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Move lifetimes_in_bounds call to outside with_hir_id_owner block in lower_opaque_impl_trait

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Santiago Pastorino 2022-08-03 23:16:03 -03:00
parent 76b518fc83
commit 4b9b5838ac
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1 changed files with 23 additions and 18 deletions
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41
compiler/rustc_ast_lowering/src/lib.rs
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@ -1400,27 +1400,32 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
let mut collected_lifetimes = Vec::new();
let mut new_remapping = FxHashMap::default();
// If this came from a TAIT (as opposed to a function that returns an RPIT), we only want
// to capture the lifetimes that appear in the bounds. So visit the bounds to find out
// exactly which ones those are.
let lifetimes_to_remap = if origin == hir::OpaqueTyOrigin::TyAlias {
// in a TAIT like `type Foo<'a> = impl Foo<'a>`, we don't keep all the lifetime parameters
Vec::new()
} else {
// in fn return position, like the `fn test<'a>() -> impl Debug + 'a` example,
// we only keep the lifetimes that appear in the `impl Debug` itself:
lifetime_collector::lifetimes_in_bounds(&self.resolver, bounds)
};
debug!(?lifetimes_to_remap);
self.with_hir_id_owner(opaque_ty_node_id, |lctx| {
if origin != hir::OpaqueTyOrigin::TyAlias {
// When lowering `fn foo<'a>() -> impl Debug + 'a`, the `lifetime_collector` finds
// the set of lifetimes that appear in the bounds (in this case, 'a) and returns
// that set in the variable lifetimes_in_bounds.
let lifetimes_in_bounds =
lifetime_collector::lifetimes_in_bounds(&lctx.resolver, bounds);
debug!(?lifetimes_in_bounds);
// For each captured lifetime (e.g., 'a), we create a new lifetime parameter that
// is a generic defined on the TAIT, so we have type Foo<'a1> = ... and we
// establish a mapping from the original parameter 'a to the new parameter 'a1.
collected_lifetimes = lctx.create_lifetime_defs(
opaque_ty_def_id,
&lifetimes_in_bounds,
&mut new_remapping,
);
};
debug!(?new_remapping);
// If this opaque type is only capturing a subset of the lifetimes (those that appear
// in bounds), then create the new lifetime parameters required and create a mapping
// from the old `'a` (on the function) to the new `'a` (on the opaque type).
collected_lifetimes = lctx.create_lifetime_defs(
opaque_ty_def_id,
&lifetimes_to_remap,
&mut new_remapping,
);
debug!(?collected_lifetimes);
debug!(?new_remapping);
// Install the remapping from old to new (if any):
lctx.with_remapping(new_remapping, |lctx| {
// Then when we lower the param bounds, references to 'a are remapped to 'a1, so we
// get back Debug + 'a1, which is suitable for use on the TAIT.