From a1e7495a41bac25797a7b82aee18f350e406bc2a Mon Sep 17 00:00:00 2001
From: Jonas Schievink <jonasschievink@gmail.com>
Date: Sat, 28 Mar 2020 21:15:45 +0100
Subject: [PATCH 1/7] Simplify `NodeItem`
The generic parameter is unused, and so is `map`
---
.../traits/specialization_graph.rs | 18 +++++++-----------
src/librustc_trait_selection/traits/project.rs | 2 +-
2 files changed, 8 insertions(+), 12 deletions(-)
diff --git a/src/librustc_middle/traits/specialization_graph.rs b/src/librustc_middle/traits/specialization_graph.rs
index 1847326a742eb..b09f1e66f1774 100644
--- a/src/librustc_middle/traits/specialization_graph.rs
+++ b/src/librustc_middle/traits/specialization_graph.rs
@@ -154,15 +154,9 @@ impl Iterator for Ancestors<'_> {
}
}
-pub struct NodeItem<T> {
+pub struct NodeItem {
pub node: Node,
- pub item: T,
-}
-
-impl<T> NodeItem<T> {
- pub fn map<U, F: FnOnce(T) -> U>(self, f: F) -> NodeItem<U> {
- NodeItem { node: self.node, item: f(self.item) }
- }
+ pub item: ty::AssocItem,
}
impl<'tcx> Ancestors<'tcx> {
@@ -173,7 +167,7 @@ impl<'tcx> Ancestors<'tcx> {
tcx: TyCtxt<'tcx>,
trait_item_name: Ident,
trait_item_kind: ty::AssocKind,
- ) -> Option<NodeItem<ty::AssocItem>> {
+ ) -> Option<NodeItem> {
let trait_def_id = self.trait_def_id;
self.find_map(|node| {
node.item(tcx, trait_item_name, trait_item_kind, trait_def_id)
@@ -183,8 +177,10 @@ impl<'tcx> Ancestors<'tcx> {
}
/// Walk up the specialization ancestors of a given impl, starting with that
-/// impl itself. Returns `None` if an error was reported while building the
-/// specialization graph.
+/// impl itself.
+///
+/// Returns `Err` if an error was reported while building the specialization
+/// graph.
pub fn ancestors(
tcx: TyCtxt<'tcx>,
trait_def_id: DefId,
diff --git a/src/librustc_trait_selection/traits/project.rs b/src/librustc_trait_selection/traits/project.rs
index 2eb63b8f59030..1e26b62c75951 100644
--- a/src/librustc_trait_selection/traits/project.rs
+++ b/src/librustc_trait_selection/traits/project.rs
@@ -1447,7 +1447,7 @@ fn assoc_ty_def(
selcx: &SelectionContext<'_, '_>,
impl_def_id: DefId,
assoc_ty_def_id: DefId,
-) -> Result<specialization_graph::NodeItem<ty::AssocItem>, ErrorReported> {
+) -> Result<specialization_graph::NodeItem, ErrorReported> {
let tcx = selcx.tcx();
let assoc_ty_name = tcx.associated_item(assoc_ty_def_id).ident;
let trait_def_id = tcx.impl_trait_ref(impl_def_id).unwrap().def_id;
From 49ba323c8db6fd5fbe3d72f623c9d89cb09c508d Mon Sep 17 00:00:00 2001
From: Jonas Schievink <jonasschievink@gmail.com>
Date: Sun, 29 Mar 2020 00:57:49 +0100
Subject: [PATCH 2/7] spec. graph: track defining and finalizing impls
---
src/librustc_middle/traits/mod.rs | 1 +
.../traits/specialization_graph.rs | 62 +++++++++++++++++--
src/librustc_middle/traits/util.rs | 17 +++++
src/librustc_trait_selection/traits/mod.rs | 3 +-
.../traits/project.rs | 48 ++++----------
.../traits/specialize/mod.rs | 2 +-
src/librustc_trait_selection/traits/util.rs | 16 +----
src/librustc_typeck/check/mod.rs | 7 ++-
8 files changed, 93 insertions(+), 63 deletions(-)
create mode 100644 src/librustc_middle/traits/util.rs
diff --git a/src/librustc_middle/traits/mod.rs b/src/librustc_middle/traits/mod.rs
index c129b574fd38a..d47e2d75fba35 100644
--- a/src/librustc_middle/traits/mod.rs
+++ b/src/librustc_middle/traits/mod.rs
@@ -6,6 +6,7 @@ pub mod query;
pub mod select;
pub mod specialization_graph;
mod structural_impls;
+pub mod util;
use crate::mir::interpret::ErrorHandled;
use crate::ty::subst::SubstsRef;
diff --git a/src/librustc_middle/traits/specialization_graph.rs b/src/librustc_middle/traits/specialization_graph.rs
index b09f1e66f1774..f66f94fe8c168 100644
--- a/src/librustc_middle/traits/specialization_graph.rs
+++ b/src/librustc_middle/traits/specialization_graph.rs
@@ -154,9 +154,45 @@ impl Iterator for Ancestors<'_> {
}
}
-pub struct NodeItem {
- pub node: Node,
+/// Information about the most specialized definition of an associated item.
+pub struct LeafDef {
+ /// The associated item described by this `LeafDef`.
pub item: ty::AssocItem,
+
+ /// The node in the specialization graph containing the definition of `item`.
+ pub defining_node: Node,
+
+ /// The "top-most" (ie. least specialized) specialization graph node that finalized the
+ /// definition of `item`.
+ ///
+ /// Example:
+ ///
+ /// ```
+ /// trait Tr {
+ /// fn assoc(&self);
+ /// }
+ ///
+ /// impl<T> Tr for T {
+ /// default fn assoc(&self) {}
+ /// }
+ ///
+ /// impl Tr for u8 {}
+ /// ```
+ ///
+ /// If we start the leaf definition search at `impl Tr for u8`, that impl will be the
+ /// `finalizing_node`, while `defining_node` will be the generic impl.
+ ///
+ /// If the leaf definition search is started at the generic impl, `finalizing_node` will be
+ /// `None`, since the most specialized impl we found still allows overriding the method
+ /// (doesn't finalize it).
+ pub finalizing_node: Option<Node>,
+}
+
+impl LeafDef {
+ /// Returns whether this definition is known to not be further specializable.
+ pub fn is_final(&self) -> bool {
+ self.finalizing_node.is_some()
+ }
}
impl<'tcx> Ancestors<'tcx> {
@@ -167,11 +203,27 @@ impl<'tcx> Ancestors<'tcx> {
tcx: TyCtxt<'tcx>,
trait_item_name: Ident,
trait_item_kind: ty::AssocKind,
- ) -> Option<NodeItem> {
+ ) -> Option<LeafDef> {
let trait_def_id = self.trait_def_id;
+ let mut finalizing_node = None;
+
self.find_map(|node| {
- node.item(tcx, trait_item_name, trait_item_kind, trait_def_id)
- .map(|item| NodeItem { node, item })
+ if let Some(item) = node.item(tcx, trait_item_name, trait_item_kind, trait_def_id) {
+ if finalizing_node.is_none() {
+ let is_specializable = item.defaultness.is_default()
+ || super::util::impl_is_default(tcx, node.def_id());
+
+ if !is_specializable {
+ finalizing_node = Some(node);
+ }
+ }
+
+ Some(LeafDef { item, defining_node: node, finalizing_node })
+ } else {
+ // Item not mentioned. This "finalizes" any defaulted item provided by an ancestor.
+ finalizing_node = Some(node);
+ None
+ }
})
}
}
diff --git a/src/librustc_middle/traits/util.rs b/src/librustc_middle/traits/util.rs
new file mode 100644
index 0000000000000..cb29cf0760ebc
--- /dev/null
+++ b/src/librustc_middle/traits/util.rs
@@ -0,0 +1,17 @@
+use crate::ty::TyCtxt;
+use rustc_hir as hir;
+use rustc_hir::def_id::DefId;
+
+pub fn impl_is_default(tcx: TyCtxt<'_>, node_item_def_id: DefId) -> bool {
+ match tcx.hir().as_local_hir_id(node_item_def_id) {
+ Some(hir_id) => {
+ let item = tcx.hir().expect_item(hir_id);
+ if let hir::ItemKind::Impl { defaultness, .. } = item.kind {
+ defaultness.is_default()
+ } else {
+ false
+ }
+ }
+ None => tcx.impl_defaultness(node_item_def_id).is_default(),
+ }
+}
diff --git a/src/librustc_trait_selection/traits/mod.rs b/src/librustc_trait_selection/traits/mod.rs
index 3ef44a198417a..d6204975a7bf2 100644
--- a/src/librustc_trait_selection/traits/mod.rs
+++ b/src/librustc_trait_selection/traits/mod.rs
@@ -64,8 +64,7 @@ pub use self::structural_match::NonStructuralMatchTy;
pub use self::util::{elaborate_predicates, elaborate_trait_ref, elaborate_trait_refs};
pub use self::util::{expand_trait_aliases, TraitAliasExpander};
pub use self::util::{
- get_vtable_index_of_object_method, impl_is_default, impl_item_is_final,
- predicate_for_trait_def, upcast_choices,
+ get_vtable_index_of_object_method, impl_item_is_final, predicate_for_trait_def, upcast_choices,
};
pub use self::util::{
supertrait_def_ids, supertraits, transitive_bounds, SupertraitDefIds, Supertraits,
diff --git a/src/librustc_trait_selection/traits/project.rs b/src/librustc_trait_selection/traits/project.rs
index 1e26b62c75951..cd89111a17712 100644
--- a/src/librustc_trait_selection/traits/project.rs
+++ b/src/librustc_trait_selection/traits/project.rs
@@ -1015,49 +1015,21 @@ fn assemble_candidates_from_impls<'cx, 'tcx>(
assoc_ty_def(selcx, impl_data.impl_def_id, obligation.predicate.item_def_id)
.map_err(|ErrorReported| ())?;
- let is_default = if node_item.node.is_from_trait() {
- // If true, the impl inherited a `type Foo = Bar`
- // given in the trait, which is implicitly default.
- // Otherwise, the impl did not specify `type` and
- // neither did the trait:
- //
- // ```rust
- // trait Foo { type T; }
- // impl Foo for Bar { }
- // ```
- //
- // This is an error, but it will be
- // reported in `check_impl_items_against_trait`.
- // We accept it here but will flag it as
- // an error when we confirm the candidate
- // (which will ultimately lead to `normalize_to_error`
- // being invoked).
- false
- } else {
- // If we're looking at a trait *impl*, the item is
- // specializable if the impl or the item are marked
- // `default`.
- node_item.item.defaultness.is_default()
- || super::util::impl_is_default(selcx.tcx(), node_item.node.def_id())
- };
-
- match is_default {
+ if node_item.is_final() {
// Non-specializable items are always projectable
- false => true,
-
+ true
+ } else {
// Only reveal a specializable default if we're past type-checking
// and the obligation is monomorphic, otherwise passes such as
// transmute checking and polymorphic MIR optimizations could
// get a result which isn't correct for all monomorphizations.
- true if obligation.param_env.reveal == Reveal::All => {
+ if obligation.param_env.reveal == Reveal::All {
// NOTE(eddyb) inference variables can resolve to parameters, so
// assume `poly_trait_ref` isn't monomorphic, if it contains any.
let poly_trait_ref =
selcx.infcx().resolve_vars_if_possible(&poly_trait_ref);
!poly_trait_ref.needs_infer() && !poly_trait_ref.needs_subst()
- }
-
- true => {
+ } else {
debug!(
"assemble_candidates_from_impls: not eligible due to default: \
assoc_ty={} predicate={}",
@@ -1422,7 +1394,8 @@ fn confirm_impl_candidate<'cx, 'tcx>(
return Progress { ty: tcx.types.err, obligations: nested };
}
let substs = obligation.predicate.substs.rebase_onto(tcx, trait_def_id, substs);
- let substs = translate_substs(selcx.infcx(), param_env, impl_def_id, substs, assoc_ty.node);
+ let substs =
+ translate_substs(selcx.infcx(), param_env, impl_def_id, substs, assoc_ty.defining_node);
let ty = if let ty::AssocKind::OpaqueTy = assoc_ty.item.kind {
let item_substs = InternalSubsts::identity_for_item(tcx, assoc_ty.item.def_id);
tcx.mk_opaque(assoc_ty.item.def_id, item_substs)
@@ -1447,7 +1420,7 @@ fn assoc_ty_def(
selcx: &SelectionContext<'_, '_>,
impl_def_id: DefId,
assoc_ty_def_id: DefId,
-) -> Result<specialization_graph::NodeItem, ErrorReported> {
+) -> Result<specialization_graph::LeafDef, ErrorReported> {
let tcx = selcx.tcx();
let assoc_ty_name = tcx.associated_item(assoc_ty_def_id).ident;
let trait_def_id = tcx.impl_trait_ref(impl_def_id).unwrap().def_id;
@@ -1464,9 +1437,10 @@ fn assoc_ty_def(
if matches!(item.kind, ty::AssocKind::Type | ty::AssocKind::OpaqueTy)
&& tcx.hygienic_eq(item.ident, assoc_ty_name, trait_def_id)
{
- return Ok(specialization_graph::NodeItem {
- node: specialization_graph::Node::Impl(impl_def_id),
+ return Ok(specialization_graph::LeafDef {
item: *item,
+ defining_node: impl_node,
+ finalizing_node: if item.defaultness.is_default() { None } else { Some(impl_node) },
});
}
}
diff --git a/src/librustc_trait_selection/traits/specialize/mod.rs b/src/librustc_trait_selection/traits/specialize/mod.rs
index edf02d75ee60f..f98d8f2fabf6a 100644
--- a/src/librustc_trait_selection/traits/specialize/mod.rs
+++ b/src/librustc_trait_selection/traits/specialize/mod.rs
@@ -141,7 +141,7 @@ pub fn find_associated_item<'tcx>(
param_env,
impl_data.impl_def_id,
substs,
- node_item.node,
+ node_item.defining_node,
);
infcx.tcx.erase_regions(&substs)
});
diff --git a/src/librustc_trait_selection/traits/util.rs b/src/librustc_trait_selection/traits/util.rs
index 6eeac2f676c09..c28628678a935 100644
--- a/src/librustc_trait_selection/traits/util.rs
+++ b/src/librustc_trait_selection/traits/util.rs
@@ -4,11 +4,11 @@ use smallvec::smallvec;
use smallvec::SmallVec;
use rustc_data_structures::fx::FxHashSet;
-use rustc_hir as hir;
use rustc_hir::def_id::DefId;
use rustc_middle::ty::outlives::Component;
use rustc_middle::ty::subst::{GenericArg, Subst, SubstsRef};
use rustc_middle::ty::{self, ToPolyTraitRef, ToPredicate, Ty, TyCtxt, WithConstness};
+use rustc_middle::traits::util::impl_is_default;
use super::{Normalized, Obligation, ObligationCause, PredicateObligation, SelectionContext};
@@ -651,20 +651,6 @@ pub fn generator_trait_ref_and_outputs(
ty::Binder::bind((trait_ref, sig.skip_binder().yield_ty, sig.skip_binder().return_ty))
}
-pub fn impl_is_default(tcx: TyCtxt<'_>, node_item_def_id: DefId) -> bool {
- match tcx.hir().as_local_hir_id(node_item_def_id) {
- Some(hir_id) => {
- let item = tcx.hir().expect_item(hir_id);
- if let hir::ItemKind::Impl { defaultness, .. } = item.kind {
- defaultness.is_default()
- } else {
- false
- }
- }
- None => tcx.impl_defaultness(node_item_def_id).is_default(),
- }
-}
-
pub fn impl_item_is_final(tcx: TyCtxt<'_>, assoc_item: &ty::AssocItem) -> bool {
assoc_item.defaultness.is_final() && !impl_is_default(tcx, assoc_item.container.id())
}
diff --git a/src/librustc_typeck/check/mod.rs b/src/librustc_typeck/check/mod.rs
index 6249e1d49779e..c85b5a4f2a258 100644
--- a/src/librustc_typeck/check/mod.rs
+++ b/src/librustc_typeck/check/mod.rs
@@ -110,6 +110,7 @@ use rustc_infer::infer::{self, InferCtxt, InferOk, InferResult, TyCtxtInferExt};
use rustc_middle::hir::map::blocks::FnLikeNode;
use rustc_middle::middle::region;
use rustc_middle::mir::interpret::ConstValue;
+use rustc_middle::traits::util::impl_is_default;
use rustc_middle::ty::adjustment::{
Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability, PointerCast,
};
@@ -1942,7 +1943,7 @@ fn check_specialization_validity<'tcx>(
// grandparent. In that case, if parent is a `default impl`, inherited items use the
// "defaultness" from the grandparent, else they are final.
None => {
- if traits::impl_is_default(tcx, parent_impl.def_id()) {
+ if impl_is_default(tcx, parent_impl.def_id()) {
None
} else {
Some(Err(parent_impl.def_id()))
@@ -2114,10 +2115,10 @@ fn check_impl_items_against_trait<'tcx>(
for trait_item in tcx.associated_items(impl_trait_ref.def_id).in_definition_order() {
let is_implemented = ancestors
.leaf_def(tcx, trait_item.ident, trait_item.kind)
- .map(|node_item| !node_item.node.is_from_trait())
+ .map(|node_item| !node_item.defining_node.is_from_trait())
.unwrap_or(false);
- if !is_implemented && !traits::impl_is_default(tcx, impl_id) {
+ if !is_implemented && !impl_is_default(tcx, impl_id) {
if !trait_item.defaultness.has_value() {
missing_items.push(*trait_item);
}
From 103771ce57acc240bc01abf4f7365172935bc7fb Mon Sep 17 00:00:00 2001
From: Jonas Schievink <jonasschievink@gmail.com>
Date: Sun, 29 Mar 2020 01:01:32 +0100
Subject: [PATCH 3/7] Add a test
---
src/test/ui/specialization/issue-70442.rs | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
create mode 100644 src/test/ui/specialization/issue-70442.rs
diff --git a/src/test/ui/specialization/issue-70442.rs b/src/test/ui/specialization/issue-70442.rs
new file mode 100644
index 0000000000000..4371dd2e16747
--- /dev/null
+++ b/src/test/ui/specialization/issue-70442.rs
@@ -0,0 +1,23 @@
+#![feature(specialization)]
+
+// check-pass
+
+trait Trait {
+ type Assoc;
+}
+
+impl<T> Trait for T {
+ default type Assoc = bool;
+}
+
+// This impl inherits the `Assoc` definition from above and "locks it in", or finalizes it, making
+// child impls unable to further specialize it. However, since the specialization graph didn't
+// correctly track this, we would refuse to project `Assoc` from this impl, even though that should
+// happen for items that are final.
+impl Trait for () {}
+
+fn foo<X: Trait<Assoc=bool>>() {}
+
+fn main() {
+ foo::<()>(); // `<() as Trait>::Assoc` is normalized to `bool` correctly
+}
From e8910f51d804438b6ed161a27e21dd272d9e969a Mon Sep 17 00:00:00 2001
From: Jonas Schievink <jonasschievink@gmail.com>
Date: Sun, 29 Mar 2020 16:40:30 +0200
Subject: [PATCH 4/7] Sync `Instance::resolve` with the projection code
---
src/librustc_trait_selection/traits/mod.rs | 1 -
.../traits/project.rs | 2 +-
.../traits/specialize/mod.rs | 44 +-----------------
src/librustc_ty/instance.rs | 46 +++++++++++++++----
4 files changed, 40 insertions(+), 53 deletions(-)
diff --git a/src/librustc_trait_selection/traits/mod.rs b/src/librustc_trait_selection/traits/mod.rs
index d6204975a7bf2..5f98850633075 100644
--- a/src/librustc_trait_selection/traits/mod.rs
+++ b/src/librustc_trait_selection/traits/mod.rs
@@ -54,7 +54,6 @@ pub use self::project::{
};
pub use self::select::{EvaluationCache, SelectionCache, SelectionContext};
pub use self::select::{EvaluationResult, IntercrateAmbiguityCause, OverflowError};
-pub use self::specialize::find_associated_item;
pub use self::specialize::specialization_graph::FutureCompatOverlapError;
pub use self::specialize::specialization_graph::FutureCompatOverlapErrorKind;
pub use self::specialize::{specialization_graph, translate_substs, OverlapError};
diff --git a/src/librustc_trait_selection/traits/project.rs b/src/librustc_trait_selection/traits/project.rs
index cd89111a17712..aae0d46756331 100644
--- a/src/librustc_trait_selection/traits/project.rs
+++ b/src/librustc_trait_selection/traits/project.rs
@@ -1016,7 +1016,7 @@ fn assemble_candidates_from_impls<'cx, 'tcx>(
.map_err(|ErrorReported| ())?;
if node_item.is_final() {
- // Non-specializable items are always projectable
+ // Non-specializable items are always projectable.
true
} else {
// Only reveal a specializable default if we're past type-checking
diff --git a/src/librustc_trait_selection/traits/specialize/mod.rs b/src/librustc_trait_selection/traits/specialize/mod.rs
index f98d8f2fabf6a..fabd8c89b72af 100644
--- a/src/librustc_trait_selection/traits/specialize/mod.rs
+++ b/src/librustc_trait_selection/traits/specialize/mod.rs
@@ -20,7 +20,7 @@ use rustc_errors::struct_span_err;
use rustc_hir::def_id::DefId;
use rustc_middle::lint::LintDiagnosticBuilder;
use rustc_middle::ty::subst::{InternalSubsts, Subst, SubstsRef};
-use rustc_middle::ty::{self, TyCtxt, TypeFoldable};
+use rustc_middle::ty::{self, TyCtxt};
use rustc_session::lint::builtin::COHERENCE_LEAK_CHECK;
use rustc_session::lint::builtin::ORDER_DEPENDENT_TRAIT_OBJECTS;
use rustc_span::DUMMY_SP;
@@ -112,48 +112,6 @@ pub fn translate_substs<'a, 'tcx>(
source_substs.rebase_onto(infcx.tcx, source_impl, target_substs)
}
-/// Given a selected impl described by `impl_data`, returns the
-/// definition and substitutions for the method with the name `name`
-/// the kind `kind`, and trait method substitutions `substs`, in
-/// that impl, a less specialized impl, or the trait default,
-/// whichever applies.
-pub fn find_associated_item<'tcx>(
- tcx: TyCtxt<'tcx>,
- param_env: ty::ParamEnv<'tcx>,
- item: &ty::AssocItem,
- substs: SubstsRef<'tcx>,
- impl_data: &super::VtableImplData<'tcx, ()>,
-) -> (DefId, SubstsRef<'tcx>) {
- debug!("find_associated_item({:?}, {:?}, {:?}, {:?})", param_env, item, substs, impl_data);
- assert!(!substs.needs_infer());
-
- let trait_def_id = tcx.trait_id_of_impl(impl_data.impl_def_id).unwrap();
- let trait_def = tcx.trait_def(trait_def_id);
-
- if let Ok(ancestors) = trait_def.ancestors(tcx, impl_data.impl_def_id) {
- match ancestors.leaf_def(tcx, item.ident, item.kind) {
- Some(node_item) => {
- let substs = tcx.infer_ctxt().enter(|infcx| {
- let param_env = param_env.with_reveal_all();
- let substs = substs.rebase_onto(tcx, trait_def_id, impl_data.substs);
- let substs = translate_substs(
- &infcx,
- param_env,
- impl_data.impl_def_id,
- substs,
- node_item.defining_node,
- );
- infcx.tcx.erase_regions(&substs)
- });
- (node_item.item.def_id, substs)
- }
- None => bug!("{:?} not found in {:?}", item, impl_data.impl_def_id),
- }
- } else {
- (item.def_id, substs)
- }
-}
-
/// Is `impl1` a specialization of `impl2`?
///
/// Specialization is determined by the sets of types to which the impls apply;
diff --git a/src/librustc_ty/instance.rs b/src/librustc_ty/instance.rs
index 447c49e40fb5a..2b7d7e7e63771 100644
--- a/src/librustc_ty/instance.rs
+++ b/src/librustc_ty/instance.rs
@@ -1,9 +1,11 @@
use rustc_hir::def_id::DefId;
use rustc_middle::ty::subst::SubstsRef;
use rustc_middle::ty::{self, Instance, TyCtxt, TypeFoldable};
+use rustc_infer::infer::TyCtxtInferExt;
use rustc_span::sym;
use rustc_target::spec::abi::Abi;
use rustc_trait_selection::traits;
+use traits::{Reveal, translate_substs};
use log::debug;
@@ -82,21 +84,49 @@ fn resolve_associated_item<'tcx>(
// the actual function:
match vtbl {
traits::VtableImpl(impl_data) => {
- let (def_id, substs) =
- traits::find_associated_item(tcx, param_env, trait_item, rcvr_substs, &impl_data);
-
- let resolved_item = tcx.associated_item(def_id);
+ debug!(
+ "resolving VtableImpl: {:?}, {:?}, {:?}, {:?}",
+ param_env, trait_item, rcvr_substs, impl_data
+ );
+ assert!(!rcvr_substs.needs_infer());
+
+ let trait_def_id = tcx.trait_id_of_impl(impl_data.impl_def_id).unwrap();
+ let trait_def = tcx.trait_def(trait_def_id);
+ let leaf_def = trait_def
+ .ancestors(tcx, impl_data.impl_def_id)
+ .ok()?
+ .leaf_def(tcx, trait_item.ident, trait_item.kind)
+ .unwrap_or_else(|| {
+ bug!("{:?} not found in {:?}", trait_item, impl_data.impl_def_id);
+ });
+ let def_id = leaf_def.item.def_id;
+
+ let substs = tcx.infer_ctxt().enter(|infcx| {
+ let param_env = param_env.with_reveal_all();
+ let substs = rcvr_substs.rebase_onto(tcx, trait_def_id, impl_data.substs);
+ let substs = translate_substs(
+ &infcx,
+ param_env,
+ impl_data.impl_def_id,
+ substs,
+ leaf_def.defining_node,
+ );
+ infcx.tcx.erase_regions(&substs)
+ });
// Since this is a trait item, we need to see if the item is either a trait default item
// or a specialization because we can't resolve those unless we can `Reveal::All`.
// NOTE: This should be kept in sync with the similar code in
// `rustc_middle::traits::project::assemble_candidates_from_impls()`.
- let eligible = if !resolved_item.defaultness.is_default() {
+ let eligible = if leaf_def.is_final() {
+ // Non-specializable items are always projectable.
true
- } else if param_env.reveal == traits::Reveal::All {
- !trait_ref.needs_subst()
} else {
- false
+ // Only reveal a specializable default if we're past type-checking
+ // and the obligation is monomorphic, otherwise passes such as
+ // transmute checking and polymorphic MIR optimizations could
+ // get a result which isn't correct for all monomorphizations.
+ if param_env.reveal == Reveal::All { !trait_ref.needs_subst() } else { false }
};
if !eligible {
From b00ba382e06aff8aae4ef6ba927ce53a4efd6f25 Mon Sep 17 00:00:00 2001
From: Jonas Schievink <jonasschievink@gmail.com>
Date: Sun, 29 Mar 2020 20:01:14 +0200
Subject: [PATCH 5/7] Use query instead of `impl_is_default` fn
---
src/librustc_middle/traits/mod.rs | 1 -
.../traits/specialization_graph.rs | 2 +-
src/librustc_middle/traits/util.rs | 17 -----------------
src/librustc_trait_selection/traits/util.rs | 3 +--
src/librustc_ty/ty.rs | 11 +++++++++++
src/librustc_typeck/check/mod.rs | 5 ++---
6 files changed, 15 insertions(+), 24 deletions(-)
delete mode 100644 src/librustc_middle/traits/util.rs
diff --git a/src/librustc_middle/traits/mod.rs b/src/librustc_middle/traits/mod.rs
index d47e2d75fba35..c129b574fd38a 100644
--- a/src/librustc_middle/traits/mod.rs
+++ b/src/librustc_middle/traits/mod.rs
@@ -6,7 +6,6 @@ pub mod query;
pub mod select;
pub mod specialization_graph;
mod structural_impls;
-pub mod util;
use crate::mir::interpret::ErrorHandled;
use crate::ty::subst::SubstsRef;
diff --git a/src/librustc_middle/traits/specialization_graph.rs b/src/librustc_middle/traits/specialization_graph.rs
index f66f94fe8c168..a2793f9805004 100644
--- a/src/librustc_middle/traits/specialization_graph.rs
+++ b/src/librustc_middle/traits/specialization_graph.rs
@@ -211,7 +211,7 @@ impl<'tcx> Ancestors<'tcx> {
if let Some(item) = node.item(tcx, trait_item_name, trait_item_kind, trait_def_id) {
if finalizing_node.is_none() {
let is_specializable = item.defaultness.is_default()
- || super::util::impl_is_default(tcx, node.def_id());
+ || tcx.impl_defaultness(node.def_id()).is_default();
if !is_specializable {
finalizing_node = Some(node);
diff --git a/src/librustc_middle/traits/util.rs b/src/librustc_middle/traits/util.rs
deleted file mode 100644
index cb29cf0760ebc..0000000000000
--- a/src/librustc_middle/traits/util.rs
+++ /dev/null
@@ -1,17 +0,0 @@
-use crate::ty::TyCtxt;
-use rustc_hir as hir;
-use rustc_hir::def_id::DefId;
-
-pub fn impl_is_default(tcx: TyCtxt<'_>, node_item_def_id: DefId) -> bool {
- match tcx.hir().as_local_hir_id(node_item_def_id) {
- Some(hir_id) => {
- let item = tcx.hir().expect_item(hir_id);
- if let hir::ItemKind::Impl { defaultness, .. } = item.kind {
- defaultness.is_default()
- } else {
- false
- }
- }
- None => tcx.impl_defaultness(node_item_def_id).is_default(),
- }
-}
diff --git a/src/librustc_trait_selection/traits/util.rs b/src/librustc_trait_selection/traits/util.rs
index c28628678a935..6348673dab8b5 100644
--- a/src/librustc_trait_selection/traits/util.rs
+++ b/src/librustc_trait_selection/traits/util.rs
@@ -8,7 +8,6 @@ use rustc_hir::def_id::DefId;
use rustc_middle::ty::outlives::Component;
use rustc_middle::ty::subst::{GenericArg, Subst, SubstsRef};
use rustc_middle::ty::{self, ToPolyTraitRef, ToPredicate, Ty, TyCtxt, WithConstness};
-use rustc_middle::traits::util::impl_is_default;
use super::{Normalized, Obligation, ObligationCause, PredicateObligation, SelectionContext};
@@ -652,7 +651,7 @@ pub fn generator_trait_ref_and_outputs(
}
pub fn impl_item_is_final(tcx: TyCtxt<'_>, assoc_item: &ty::AssocItem) -> bool {
- assoc_item.defaultness.is_final() && !impl_is_default(tcx, assoc_item.container.id())
+ assoc_item.defaultness.is_final() && tcx.impl_defaultness(assoc_item.container.id()).is_final()
}
pub enum TupleArgumentsFlag {
diff --git a/src/librustc_ty/ty.rs b/src/librustc_ty/ty.rs
index 9d28447e212a6..aefe61f60b87a 100644
--- a/src/librustc_ty/ty.rs
+++ b/src/librustc_ty/ty.rs
@@ -165,6 +165,16 @@ fn associated_item(tcx: TyCtxt<'_>, def_id: DefId) -> ty::AssocItem {
)
}
+fn impl_defaultness(tcx: TyCtxt<'_>, def_id: DefId) -> hir::Defaultness {
+ let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
+ let item = tcx.hir().expect_item(hir_id);
+ if let hir::ItemKind::Impl { defaultness, .. } = item.kind {
+ defaultness
+ } else {
+ bug!("`impl_defaultness` called on {:?}", item);
+ }
+}
+
/// Calculates the `Sized` constraint.
///
/// In fact, there are only a few options for the types in the constraint:
@@ -371,6 +381,7 @@ pub fn provide(providers: &mut ty::query::Providers<'_>) {
crate_hash,
instance_def_size_estimate,
issue33140_self_ty,
+ impl_defaultness,
..*providers
};
}
diff --git a/src/librustc_typeck/check/mod.rs b/src/librustc_typeck/check/mod.rs
index c85b5a4f2a258..3823efe9d927e 100644
--- a/src/librustc_typeck/check/mod.rs
+++ b/src/librustc_typeck/check/mod.rs
@@ -110,7 +110,6 @@ use rustc_infer::infer::{self, InferCtxt, InferOk, InferResult, TyCtxtInferExt};
use rustc_middle::hir::map::blocks::FnLikeNode;
use rustc_middle::middle::region;
use rustc_middle::mir::interpret::ConstValue;
-use rustc_middle::traits::util::impl_is_default;
use rustc_middle::ty::adjustment::{
Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability, PointerCast,
};
@@ -1943,7 +1942,7 @@ fn check_specialization_validity<'tcx>(
// grandparent. In that case, if parent is a `default impl`, inherited items use the
// "defaultness" from the grandparent, else they are final.
None => {
- if impl_is_default(tcx, parent_impl.def_id()) {
+ if tcx.impl_defaultness(parent_impl.def_id()).is_default() {
None
} else {
Some(Err(parent_impl.def_id()))
@@ -2118,7 +2117,7 @@ fn check_impl_items_against_trait<'tcx>(
.map(|node_item| !node_item.defining_node.is_from_trait())
.unwrap_or(false);
- if !is_implemented && !impl_is_default(tcx, impl_id) {
+ if !is_implemented && tcx.impl_defaultness(impl_id).is_final() {
if !trait_item.defaultness.has_value() {
missing_items.push(*trait_item);
}
From 12d9f4efaf972c4da1192dda4f43c19c8983bc79 Mon Sep 17 00:00:00 2001
From: Jonas Schievink <jonasschievink@gmail.com>
Date: Sun, 29 Mar 2020 20:01:41 +0200
Subject: [PATCH 6/7] Assert that the trait ref does not need inference
---
src/librustc_ty/instance.rs | 1 +
1 file changed, 1 insertion(+)
diff --git a/src/librustc_ty/instance.rs b/src/librustc_ty/instance.rs
index 2b7d7e7e63771..2d16f1f1d3a2c 100644
--- a/src/librustc_ty/instance.rs
+++ b/src/librustc_ty/instance.rs
@@ -89,6 +89,7 @@ fn resolve_associated_item<'tcx>(
param_env, trait_item, rcvr_substs, impl_data
);
assert!(!rcvr_substs.needs_infer());
+ assert!(!trait_ref.needs_infer());
let trait_def_id = tcx.trait_id_of_impl(impl_data.impl_def_id).unwrap();
let trait_def = tcx.trait_def(trait_def_id);
From fd8f8189d3323737a06285c9a4b926fefc9411fa Mon Sep 17 00:00:00 2001
From: Jonas Schievink <jonasschievink@gmail.com>
Date: Mon, 30 Mar 2020 21:40:53 +0200
Subject: [PATCH 7/7] Format
---
src/librustc_ty/instance.rs | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/src/librustc_ty/instance.rs b/src/librustc_ty/instance.rs
index 2d16f1f1d3a2c..47c4b1c41cdbd 100644
--- a/src/librustc_ty/instance.rs
+++ b/src/librustc_ty/instance.rs
@@ -1,11 +1,11 @@
use rustc_hir::def_id::DefId;
+use rustc_infer::infer::TyCtxtInferExt;
use rustc_middle::ty::subst::SubstsRef;
use rustc_middle::ty::{self, Instance, TyCtxt, TypeFoldable};
-use rustc_infer::infer::TyCtxtInferExt;
use rustc_span::sym;
use rustc_target::spec::abi::Abi;
use rustc_trait_selection::traits;
-use traits::{Reveal, translate_substs};
+use traits::{translate_substs, Reveal};
use log::debug;