size.bytes(),
mir::NullOp::AlignOf => layout.align.abi.bytes(),
mir::NullOp::OffsetOf(fields) => {
layout.offset_of_subfield(self, fields.iter().map(|f| f.index())).bytes()
layout.offset_of_subfield(self, fields.iter()).bytes()
}
};
self.write_scalar(Scalar::from_target_usize(val, self), &dest)?;

23
compiler/rustc_const_eval/src/transform/validate.rs
View file

@ -1056,16 +1056,23 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
}
}
}
Rvalue::NullaryOp(NullOp::OffsetOf(fields), container) => {
Rvalue::NullaryOp(NullOp::OffsetOf(indices), container) => {
let fail_out_of_bounds = |this: &mut Self, location, field, ty| {
this.fail(location, format!("Out of bounds field {field:?} for {ty:?}"));
};
let mut current_ty = *container;
for field in fields.iter() {
for (variant, field) in indices.iter() {
match current_ty.kind() {
ty::Tuple(fields) => {
if variant != FIRST_VARIANT {
self.fail(
location,
format!("tried to get variant {variant:?} of tuple"),
);
return;
}
let Some(&f_ty) = fields.get(field.as_usize()) else {
fail_out_of_bounds(self, location, field, current_ty);
return;
@ -1074,15 +1081,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
current_ty = self.tcx.normalize_erasing_regions(self.param_env, f_ty);
}
ty::Adt(adt_def, args) => {
if adt_def.is_enum() {
self.fail(
location,
format!("Cannot get field offset from enum {current_ty:?}"),
);
return;
}
let Some(field) = adt_def.non_enum_variant().fields.get(field) else {
let Some(field) = adt_def.variant(variant).fields.get(field) else {
fail_out_of_bounds(self, location, field, current_ty);
return;
};
@ -1093,7 +1092,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
_ => {
self.fail(
location,
format!("Cannot get field offset from non-adt type {current_ty:?}"),
format!("Cannot get offset ({variant:?}, {field:?}) from type {current_ty:?}"),
);
return;
}