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Rollup merge of #120143 - compiler-errors:consolidate-instance-resolve-for-coroutines, r=oli-obk

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Consolidate logic around resolving built-in coroutine trait impls

Deduplicates a lot of code. Requires defining a new lang item for `Coroutine::resume` for consistency, but it seems not harmful at worst, and potentially later useful at best.

r? oli-obk
This commit is contained in:
Matthias Krüger 2024-01-22 22:12:08 +01:00 • committed by GitHub
commit 221115cbd6
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5 changed files with 56 additions and 58 deletions
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50
compiler/rustc_middle/src/ty/instance.rs
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@ -3,6 +3,7 @@ use crate::ty::print::{FmtPrinter, Printer};
use crate::ty::{self, Ty, TyCtxt, TypeFoldable, TypeSuperFoldable};
use crate::ty::{EarlyBinder, GenericArgs, GenericArgsRef, TypeVisitableExt};
use rustc_errors::ErrorGuaranteed;
use rustc_hir as hir;
use rustc_hir::def::Namespace;
use rustc_hir::def_id::{CrateNum, DefId};
use rustc_hir::lang_items::LangItem;
@ -11,6 +12,7 @@ use rustc_macros::HashStable;
use rustc_middle::ty::normalize_erasing_regions::NormalizationError;
use rustc_span::Symbol;
use std::assert_matches::assert_matches;
use std::fmt;
/// A monomorphized `InstanceDef`.
@ -572,6 +574,54 @@ impl<'tcx> Instance<'tcx> {
Some(Instance { def, args })
}
pub fn try_resolve_item_for_coroutine(
tcx: TyCtxt<'tcx>,
trait_item_id: DefId,
trait_id: DefId,
rcvr_args: ty::GenericArgsRef<'tcx>,
) -> Option<Instance<'tcx>> {
let ty::Coroutine(coroutine_def_id, args) = *rcvr_args.type_at(0).kind() else {
return None;
};
let coroutine_kind = tcx.coroutine_kind(coroutine_def_id).unwrap();
let lang_items = tcx.lang_items();
let coroutine_callable_item = if Some(trait_id) == lang_items.future_trait() {
assert_matches!(
coroutine_kind,
hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Async, _)
);
hir::LangItem::FuturePoll
} else if Some(trait_id) == lang_items.iterator_trait() {
assert_matches!(
coroutine_kind,
hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Gen, _)
);
hir::LangItem::IteratorNext
} else if Some(trait_id) == lang_items.async_iterator_trait() {
assert_matches!(
coroutine_kind,
hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::AsyncGen, _)
);
hir::LangItem::AsyncIteratorPollNext
} else if Some(trait_id) == lang_items.coroutine_trait() {
assert_matches!(coroutine_kind, hir::CoroutineKind::Coroutine(_));
hir::LangItem::CoroutineResume
} else {
return None;
};
if tcx.lang_items().get(coroutine_callable_item) == Some(trait_item_id) {
Some(Instance { def: ty::InstanceDef::Item(coroutine_def_id), args: args })
} else {
// All other methods should be defaulted methods of the built-in trait.
// This is important for `Iterator`'s combinators, but also useful for
// adding future default methods to `Future`, for instance.
debug_assert!(tcx.defaultness(trait_item_id).has_value());
Some(Instance::new(trait_item_id, rcvr_args))
}
}
/// Depending on the kind of `InstanceDef`, the MIR body associated with an
/// instance is expressed in terms of the generic parameters of `self.def_id()`, and in other
/// cases the MIR body is expressed in terms of the types found in the substitution array.