From 34de78fd8131ac8149caab086c9696899d8d2bed Mon Sep 17 00:00:00 2001
From: Oli Scherer <github35764891676564198441@oli-obk.de>
Date: Tue, 10 Aug 2021 11:45:32 +0000
Subject: [PATCH] Generate inference vars and obligations for projections in
opaque types instead of trying to normalize them.
---
.../rustc_trait_selection/src/opaque_types.rs | 41 +++++++++++--------
src/test/ui/impl-trait/issue-72911.rs | 1 +
src/test/ui/impl-trait/issue-72911.stderr | 14 +++++--
3 files changed, 35 insertions(+), 21 deletions(-)
diff --git a/compiler/rustc_trait_selection/src/opaque_types.rs b/compiler/rustc_trait_selection/src/opaque_types.rs
index c3c565cc08f..04ce0c56c2a 100644
--- a/compiler/rustc_trait_selection/src/opaque_types.rs
+++ b/compiler/rustc_trait_selection/src/opaque_types.rs
@@ -1,4 +1,3 @@
-use crate::infer::InferCtxtExt as _;
use crate::traits::{self, ObligationCause, PredicateObligation};
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::sync::Lrc;
@@ -995,31 +994,37 @@ impl<'a, 'tcx> Instantiator<'a, 'tcx> {
debug!("generated new type inference var {:?}", ty_var.kind());
let item_bounds = tcx.explicit_item_bounds(def_id);
- debug!(?item_bounds);
- let bounds: Vec<_> =
- item_bounds.iter().map(|(bound, _)| bound.subst(tcx, substs)).collect();
- let param_env = tcx.param_env(def_id);
- let InferOk { value: bounds, obligations } = infcx.partially_normalize_associated_types_in(
- ObligationCause::misc(self.value_span, self.body_id),
- param_env,
- bounds,
- );
- self.obligations.extend(obligations);
+ self.obligations.reserve(item_bounds.len());
+ for (predicate, _) in item_bounds {
+ debug!(?predicate);
+ let predicate = predicate.subst(tcx, substs);
+ debug!(?predicate);
- debug!(?bounds);
+ // We can't normalize associated types from `rustc_infer`, but we can eagerly register inference variables for them.
+ let predicate = predicate.fold_with(&mut BottomUpFolder {
+ tcx,
+ ty_op: |ty| match ty.kind() {
+ ty::Projection(projection_ty) => infcx.infer_projection(
+ self.param_env,
+ *projection_ty,
+ ObligationCause::misc(self.value_span, self.body_id),
+ 0,
+ &mut self.obligations,
+ ),
+ _ => ty,
+ },
+ lt_op: |lt| lt,
+ ct_op: |ct| ct,
+ });
+ debug!(?predicate);
- for predicate in &bounds {
if let ty::PredicateKind::Projection(projection) = predicate.kind().skip_binder() {
if projection.ty.references_error() {
// No point on adding these obligations since there's a type error involved.
return ty_var;
}
}
- }
-
- self.obligations.reserve(bounds.len());
- for predicate in bounds {
// Change the predicate to refer to the type variable,
// which will be the concrete type instead of the opaque type.
// This also instantiates nested instances of `impl Trait`.
@@ -1029,7 +1034,7 @@ impl<'a, 'tcx> Instantiator<'a, 'tcx> {
traits::ObligationCause::new(self.value_span, self.body_id, traits::OpaqueType);
// Require that the predicate holds for the concrete type.
- debug!("instantiate_opaque_types: predicate={:?}", predicate);
+ debug!(?predicate);
self.obligations.push(traits::Obligation::new(cause, self.param_env, predicate));
}
diff --git a/src/test/ui/impl-trait/issue-72911.rs b/src/test/ui/impl-trait/issue-72911.rs
index dee5a41f6de..8761e4cf66a 100644
--- a/src/test/ui/impl-trait/issue-72911.rs
+++ b/src/test/ui/impl-trait/issue-72911.rs
@@ -16,6 +16,7 @@ fn gather_from_file(dir_entry: &foo::MissingItem) -> impl Iterator<Item = Lint>
fn lint_files() -> impl Iterator<Item = foo::MissingItem> {
//~^ ERROR: failed to resolve
+ //~| ERROR: `()` is not an iterator
unimplemented!()
}
diff --git a/src/test/ui/impl-trait/issue-72911.stderr b/src/test/ui/impl-trait/issue-72911.stderr
index 17748ae4277..6c6d9cbe23e 100644
--- a/src/test/ui/impl-trait/issue-72911.stderr
+++ b/src/test/ui/impl-trait/issue-72911.stderr
@@ -28,7 +28,15 @@ LL | fn gather_from_file(dir_entry: &foo::MissingItem) -> impl Iterator<Item = L
LL | fn lint_files() -> impl Iterator<Item = foo::MissingItem> {
| -------------------------------------- returning this opaque type `FlatMap<impl Iterator, [type error], [closure@$DIR/issue-72911.rs:9:27: 9:51]>`
-error: aborting due to 3 previous errors
+error[E0277]: `()` is not an iterator
+ --> $DIR/issue-72911.rs:17:20
+ |
+LL | fn lint_files() -> impl Iterator<Item = foo::MissingItem> {
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `()` is not an iterator
+ |
+ = help: the trait `Iterator` is not implemented for `()`
-Some errors have detailed explanations: E0433, E0720.
-For more information about an error, try `rustc --explain E0433`.
+error: aborting due to 4 previous errors
+
+Some errors have detailed explanations: E0277, E0433, E0720.
+For more information about an error, try `rustc --explain E0277`.