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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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33
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 collected_lifetimes = Vec::new();
let mut new_remapping = FxHashMap::default(); let mut new_remapping = FxHashMap::default();
self.with_hir_id_owner(opaque_ty_node_id, |lctx| { // If this came from a TAIT (as opposed to a function that returns an RPIT), we only want
if origin != hir::OpaqueTyOrigin::TyAlias { // to capture the lifetimes that appear in the bounds. So visit the bounds to find out
// When lowering `fn foo<'a>() -> impl Debug + 'a`, the `lifetime_collector` finds // exactly which ones those are.
// the set of lifetimes that appear in the bounds (in this case, 'a) and returns let lifetimes_to_remap = if origin == hir::OpaqueTyOrigin::TyAlias {
// that set in the variable lifetimes_in_bounds. // in a TAIT like `type Foo<'a> = impl Foo<'a>`, we don't keep all the lifetime parameters
let lifetimes_in_bounds = Vec::new()
lifetime_collector::lifetimes_in_bounds(&lctx.resolver, bounds); } else {
debug!(?lifetimes_in_bounds); // 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);
// For each captured lifetime (e.g., 'a), we create a new lifetime parameter that self.with_hir_id_owner(opaque_ty_node_id, |lctx| {
// is a generic defined on the TAIT, so we have type Foo<'a1> = ... and we // If this opaque type is only capturing a subset of the lifetimes (those that appear
// establish a mapping from the original parameter 'a to the new parameter 'a1. // 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( collected_lifetimes = lctx.create_lifetime_defs(
opaque_ty_def_id, opaque_ty_def_id,
&lifetimes_in_bounds, &lifetimes_to_remap,
&mut new_remapping, &mut new_remapping,
); );
};
debug!(?new_remapping);
debug!(?collected_lifetimes); debug!(?collected_lifetimes);
debug!(?new_remapping);
// Install the remapping from old to new (if any):
lctx.with_remapping(new_remapping, |lctx| { lctx.with_remapping(new_remapping, |lctx| {
// Then when we lower the param bounds, references to 'a are remapped to 'a1, so we // 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. // get back Debug + 'a1, which is suitable for use on the TAIT.