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Add backcompat hack to support

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```rust
fn foo() -> impl MyTrait {
    panic!();
    MyStruct
}

struct MyStruct;
trait MyTrait {}

impl MyTrait for MyStruct {}
```
This commit is contained in:
Oli Scherer 2022-01-26 15:49:43 +00:00
parent edaf9625fb
commit 64c5b9a3d6
3 changed files with 28 additions and 16 deletions
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11
compiler/rustc_middle/src/ty/context.rs
View File

@ -30,6 +30,7 @@ use rustc_data_structures::sharded::{IntoPointer, ShardedHashMap};
use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
use rustc_data_structures::steal::Steal;
use rustc_data_structures::sync::{self, Lock, Lrc, WorkerLocal};
use rustc_data_structures::vec_map::VecMap;
use rustc_errors::ErrorReported;
use rustc_hir as hir;
use rustc_hir::def::{DefKind, Res};
@ -464,9 +465,13 @@ pub struct TypeckResults<'tcx> {
/// this field will be set to `Some(ErrorReported)`.
pub tainted_by_errors: Option<ErrorReported>,
/// All the opaque types that are restricted to concrete types
/// by this function.
pub concrete_opaque_types: FxHashSet<DefId>,
/// All the opaque types that have hidden types set
/// by this function. For return-position-impl-trait we also store the
/// type here, so that mir-borrowck can figure out hidden types,
/// even if they are only set in dead code (which doesn't show up in MIR).
/// For type-alias-impl-trait, this map is only used to prevent query cycles,
/// so the hidden types are all `None`.
pub concrete_opaque_types: VecMap<DefId, Option<Ty<'tcx>>>,
/// Tracks the minimum captures required for a closure;
/// see `MinCaptureInformationMap` for more details.

10
compiler/rustc_typeck/src/check/writeback.rs
View File

@ -499,8 +499,14 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
fn visit_opaque_types(&mut self) {
let opaque_types =
self.fcx.infcx.inner.borrow_mut().opaque_type_storage.take_opaque_types();
for (opaque_type_key, _) in opaque_types {
self.typeck_results.concrete_opaque_types.insert(opaque_type_key.def_id);
for (opaque_type_key, decl) in opaque_types {
let hidden_type = match decl.origin {
hir::OpaqueTyOrigin::FnReturn(_) | hir::OpaqueTyOrigin::AsyncFn(_) => {
Some(self.resolve(decl.hidden_type.ty, &decl.hidden_type.span))
}
hir::OpaqueTyOrigin::TyAlias => None,
};
self.typeck_results.concrete_opaque_types.insert(opaque_type_key.def_id, hidden_type);
}
}

23
compiler/rustc_typeck/src/collect/type_of.rs
View File

@ -389,21 +389,22 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
.get_value_matching(|(key, _)| key.def_id == def_id.to_def_id())
.copied()
.unwrap_or_else(|| {
if let Some(ErrorReported) =
tcx.typeck(owner).tainted_by_errors
{
let table = tcx.typeck(owner);
if let Some(ErrorReported) = table.tainted_by_errors {
// Some error in the
// owner fn prevented us from populating
// the `concrete_opaque_types` table.
tcx.ty_error()
} else {
// We failed to resolve the opaque type or it
// resolves to itself. We interpret this as the
// no values of the hidden type ever being constructed,
// so we can just make the hidden type be `!`.
// For backwards compatibility reasons, we fall back to
// `()` until we the diverging default is changed.
tcx.mk_diverging_default()
table.concrete_opaque_types.get(&def_id.to_def_id()).copied().unwrap_or_else(|| {
// We failed to resolve the opaque type or it
// resolves to itself. We interpret this as the
// no values of the hidden type ever being constructed,
// so we can just make the hidden type be `!`.
// For backwards compatibility reasons, we fall back to
// `()` until we the diverging default is changed.
Some(tcx.mk_diverging_default())
}).expect("RPIT always have a hidden type from typeck")
}
});
debug!("concrete_ty = {:?}", concrete_ty);
@ -597,7 +598,7 @@ fn find_opaque_ty_constraints(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Ty<'_> {
}
// Calling `mir_borrowck` can lead to cycle errors through
// const-checking, avoid calling it if we don't have to.
if !self.tcx.typeck(def_id).concrete_opaque_types.contains(&self.def_id) {
if self.tcx.typeck(def_id).concrete_opaque_types.get(&self.def_id).is_none() {
debug!("no constraints in typeck results");
return;
}