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rust: pin-init: internal: init: handle code blocks early

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`InitializerKind::Code` is a special case where it does not initialize a
field, and thus generate no guard and accessors. Handle it earlier and make
the rest of the code more linear.

Signed-off-by: Gary Guo <gary@garyguo.net>
This commit is contained in:
Gary Guo
2026-05-12 13:09:49 +01:00
parent fea304ec87
commit df1827babd
1 changed files with 55 additions and 45 deletions
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100
rust/pin-init/internal/src/init.rs
View File

@@ -231,6 +231,20 @@ fn init_fields(
cfgs.retain(|attr| attr.path().is_ident("cfg"));
cfgs
};
let ident = match kind {
InitializerKind::Value { ident, .. } => ident,
InitializerKind::Init { ident, .. } => ident,
InitializerKind::Code { block, .. } => {
res.extend(quote! {
#(#attrs)*
#[allow(unused_braces)]
#block
});
continue;
}
};
let init = match kind {
InitializerKind::Value { ident, value } => {
let mut value_ident = ident.clone();
@@ -283,55 +297,51 @@ fn init_fields(
}
}
}
InitializerKind::Code { block: value, .. } => quote! {
#(#attrs)*
#[allow(unused_braces)]
#value
},
InitializerKind::Code { .. } => unreachable!(),
};
res.extend(init);
if let Some(ident) = kind.ident() {
// `mixed_site` ensures that the guard is not accessible to the user-controlled code.
let guard = format_ident!("__{ident}_guard", span = Span::mixed_site());
// NOTE: The reference is derived from the guard so that it only lives as long as the
// guard does and cannot escape the scope. If it's created via `&mut (*#slot).#ident`
// like the unaligned field guard, it will become effectively `'static`.
let accessor = if pinned {
let project_ident = format_ident!("__project_{ident}");
quote! {
// SAFETY: the initialization is pinned.
unsafe { #data.#project_ident(#guard.let_binding()) }
}
} else {
quote! {
#guard.let_binding()
}
// `mixed_site` ensures that the guard is not accessible to the user-controlled code.
let guard = format_ident!("__{ident}_guard", span = Span::mixed_site());
// NOTE: The reference is derived from the guard so that it only lives as long as the
// guard does and cannot escape the scope. If it's created via `&mut (*#slot).#ident`
// like the unaligned field guard, it will become effectively `'static`.
let accessor = if pinned {
let project_ident = format_ident!("__project_{ident}");
quote! {
// SAFETY: the initialization is pinned.
unsafe { #data.#project_ident(#guard.let_binding()) }
}
} else {
quote! {
#guard.let_binding()
}
};
res.extend(quote! {
#init
#(#cfgs)*
// Create the drop guard.
//
// SAFETY:
// - `&raw mut (*slot).#ident` is valid.
// - `make_field_check` checks that `&raw mut (*slot).#ident` is properly aligned.
// - `(*slot).#ident` has been initialized above.
// - We only need the ownership to the pointee back when initialization has
// succeeded, where we `forget` the guard.
let mut #guard = unsafe {
::pin_init::__internal::DropGuard::new(
&raw mut (*slot).#ident
)
};
res.extend(quote! {
#(#cfgs)*
// Create the drop guard.
//
// SAFETY:
// - `&raw mut (*slot).#ident` is valid.
// - `make_field_check` checks that `&raw mut (*slot).#ident` is properly aligned.
// - `(*slot).#ident` has been initialized above.
// - We only need the ownership to the pointee back when initialization has
// succeeded, where we `forget` the guard.
let mut #guard = unsafe {
::pin_init::__internal::DropGuard::new(
&raw mut (*slot).#ident
)
};
#(#cfgs)*
#[allow(unused_variables)]
let #ident = #accessor;
});
guards.push(guard);
guard_attrs.push(cfgs);
}
#(#cfgs)*
#[allow(unused_variables)]
let #ident = #accessor;
});
guards.push(guard);
guard_attrs.push(cfgs);
}
quote! {
#res