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add helper method for finding the one non-1-ZST field

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This commit is contained in:
Ralf Jung 2023-09-12 20:51:00 +02:00
parent c41e7794cd
commit 72fb4b8f31
1 changed files with 6 additions and 13 deletions
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19
src/vtable.rs
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@ -48,19 +48,12 @@ pub(crate) fn get_ptr_and_method_ref<'tcx>(
) -> (Pointer, Value) {
let (ptr, vtable) = 'block: {
if let Abi::Scalar(_) = arg.layout().abi {
'descend_newtypes: while !arg.layout().ty.is_unsafe_ptr() && !arg.layout().ty.is_ref() {
for i in 0..arg.layout().fields.count() {
let field = arg.value_field(fx, FieldIdx::new(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
arg = field;
continue 'descend_newtypes;
}
}
bug!("receiver has no non-zero-sized fields {:?}", arg);
while !arg.layout().ty.is_unsafe_ptr() && !arg.layout().ty.is_ref() {
let (idx, _) = arg
.layout()
.non_1zst_field(fx)
.expect("not exactly one non-1-ZST field in a `DispatchFromDyn` type");
arg = arg.value_field(fx, FieldIdx::new(idx));
}
}