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rust: pin-init: internal: init: use slot identifier directly with mixed site

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Use `quote_spanned!(Span::mixed_site() => ...)` directly instead of
creating `slot` identifier and interpolate it later. Do the same for
`__data`, too.

This is needed so that we can customize the location of the span without
having the `slot` identifier getting in the way. For example:

    quote_spanned!(Span::mixed_site().located_at(loc) => ...)

with `slot` mentioned directly will have the diagnostic pointing to the
desired location, while `#slot` won't.

Link: https://patch.msgid.link/20260916-dev-hygiene-v1-2-dfb6ae2588ba@garyguo.net
Signed-off-by: Gary Guo <gary@garyguo.net>
This commit is contained in:
Gary Guo 2026-09-16 13:11:33 +01:00
parent e30decc3f9
commit 7f849c19e2
1 changed files with 12 additions and 19 deletions
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31
rust/pin-init/internal/src/init.rs
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@ -269,7 +269,6 @@ fn expand(
},
|(_, err)| Box::new(err),
);
let slot = Ident::new("slot", Span::mixed_site());
let (has_data_trait, get_data, init_from_closure) = if pinned {
(
format_ident!("HasPinData"),
@ -286,7 +285,7 @@ fn expand(
let init_kind = get_init_kind(rest, dcx);
let zeroable_check = match init_kind {
InitKind::Normal => quote!(),
InitKind::Zeroing => quote! {
InitKind::Zeroing => quote_spanned! { Span::mixed_site() =>
// The user specified `..Zeroable::zeroed()` at the end of the list of fields.
// Therefore we check if the struct implements `Zeroable` and then zero the memory.
// This allows us to also remove the check that all fields are present (since we
@ -295,9 +294,9 @@ fn assert_zeroable<T: ?::core::marker::Sized>(_: *mut T)
where T: ::pin_init::Zeroable
{}
// Ensure that the struct is indeed `Zeroable`.
assert_zeroable(#slot);
assert_zeroable(slot);
// SAFETY: The type implements `Zeroable` by the check above.
unsafe { ::core::ptr::write_bytes(#slot, 0, 1) };
unsafe { ::core::ptr::write_bytes(slot, 0, 1) };
},
};
let this = match this {
@ -309,20 +308,19 @@ fn assert_zeroable<T: ?::core::marker::Sized>(_: *mut T)
},
};
// `mixed_site` ensures that the data is not accessible to the user-controlled code.
let data = Ident::new("__data", Span::mixed_site());
let init_fields = init_fields(&fields, pinned, &data, &slot);
let init_fields = init_fields(&fields, pinned);
let field_check = make_field_check(&fields, init_kind, &path);
Ok(quote_spanned! { Span::mixed_site() => {
// Get the data about fields from the supplied type.
// SAFETY: TODO
let #data = unsafe {
let data = unsafe {
use ::pin_init::__internal::#has_data_trait;
// Can't use `<#path as #has_data_trait>::#get_data`, since the user is able to omit
// generics (which need to be present with that syntax).
#path::#get_data()
};
// Ensure that `#data` really is of type `#data` and help with type inference:
let init = #data.__make_closure::<_, #error>(
// Ensure that `data` really is of type `data` and help with type inference:
let init = data.__make_closure::<_, #error>(
move |slot| {
#zeroable_check
#this
@ -380,12 +378,7 @@ fn get_init_kind(rest: Option<(Token![..], Expr)>, dcx: &mut DiagCtxt) -> InitKi
}
/// Generate the code that initializes the fields of the struct using the initializers in `field`.
fn init_fields(
fields: &Punctuated<InitializerField, Token![,]>,
pinned: bool,
data: &Ident,
slot: &Ident,
) -> TokenStream {
fn init_fields(fields: &Punctuated<InitializerField, Token![,]>, pinned: bool) -> TokenStream {
let mut guards = vec![];
let mut guard_attrs = vec![];
let mut res = TokenStream::new();
@ -413,16 +406,16 @@ fn init_fields(
let ident = member.as_ident();
let slot = if pinned {
quote! {
quote_spanned! { Span::mixed_site() =>
// SAFETY:
// - `slot` is valid and properly aligned.
// - `make_field_check` checks that `&raw mut (*slot).#member` is properly aligned.
// - `make_field_check` prevents `#member` from being used twice, therefore
// `(*slot).#member` is exclusively accessed and has not been initialized.
(unsafe { #data.#ident(#slot) })
(unsafe { data.#ident(slot) })
}
} else {
quote! {
quote_spanned! { Span::mixed_site() =>
// For `init!()` macro, everything is unpinned.
// SAFETY:
// - `&raw mut (*slot).#member` is valid.
@ -431,7 +424,7 @@ fn init_fields(
// `(*slot).#member` is exclusively accessed and has not been initialized.
(unsafe {
::pin_init::__internal::Slot::<::pin_init::__internal::Unpinned, _>::new(
&raw mut (*#slot).#member
&raw mut (*slot).#member
)
})
}