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Auto merge of #103205 - spastorino:fix-rpits-lifetime-remapping, r=cj…
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…gillot

Do anonymous lifetimes remapping correctly for nested rpits

Closes #103141

r? `@cjgillot` `@nikomatsakis`

This fixes a stable to stable regression that in my opinion is `P-critical` so, we probably want to backport it all the way up to stable.
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bors committed Oct 20, 2022
2 parents cb94675 + 49ce8a2 commit ebdde35
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Showing 2 changed files with 46 additions and 20 deletions.
43 changes: 23 additions & 20 deletions compiler/rustc_ast_lowering/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -506,6 +506,17 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
start
}

/// Given the id of some node in the AST, finds the `LocalDefId` associated with it by the name
/// resolver (if any).
fn orig_opt_local_def_id(&self, node: NodeId) -> Option<LocalDefId> {
self.resolver.node_id_to_def_id.get(&node).map(|local_def_id| *local_def_id)
}

fn orig_local_def_id(&self, node: NodeId) -> LocalDefId {
self.orig_opt_local_def_id(node)
.unwrap_or_else(|| panic!("no entry for node id: `{:?}`", node))
}

/// Given the id of some node in the AST, finds the `LocalDefId` associated with it by the name
/// resolver (if any), after applying any remapping from `get_remapped_def_id`.
///
Expand All @@ -520,10 +531,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
/// we would create an opaque type `type FooReturn<'a1> = impl Debug + 'a1`.
/// When lowering the `Debug + 'a` bounds, we add a remapping to map `'a` to `'a1`.
fn opt_local_def_id(&self, node: NodeId) -> Option<LocalDefId> {
self.resolver
.node_id_to_def_id
.get(&node)
.map(|local_def_id| self.get_remapped_def_id(*local_def_id))
self.orig_opt_local_def_id(node).map(|local_def_id| self.get_remapped_def_id(local_def_id))
}

fn local_def_id(&self, node: NodeId) -> LocalDefId {
Expand All @@ -532,9 +540,9 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {

/// Get the previously recorded `to` local def id given the `from` local def id, obtained using
/// `generics_def_id_map` field.
fn get_remapped_def_id(&self, mut local_def_id: LocalDefId) -> LocalDefId {
fn get_remapped_def_id(&self, local_def_id: LocalDefId) -> LocalDefId {
// `generics_def_id_map` is a stack of mappings. As we go deeper in impl traits nesting we
// push new mappings so we need to try first the latest mappings, hence `iter().rev()`.
// push new mappings, so we first need to get the latest (innermost) mappings, hence `iter().rev()`.
//
// Consider:
//
Expand All @@ -544,18 +552,13 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
//
// `[[fn#'b -> impl_trait#'b], [fn#'b -> impl_sized#'b]]`
//
// for the opaque type generated on `impl Sized + 'b`, We want the result to be:
// impl_sized#'b, so iterating forward is the wrong thing to do.
for map in self.generics_def_id_map.iter().rev() {
if let Some(r) = map.get(&local_def_id) {
debug!("def_id_remapper: remapping from `{local_def_id:?}` to `{r:?}`");
local_def_id = *r;
} else {
debug!("def_id_remapper: no remapping for `{local_def_id:?}` found in map");
}
}

local_def_id
// for the opaque type generated on `impl Sized + 'b`, we want the result to be: impl_sized#'b.
// So, if we were trying to find first from the start (outermost) would give the wrong result, impl_trait#'b.
self.generics_def_id_map
.iter()
.rev()
.find_map(|map| map.get(&local_def_id).map(|local_def_id| *local_def_id))
.unwrap_or(local_def_id)
}

/// Freshen the `LoweringContext` and ready it to lower a nested item.
Expand Down Expand Up @@ -1633,7 +1636,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {

LifetimeRes::Fresh { param, binder: _ } => {
debug_assert_eq!(lifetime.ident.name, kw::UnderscoreLifetime);
if let Some(old_def_id) = self.opt_local_def_id(param) && remapping.get(&old_def_id).is_none() {
if let Some(old_def_id) = self.orig_opt_local_def_id(param) && remapping.get(&old_def_id).is_none() {
let node_id = self.next_node_id();

let new_def_id = self.create_def(
Expand Down Expand Up @@ -1878,7 +1881,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
let extra_lifetime_params = self.resolver.take_extra_lifetime_params(opaque_ty_node_id);
debug!(?extra_lifetime_params);
for (ident, outer_node_id, outer_res) in extra_lifetime_params {
let outer_def_id = self.local_def_id(outer_node_id);
let outer_def_id = self.orig_local_def_id(outer_node_id);
let inner_node_id = self.next_node_id();

// Add a definition for the in scope lifetime def.
Expand Down
23 changes: 23 additions & 0 deletions src/test/ui/impl-trait/nested-rpit-with-anonymous-lifetimes.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,23 @@
// check-pass

pub struct VecNumber<'s> {
pub vec_number: Vec<Number<'s>>,
pub auxiliary_object: &'s Vec<usize>,
}

pub struct Number<'s> {
pub number: &'s usize,
}

impl<'s> VecNumber<'s> {
pub fn vec_number_iterable_per_item_in_auxiliary_object(
&self,
) -> impl Iterator<Item = (&'s usize, impl Iterator<Item = &Number<'s>>)> {
self.auxiliary_object.iter().map(move |n| {
let iter_number = self.vec_number.iter();
(n, iter_number)
})
}
}

fn main() {}

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