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Rollup merge of #115798 - RalfJung:non_1zst_field, r=wesleywiser

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add helper method for finding the one non-1-ZST field
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Matthias Krüger 2023-09-13 18:37:42 +02:00 • committed by GitHub
commit 565b9c2264
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5 changed files with 49 additions and 89 deletions
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41
compiler/rustc_codegen_ssa/src/mir/block.rs
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@ -928,21 +928,11 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
// we get a value of a built-in pointer type.
//
// This is also relevant for `Pin<&mut Self>`, where we need to peel the `Pin`.
'descend_newtypes: while !op.layout.ty.is_unsafe_ptr()
&& !op.layout.ty.is_ref()
{
for i in 0..op.layout.fields.count() {
let field = op.extract_field(bx, i);
if !field.layout.is_1zst() {
// we found the one non-1-ZST field that is allowed
// now find *its* non-zero-sized field, or stop if it's a
// pointer
op = field;
continue 'descend_newtypes;
}
}
span_bug!(span, "receiver has no non-zero-sized fields {:?}", op);
while !op.layout.ty.is_unsafe_ptr() && !op.layout.ty.is_ref() {
let (idx, _) = op.layout.non_1zst_field(bx).expect(
"not exactly one non-1-ZST field in a `DispatchFromDyn` type",
);
op = op.extract_field(bx, idx);
}
// now that we have `*dyn Trait` or `&dyn Trait`, split it up into its
@ -970,22 +960,11 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
}
Immediate(_) => {
// See comment above explaining why we peel these newtypes
'descend_newtypes: while !op.layout.ty.is_unsafe_ptr()
&& !op.layout.ty.is_ref()
{
for i in 0..op.layout.fields.count() {
let field = op.extract_field(bx, i);
if !field.layout.is_1zst() {
// We found the one non-1-ZST field that is allowed. (The rules
// for `DispatchFromDyn` ensure there's exactly one such field.)
// Now find *its* non-zero-sized field, or stop if it's a
// pointer.
op = field;
continue 'descend_newtypes;
}
}
span_bug!(span, "receiver has no non-zero-sized fields {:?}", op);
while !op.layout.ty.is_unsafe_ptr() && !op.layout.ty.is_ref() {
let (idx, _) = op.layout.non_1zst_field(bx).expect(
"not exactly one non-1-ZST field in a `DispatchFromDyn` type",
);
op = op.extract_field(bx, idx);
}
// Make sure that we've actually unwrapped the rcvr down