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Merged
nbdd0121 merged 2 commits into from
May 11, 2026
+113 −106
Merged

internal: pin_data: add struct to record field info #152

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13111ef
internal: pin_data: use closure for `handle_field`
nbdd0121 May 11, 2026
ef572c1
internal: pin_data: add struct to record field info
mqqz Apr 30, 2026
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191 changes: 99 additions & 92 deletions internal/src/pin_data.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,11 @@ impl Parse for Args {
}
}

struct FieldInfo<'a> {
field: &'a Field,
pinned: bool,
}

pub(crate) fn pin_data(
args: Args,
input: Item,
Expand Down Expand Up @@ -73,24 +78,30 @@ pub(crate) fn pin_data(
replacer.visit_generics_mut(&mut struct_.generics);
replacer.visit_fields_mut(&mut struct_.fields);

let fields: Vec<(bool, &Field)> = struct_
let fields: Vec<FieldInfo<'_>> = struct_
.fields
.iter_mut()
.map(|field| {
let len = field.attrs.len();
field.attrs.retain(|a| !a.path().is_ident("pin"));
(len != field.attrs.len(), &*field)
let pinned = len != field.attrs.len();

FieldInfo {
field: &*field,
pinned,
}
})
.collect();

for (pinned, field) in &fields {
if !pinned && is_phantom_pinned(&field.ty) {
for field in &fields {
let ident = field.field.ident.as_ref().unwrap();

if !field.pinned && is_phantom_pinned(&field.field.ty) {
dcx.warn(
field,
field.field,
format!(
"The field `{}` of type `PhantomPinned` only has an effect \
"The field `{ident}` of type `PhantomPinned` only has an effect \
if it has the `#[pin]` attribute",
field.ident.as_ref().unwrap(),
),
);
}
Expand Down Expand Up @@ -143,7 +154,7 @@ fn is_phantom_pinned(ty: &Type) -> bool {
fn generate_unpin_impl(
ident: &Ident,
generics: &Generics,
fields: &[(bool, &Field)],
fields: &[FieldInfo<'_>],
) -> TokenStream {
let (_, ty_generics, _) = generics.split_for_impl();
let mut generics_with_pin_lt = generics.clone();
Expand All @@ -160,7 +171,7 @@ fn generate_unpin_impl(
else {
unreachable!()
};
let pinned_fields = fields.iter().filter_map(|(b, f)| b.then_some(f));
let pinned_fields = fields.iter().filter(|f| f.pinned).map(|f| f.field);
quote! {
// This struct will be used for the unpin analysis. It is needed, because only structurally
// pinned fields are relevant whether the struct should implement `Unpin`.
Expand Down Expand Up @@ -238,7 +249,7 @@ fn generate_projections(
vis: &Visibility,
ident: &Ident,
generics: &Generics,
fields: &[(bool, &Field)],
fields: &[FieldInfo<'_>],
) -> TokenStream {
let (impl_generics, ty_generics, _) = generics.split_for_impl();
let mut generics_with_pin_lt = generics.clone();
Expand All @@ -249,21 +260,21 @@ fn generate_projections(

let (fields_decl, fields_proj): (Vec<_>, Vec<_>) = fields
.iter()
.map(|(pinned, field)| {
.map(|field| {
let Field {
vis,
ident,
ty,
attrs,
..
} = field;
} = &field.field;

let mut no_doc_attrs = attrs.clone();
no_doc_attrs.retain(|a| !a.path().is_ident("doc"));
let ident = ident
.as_ref()
.expect("only structs with named fields are supported");
if *pinned {
if field.pinned {
(
quote!(
#(#attrs)*
Expand Down Expand Up @@ -291,12 +302,12 @@ fn generate_projections(
.collect();
let structurally_pinned_fields_docs = fields
.iter()
.filter_map(|(pinned, field)| pinned.then_some(field))
.map(|Field { ident, .. }| format!(" - `{}`", ident.as_ref().unwrap()));
.filter(|f| f.pinned)
.map(|f| format!(" - `{}`", f.field.ident.as_ref().unwrap()));
let not_structurally_pinned_fields_docs = fields
.iter()
.filter_map(|(pinned, field)| (!pinned).then_some(field))
.map(|Field { ident, .. }| format!(" - `{}`", ident.as_ref().unwrap()));
.filter(|f| !f.pinned)
.map(|f| format!(" - `{}`", f.field.ident.as_ref().unwrap()));
let docs = format!(" Pin-projections of [`{ident}`]");
quote! {
#[doc = #docs]
Expand Down Expand Up @@ -336,9 +347,9 @@ fn generate_projections(

fn generate_the_pin_data(
vis: &Visibility,
ident: &Ident,
struct_name: &Ident,
generics: &Generics,
fields: &[(bool, &Field)],
fields: &[FieldInfo<'_>],
) -> TokenStream {
let (impl_generics, ty_generics, whr) = generics.split_for_impl();

Expand All @@ -347,78 +358,74 @@ fn generate_the_pin_data(
// not structurally pinned, then it can be initialized via `Init`.
//
// The functions are `unsafe` to prevent accidentally calling them.
fn handle_field(
Field {
vis,
ident,
ty,
attrs,
..
}: &Field,
struct_ident: &Ident,
pinned: bool,
) -> TokenStream {
let ident = ident
.as_ref()
.expect("only structs with named fields are supported");
let project_ident = format_ident!("__project_{ident}");
let (init_ty, init_fn, project_ty, project_body, pin_safety) = if pinned {
(
quote!(PinInit),
quote!(__pinned_init),
quote!(::core::pin::Pin<&'__slot mut #ty>),
// SAFETY: this field is structurally pinned.
quote!(unsafe { ::core::pin::Pin::new_unchecked(slot) }),
quote!(
/// - `slot` will not move until it is dropped, i.e. it will be pinned.
),
)
} else {
(
quote!(Init),
quote!(__init),
quote!(&'__slot mut #ty),
quote!(slot),
quote!(),
)
};
let slot_safety = format!(
" `slot` points at the field `{ident}` inside of `{struct_ident}`, which is pinned.",
);
quote! {
/// # Safety
///
/// - `slot` is a valid pointer to uninitialized memory.
/// - the caller does not touch `slot` when `Err` is returned, they are only permitted
/// to deallocate.
#pin_safety
#(#attrs)*
#vis unsafe fn #ident<E>(
self,
slot: *mut #ty,
init: impl ::pin_init::#init_ty<#ty, E>,
) -> ::core::result::Result<(), E> {
// SAFETY: this function has the same safety requirements as the __init function
// called below.
unsafe { ::pin_init::#init_ty::#init_fn(init, slot) }
}

/// # Safety
///
#[doc = #slot_safety]
#(#attrs)*
#vis unsafe fn #project_ident<'__slot>(
self,
slot: &'__slot mut #ty,
) -> #project_ty {
#project_body
}
}
}

let field_accessors = fields
.iter()
.map(|(pinned, field)| handle_field(field, ident, *pinned))
.map(|f| {
let Field {
vis,
ident,
ty,
attrs,
..
} = f.field;

let field_name = ident
.as_ref()
.expect("only structs with named fields are supported");
let project_ident = format_ident!("__project_{field_name}");
let (init_ty, init_fn, project_ty, project_body, pin_safety) = if f.pinned {
(
quote!(PinInit),
quote!(__pinned_init),
quote!(::core::pin::Pin<&'__slot mut #ty>),
// SAFETY: this field is structurally pinned.
quote!(unsafe { ::core::pin::Pin::new_unchecked(slot) }),
quote!(
/// - `slot` will not move until it is dropped, i.e. it will be pinned.
),
)
} else {
(
quote!(Init),
quote!(__init),
quote!(&'__slot mut #ty),
quote!(slot),
quote!(),
)
};
let slot_safety = format!(
" `slot` points at the field `{field_name}` inside of `{struct_name}`, which is pinned.",
);
quote! {
/// # Safety
///
/// - `slot` is a valid pointer to uninitialized memory.
/// - the caller does not touch `slot` when `Err` is returned, they are only
/// permitted to deallocate.
#pin_safety
#(#attrs)*
#vis unsafe fn #field_name<E>(
self,
slot: *mut #ty,
init: impl ::pin_init::#init_ty<#ty, E>,
) -> ::core::result::Result<(), E> {
// SAFETY: this function has the same safety requirements as the __init function
// called below.
unsafe { ::pin_init::#init_ty::#init_fn(init, slot) }
}

/// # Safety
///
#[doc = #slot_safety]
#(#attrs)*
#vis unsafe fn #project_ident<'__slot>(
self,
slot: &'__slot mut #ty,
) -> #project_ty {
#project_body
}
}
})
.collect::<TokenStream>();
quote! {
// We declare this struct which will host all of the projection function for our type. It
Expand All @@ -428,7 +435,7 @@ fn generate_the_pin_data(
#whr
{
__phantom: ::core::marker::PhantomData<
fn(#ident #ty_generics) -> #ident #ty_generics
fn(#struct_name #ty_generics) -> #struct_name #ty_generics
>,
}

Expand All @@ -452,7 +459,7 @@ fn generate_the_pin_data(

// SAFETY: We have added the correct projection functions above to `__ThePinData` and
// we also use the least restrictive generics possible.
unsafe impl #impl_generics ::pin_init::__internal::HasPinData for #ident #ty_generics
unsafe impl #impl_generics ::pin_init::__internal::HasPinData for #struct_name #ty_generics
#whr
{
type PinData = __ThePinData #ty_generics;
Expand All @@ -466,7 +473,7 @@ fn generate_the_pin_data(
unsafe impl #impl_generics ::pin_init::__internal::PinData for __ThePinData #ty_generics
#whr
{
type Datee = #ident #ty_generics;
type Datee = #struct_name #ty_generics;
}
}
}
Expand Down
12 changes: 6 additions & 6 deletions tests/ui/expand/many_generics.expanded.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -87,8 +87,8 @@ const _: () = {
/// # Safety
///
/// - `slot` is a valid pointer to uninitialized memory.
/// - the caller does not touch `slot` when `Err` is returned, they are only permitted
/// to deallocate.
/// - the caller does not touch `slot` when `Err` is returned, they are only
/// permitted to deallocate.
unsafe fn array<E>(
self,
slot: *mut [u8; 1024 * 1024],
Expand All @@ -108,8 +108,8 @@ const _: () = {
/// # Safety
///
/// - `slot` is a valid pointer to uninitialized memory.
/// - the caller does not touch `slot` when `Err` is returned, they are only permitted
/// to deallocate.
/// - the caller does not touch `slot` when `Err` is returned, they are only
/// permitted to deallocate.
unsafe fn r<E>(
self,
slot: *mut &'b mut [&'a mut T; SIZE],
Expand All @@ -129,8 +129,8 @@ const _: () = {
/// # Safety
///
/// - `slot` is a valid pointer to uninitialized memory.
/// - the caller does not touch `slot` when `Err` is returned, they are only permitted
/// to deallocate.
/// - the caller does not touch `slot` when `Err` is returned, they are only
/// permitted to deallocate.
/// - `slot` will not move until it is dropped, i.e. it will be pinned.
unsafe fn _pin<E>(
self,
Expand Down
8 changes: 4 additions & 4 deletions tests/ui/expand/pin-data.expanded.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -49,8 +49,8 @@ const _: () = {
/// # Safety
///
/// - `slot` is a valid pointer to uninitialized memory.
/// - the caller does not touch `slot` when `Err` is returned, they are only permitted
/// to deallocate.
/// - the caller does not touch `slot` when `Err` is returned, they are only
/// permitted to deallocate.
unsafe fn array<E>(
self,
slot: *mut [u8; 1024 * 1024],
Expand All @@ -70,8 +70,8 @@ const _: () = {
/// # Safety
///
/// - `slot` is a valid pointer to uninitialized memory.
/// - the caller does not touch `slot` when `Err` is returned, they are only permitted
/// to deallocate.
/// - the caller does not touch `slot` when `Err` is returned, they are only
/// permitted to deallocate.
/// - `slot` will not move until it is dropped, i.e. it will be pinned.
unsafe fn _pin<E>(
self,
Expand Down
8 changes: 4 additions & 4 deletions tests/ui/expand/pinned_drop.expanded.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -49,8 +49,8 @@ const _: () = {
/// # Safety
///
/// - `slot` is a valid pointer to uninitialized memory.
/// - the caller does not touch `slot` when `Err` is returned, they are only permitted
/// to deallocate.
/// - the caller does not touch `slot` when `Err` is returned, they are only
/// permitted to deallocate.
unsafe fn array<E>(
self,
slot: *mut [u8; 1024 * 1024],
Expand All @@ -70,8 +70,8 @@ const _: () = {
/// # Safety
///
/// - `slot` is a valid pointer to uninitialized memory.
/// - the caller does not touch `slot` when `Err` is returned, they are only permitted
/// to deallocate.
/// - the caller does not touch `slot` when `Err` is returned, they are only
/// permitted to deallocate.
/// - `slot` will not move until it is dropped, i.e. it will be pinned.
unsafe fn _pin<E>(
self,
Expand Down
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