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derive(SmartPointer): rewrite bounds in where and generic bounds #127681
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Original file line number | Diff line number | Diff line change |
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@@ -1,14 +1,18 @@ | ||
use std::mem::swap; | ||
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use ast::ptr::P; | ||
use ast::HasAttrs; | ||
use rustc_ast::mut_visit::MutVisitor; | ||
use rustc_ast::visit::BoundKind; | ||
use rustc_ast::{ | ||
self as ast, GenericArg, GenericBound, GenericParamKind, ItemKind, MetaItem, | ||
TraitBoundModifiers, VariantData, | ||
TraitBoundModifiers, VariantData, WherePredicate, | ||
}; | ||
use rustc_attr as attr; | ||
use rustc_data_structures::flat_map_in_place::FlatMapInPlace; | ||
use rustc_expand::base::{Annotatable, ExtCtxt}; | ||
use rustc_span::symbol::{sym, Ident}; | ||
use rustc_span::Span; | ||
use rustc_span::{Span, Symbol}; | ||
use smallvec::{smallvec, SmallVec}; | ||
use thin_vec::{thin_vec, ThinVec}; | ||
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@@ -141,33 +145,239 @@ pub fn expand_deriving_smart_ptr( | |
alt_self_params[pointee_param_idx] = GenericArg::Type(s_ty.clone()); | ||
let alt_self_type = cx.ty_path(cx.path_all(span, false, vec![name_ident], alt_self_params)); | ||
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// # Add `Unsize<__S>` bound to `#[pointee]` at the generic parameter location | ||
// | ||
// Find the `#[pointee]` parameter and add an `Unsize<__S>` bound to it. | ||
let mut impl_generics = generics.clone(); | ||
let pointee_ty_ident = generics.params[pointee_param_idx].ident; | ||
let mut self_bounds; | ||
{ | ||
let p = &mut impl_generics.params[pointee_param_idx]; | ||
let pointee = &mut impl_generics.params[pointee_param_idx]; | ||
self_bounds = pointee.bounds.clone(); | ||
let arg = GenericArg::Type(s_ty.clone()); | ||
let unsize = cx.path_all(span, true, path!(span, core::marker::Unsize), vec![arg]); | ||
p.bounds.push(cx.trait_bound(unsize, false)); | ||
pointee.bounds.push(cx.trait_bound(unsize, false)); | ||
let mut attrs = thin_vec![]; | ||
swap(&mut p.attrs, &mut attrs); | ||
p.attrs = attrs.into_iter().filter(|attr| !attr.has_name(sym::pointee)).collect(); | ||
swap(&mut pointee.attrs, &mut attrs); | ||
// Drop `#[pointee]` attribute since it should not be recognized outside `derive(SmartPointer)` | ||
pointee.attrs = attrs.into_iter().filter(|attr| !attr.has_name(sym::pointee)).collect(); | ||
} | ||
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// Add the `__S: ?Sized` extra parameter to the impl block. | ||
// # Rewrite generic parameter bounds | ||
// For each bound `U: ..` in `struct<U: ..>`, make a new bound with `__S` in place of `#[pointee]` | ||
// Example: | ||
// ``` | ||
// struct< | ||
// U: Trait<T>, | ||
// #[pointee] T: Trait<T>, | ||
// V: Trait<T>> ... | ||
// ``` | ||
// ... generates this `impl` generic parameters | ||
// ``` | ||
// impl< | ||
// U: Trait<T> + Trait<__S>, | ||
// T: Trait<T> + Unsize<__S>, // (**) | ||
// __S: Trait<__S> + ?Sized, // (*) | ||
// V: Trait<T> + Trait<__S>> ... | ||
// ``` | ||
// The new bound marked with (*) has to be done separately. | ||
// See next section | ||
for (idx, (params, orig_params)) in | ||
impl_generics.params.iter_mut().zip(&generics.params).enumerate() | ||
{ | ||
// Default type parameters are rejected for `impl` block. | ||
// We should drop them now. | ||
match &mut params.kind { | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Move the comment from above into here, and split it up so each part ( There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Applied |
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ast::GenericParamKind::Const { default, .. } => *default = None, | ||
ast::GenericParamKind::Type { default } => *default = None, | ||
ast::GenericParamKind::Lifetime => {} | ||
} | ||
// We CANNOT rewrite `#[pointee]` type parameter bounds. | ||
// This has been set in stone. (**) | ||
// So we skip over it. | ||
// Otherwise, we push extra bounds involving `__S`. | ||
if idx != pointee_param_idx { | ||
for bound in &orig_params.bounds { | ||
let mut bound = bound.clone(); | ||
let mut substitution = TypeSubstitution { | ||
from_name: pointee_ty_ident.name, | ||
to_ty: &s_ty, | ||
rewritten: false, | ||
}; | ||
substitution.visit_param_bound(&mut bound, BoundKind::Bound); | ||
if substitution.rewritten { | ||
// We found use of `#[pointee]` somewhere, | ||
// so we make a new bound using `__S` in place of `#[pointee]` | ||
params.bounds.push(bound); | ||
} | ||
} | ||
} | ||
} | ||
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// # Insert `__S` type parameter | ||
// | ||
// We now insert `__S` with the missing bounds marked with (*) above. | ||
// We should also write the bounds from `#[pointee]` to `__S` as required by `Unsize<__S>`. | ||
let sized = cx.path_global(span, path!(span, core::marker::Sized)); | ||
let bound = GenericBound::Trait( | ||
cx.poly_trait_ref(span, sized), | ||
TraitBoundModifiers { | ||
polarity: ast::BoundPolarity::Maybe(span), | ||
constness: ast::BoundConstness::Never, | ||
asyncness: ast::BoundAsyncness::Normal, | ||
}, | ||
); | ||
let extra_param = cx.typaram(span, Ident::new(sym::__S, span), vec![bound], None); | ||
impl_generics.params.push(extra_param); | ||
// For some reason, we are not allowed to write `?Sized` bound twice like `__S: ?Sized + ?Sized`. | ||
if !contains_maybe_sized_bound(&self_bounds) | ||
&& !contains_maybe_sized_bound_on_pointee( | ||
&generics.where_clause.predicates, | ||
pointee_ty_ident.name, | ||
) | ||
{ | ||
self_bounds.push(GenericBound::Trait( | ||
cx.poly_trait_ref(span, sized), | ||
TraitBoundModifiers { | ||
polarity: ast::BoundPolarity::Maybe(span), | ||
constness: ast::BoundConstness::Never, | ||
asyncness: ast::BoundAsyncness::Normal, | ||
}, | ||
)); | ||
} | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. You never have to add a There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Applied. So this section is yanked, and assertion has added earlier to require this bound. |
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{ | ||
let mut substitution = | ||
TypeSubstitution { from_name: pointee_ty_ident.name, to_ty: &s_ty, rewritten: false }; | ||
for bound in &mut self_bounds { | ||
substitution.visit_param_bound(bound, BoundKind::Bound); | ||
} | ||
} | ||
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// # Rewrite `where` clauses | ||
// | ||
// Move on to `where` clauses. | ||
// Example: | ||
// ``` | ||
// struct MyPointer<#[pointee] T, ..> | ||
// where | ||
// U: Trait<V> + Trait<T>, | ||
// Companion<T>: Trait<T>, | ||
// T: Trait<T>, | ||
// { .. } | ||
// ``` | ||
// ... will have a impl prelude like so | ||
// ``` | ||
// impl<..> .. | ||
// where | ||
// U: Trait<V> + Trait<T>, | ||
// U: Trait<__S>, | ||
// Companion<T>: Trait<T>, | ||
// Companion<__S>: Trait<__S>, | ||
// T: Trait<T>, | ||
// __S: Trait<__S>, | ||
// ``` | ||
// | ||
// We should also write a few new `where` bounds from `#[pointee] T` to `__S` | ||
// as well as any bound that indirectly involves the `#[pointee] T` type. | ||
for bound in &generics.where_clause.predicates { | ||
if let ast::WherePredicate::BoundPredicate(bound) = bound { | ||
let mut substitution = TypeSubstitution { | ||
from_name: pointee_ty_ident.name, | ||
to_ty: &s_ty, | ||
rewritten: false, | ||
}; | ||
let mut predicate = ast::WherePredicate::BoundPredicate(ast::WhereBoundPredicate { | ||
span: bound.span, | ||
bound_generic_params: bound.bound_generic_params.clone(), | ||
bounded_ty: bound.bounded_ty.clone(), | ||
bounds: bound.bounds.clone(), | ||
}); | ||
substitution.visit_where_predicate(&mut predicate); | ||
if substitution.rewritten { | ||
impl_generics.where_clause.predicates.push(predicate); | ||
} | ||
} | ||
} | ||
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let extra_param = cx.typaram(span, Ident::new(sym::__S, span), self_bounds, None); | ||
impl_generics.params.insert(pointee_param_idx + 1, extra_param); | ||
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// Add the impl blocks for `DispatchFromDyn` and `CoerceUnsized`. | ||
let gen_args = vec![GenericArg::Type(alt_self_type.clone())]; | ||
add_impl_block(impl_generics.clone(), sym::DispatchFromDyn, gen_args.clone()); | ||
add_impl_block(impl_generics.clone(), sym::CoerceUnsized, gen_args.clone()); | ||
} | ||
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fn contains_maybe_sized_bound_on_pointee(predicates: &[WherePredicate], pointee: Symbol) -> bool { | ||
for bound in predicates { | ||
if let ast::WherePredicate::BoundPredicate(bound) = bound | ||
&& bound.bounded_ty.kind.is_simple_path().is_some_and(|name| name == pointee) | ||
{ | ||
for bound in &bound.bounds { | ||
if is_maybe_sized_bound(bound) { | ||
return true; | ||
} | ||
} | ||
} | ||
} | ||
false | ||
} | ||
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fn is_maybe_sized_bound(bound: &GenericBound) -> bool { | ||
if let GenericBound::Trait( | ||
trait_ref, | ||
TraitBoundModifiers { polarity: ast::BoundPolarity::Maybe(_), .. }, | ||
) = bound | ||
{ | ||
is_sized_marker(&trait_ref.trait_ref.path) | ||
} else { | ||
false | ||
} | ||
} | ||
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fn contains_maybe_sized_bound(bounds: &[GenericBound]) -> bool { | ||
bounds.iter().any(is_maybe_sized_bound) | ||
} | ||
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fn path_segment_is_exact_match(path_segments: &[ast::PathSegment], syms: &[Symbol]) -> bool { | ||
path_segments.iter().zip(syms).all(|(segment, &symbol)| segment.ident.name == symbol) | ||
} | ||
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fn is_sized_marker(path: &ast::Path) -> bool { | ||
const CORE_UNSIZE: [Symbol; 3] = [sym::core, sym::marker, sym::Sized]; | ||
const STD_UNSIZE: [Symbol; 3] = [sym::std, sym::marker, sym::Sized]; | ||
if path.segments.len() == 4 && path.is_global() { | ||
path_segment_is_exact_match(&path.segments[1..], &CORE_UNSIZE) | ||
|| path_segment_is_exact_match(&path.segments[1..], &STD_UNSIZE) | ||
} else if path.segments.len() == 3 { | ||
path_segment_is_exact_match(&path.segments, &CORE_UNSIZE) | ||
|| path_segment_is_exact_match(&path.segments, &STD_UNSIZE) | ||
} else { | ||
*path == sym::Sized | ||
} | ||
} | ||
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struct TypeSubstitution<'a> { | ||
from_name: Symbol, | ||
to_ty: &'a ast::Ty, | ||
rewritten: bool, | ||
} | ||
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impl<'a> ast::mut_visit::MutVisitor for TypeSubstitution<'a> { | ||
fn visit_ty(&mut self, ty: &mut P<ast::Ty>) { | ||
if let Some(name) = ty.kind.is_simple_path() | ||
&& name == self.from_name | ||
{ | ||
**ty = self.to_ty.clone(); | ||
self.rewritten = true; | ||
} else { | ||
ast::mut_visit::walk_ty(self, ty); | ||
} | ||
} | ||
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fn visit_where_predicate(&mut self, where_predicate: &mut ast::WherePredicate) { | ||
match where_predicate { | ||
rustc_ast::WherePredicate::BoundPredicate(bound) => { | ||
bound | ||
.bound_generic_params | ||
.flat_map_in_place(|param| self.flat_map_generic_param(param)); | ||
self.visit_ty(&mut bound.bounded_ty); | ||
for bound in &mut bound.bounds { | ||
self.visit_param_bound(bound, BoundKind::Bound) | ||
} | ||
} | ||
rustc_ast::WherePredicate::RegionPredicate(_) | ||
| rustc_ast::WherePredicate::EqPredicate(_) => {} | ||
} | ||
} | ||
} |
Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1,22 @@ | ||
//@ check-pass | ||
//@ compile-flags: -Zunpretty=expanded | ||
#![feature(derive_smart_pointer)] | ||
use std::marker::SmartPointer; | ||
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pub trait MyTrait<T: ?Sized> {} | ||
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#[derive(SmartPointer)] | ||
#[repr(transparent)] | ||
struct MyPointer<'a, #[pointee] T: ?Sized> { | ||
ptr: &'a T, | ||
} | ||
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#[derive(core::marker::SmartPointer)] | ||
#[repr(transparent)] | ||
pub struct MyPointer2<'a, Y, Z: MyTrait<T>, #[pointee] T: ?Sized + MyTrait<T>, X: MyTrait<T> = ()> | ||
where | ||
Y: MyTrait<T>, | ||
{ | ||
data: &'a mut T, | ||
x: core::marker::PhantomData<X>, | ||
} |
Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1,44 @@ | ||
#![feature(prelude_import)] | ||
#![no_std] | ||
//@ check-pass | ||
//@ compile-flags: -Zunpretty=expanded | ||
#![feature(derive_smart_pointer)] | ||
#[prelude_import] | ||
use ::std::prelude::rust_2015::*; | ||
#[macro_use] | ||
extern crate std; | ||
use std::marker::SmartPointer; | ||
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pub trait MyTrait<T: ?Sized> {} | ||
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#[repr(transparent)] | ||
struct MyPointer<'a, #[pointee] T: ?Sized> { | ||
ptr: &'a T, | ||
} | ||
#[automatically_derived] | ||
impl<'a, T: ?Sized + ::core::marker::Unsize<__S>, __S: ?Sized> | ||
::core::ops::DispatchFromDyn<MyPointer<'a, __S>> for MyPointer<'a, T> { | ||
} | ||
#[automatically_derived] | ||
impl<'a, T: ?Sized + ::core::marker::Unsize<__S>, __S: ?Sized> | ||
::core::ops::CoerceUnsized<MyPointer<'a, __S>> for MyPointer<'a, T> { | ||
} | ||
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#[repr(transparent)] | ||
pub struct MyPointer2<'a, Y, Z: MyTrait<T>, #[pointee] T: ?Sized + MyTrait<T>, | ||
X: MyTrait<T> = ()> where Y: MyTrait<T> { | ||
data: &'a mut T, | ||
x: core::marker::PhantomData<X>, | ||
} | ||
#[automatically_derived] | ||
impl<'a, Y, Z: MyTrait<T> + MyTrait<__S>, T: ?Sized + MyTrait<T> + | ||
::core::marker::Unsize<__S>, __S: ?Sized + MyTrait<__S>, X: MyTrait<T> + | ||
MyTrait<__S>> ::core::ops::DispatchFromDyn<MyPointer2<'a, Y, Z, __S, X>> | ||
for MyPointer2<'a, Y, Z, T, X> where Y: MyTrait<T>, Y: MyTrait<__S> { | ||
} | ||
#[automatically_derived] | ||
impl<'a, Y, Z: MyTrait<T> + MyTrait<__S>, T: ?Sized + MyTrait<T> + | ||
::core::marker::Unsize<__S>, __S: ?Sized + MyTrait<__S>, X: MyTrait<T> + | ||
MyTrait<__S>> ::core::ops::CoerceUnsized<MyPointer2<'a, Y, Z, __S, X>> for | ||
MyPointer2<'a, Y, Z, T, X> where Y: MyTrait<T>, Y: MyTrait<__S> { | ||
} |
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Can be done as a follow-up, but can't this be rewritten as
.retain
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Yes 👍
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If you're already making changes, please also change this.
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I have not forgotten.
Applied in appendix commit.