From 13d3e57237eefd92a518d99367b6f8e04110e847 Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Fri, 4 Aug 2023 23:54:14 +0000
Subject: [PATCH 1/4] RPITITs capture all their lifetimes
---
compiler/rustc_ast_lowering/src/lib.rs | 53 ++++++++-------
compiler/rustc_resolve/src/late.rs | 21 +++---
.../impl-trait/in-trait/object-safety.stderr | 13 +++-
.../in-trait/signature-mismatch.stderr | 65 +++----------------
4 files changed, 60 insertions(+), 92 deletions(-)
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index 1827e42368f92..a4ba1a5c9bf48 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -236,7 +236,7 @@ enum ImplTraitContext {
ReturnPositionOpaqueTy {
/// Origin: Either OpaqueTyOrigin::FnReturn or OpaqueTyOrigin::AsyncFn,
origin: hir::OpaqueTyOrigin,
- in_trait: bool,
+ fn_kind: FnDeclKind,
},
/// Impl trait in type aliases.
TypeAliasesOpaqueTy { in_assoc_ty: bool },
@@ -312,7 +312,7 @@ impl std::fmt::Display for ImplTraitPosition {
}
}
-#[derive(Debug, PartialEq, Eq)]
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
enum FnDeclKind {
Fn,
Inherent,
@@ -1401,13 +1401,13 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
TyKind::ImplTrait(def_node_id, bounds) => {
let span = t.span;
match itctx {
- ImplTraitContext::ReturnPositionOpaqueTy { origin, in_trait } => self
+ ImplTraitContext::ReturnPositionOpaqueTy { origin, fn_kind } => self
.lower_opaque_impl_trait(
span,
*origin,
*def_node_id,
bounds,
- *in_trait,
+ Some(*fn_kind),
itctx,
),
&ImplTraitContext::TypeAliasesOpaqueTy { in_assoc_ty } => self
@@ -1416,7 +1416,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
hir::OpaqueTyOrigin::TyAlias { in_assoc_ty },
*def_node_id,
bounds,
- false,
+ None,
itctx,
),
ImplTraitContext::Universal => {
@@ -1523,7 +1523,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
origin: hir::OpaqueTyOrigin,
opaque_ty_node_id: NodeId,
bounds: &GenericBounds,
- in_trait: bool,
+ fn_kind: Option<FnDeclKind>,
itctx: &ImplTraitContext,
) -> hir::TyKind<'hir> {
// Make sure we know that some funky desugaring has been going on here.
@@ -1540,10 +1540,22 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
Vec::new()
}
hir::OpaqueTyOrigin::FnReturn(..) => {
- // in fn return position, like the `fn test<'a>() -> impl Debug + 'a`
- // example, we only need to duplicate lifetimes that appear in the
- // bounds, since those are the only ones that are captured by the opaque.
- lifetime_collector::lifetimes_in_bounds(&self.resolver, bounds)
+ if let FnDeclKind::Impl | FnDeclKind::Trait =
+ fn_kind.expect("expected RPITs to be lowered with a FnKind")
+ {
+ // return-position impl trait in trait was decided to capture all
+ // in-scope lifetimes, which we collect for all opaques during resolution.
+ self.resolver
+ .take_extra_lifetime_params(opaque_ty_node_id)
+ .into_iter()
+ .map(|(ident, id, _)| Lifetime { id, ident })
+ .collect()
+ } else {
+ // in fn return position, like the `fn test<'a>() -> impl Debug + 'a`
+ // example, we only need to duplicate lifetimes that appear in the
+ // bounds, since those are the only ones that are captured by the opaque.
+ lifetime_collector::lifetimes_in_bounds(&self.resolver, bounds)
+ }
}
hir::OpaqueTyOrigin::AsyncFn(..) => {
unreachable!("should be using `lower_async_fn_ret_ty`")
@@ -1554,7 +1566,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
self.lower_opaque_inner(
opaque_ty_node_id,
origin,
- in_trait,
+ matches!(fn_kind, Some(FnDeclKind::Trait)),
captured_lifetimes_to_duplicate,
span,
opaque_ty_span,
@@ -1802,12 +1814,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
}
let fn_def_id = self.local_def_id(fn_node_id);
- self.lower_async_fn_ret_ty(
- &decl.output,
- fn_def_id,
- ret_id,
- matches!(kind, FnDeclKind::Trait),
- )
+ self.lower_async_fn_ret_ty(&decl.output, fn_def_id, ret_id, kind)
} else {
match &decl.output {
FnRetTy::Ty(ty) => {
@@ -1815,7 +1822,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
let fn_def_id = self.local_def_id(fn_node_id);
ImplTraitContext::ReturnPositionOpaqueTy {
origin: hir::OpaqueTyOrigin::FnReturn(fn_def_id),
- in_trait: matches!(kind, FnDeclKind::Trait),
+ fn_kind: kind,
}
} else {
let position = match kind {
@@ -1883,7 +1890,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
output: &FnRetTy,
fn_def_id: LocalDefId,
opaque_ty_node_id: NodeId,
- in_trait: bool,
+ fn_kind: FnDeclKind,
) -> hir::FnRetTy<'hir> {
let span = self.lower_span(output.span());
let opaque_ty_span = self.mark_span_with_reason(DesugaringKind::Async, span, None);
@@ -1898,7 +1905,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
let opaque_ty_ref = self.lower_opaque_inner(
opaque_ty_node_id,
hir::OpaqueTyOrigin::AsyncFn(fn_def_id),
- in_trait,
+ matches!(fn_kind, FnDeclKind::Trait),
captured_lifetimes,
span,
opaque_ty_span,
@@ -1906,7 +1913,9 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
let future_bound = this.lower_async_fn_output_type_to_future_bound(
output,
span,
- if in_trait && !this.tcx.features().return_position_impl_trait_in_trait {
+ if let FnDeclKind::Trait = fn_kind
+ && !this.tcx.features().return_position_impl_trait_in_trait
+ {
ImplTraitContext::FeatureGated(
ImplTraitPosition::TraitReturn,
sym::return_position_impl_trait_in_trait,
@@ -1914,7 +1923,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
} else {
ImplTraitContext::ReturnPositionOpaqueTy {
origin: hir::OpaqueTyOrigin::FnReturn(fn_def_id),
- in_trait,
+ fn_kind,
}
},
);
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
index 22d084c8e0b5c..500004269c927 100644
--- a/compiler/rustc_resolve/src/late.rs
+++ b/compiler/rustc_resolve/src/late.rs
@@ -772,9 +772,10 @@ impl<'a: 'ast, 'ast, 'tcx> Visitor<'ast> for LateResolutionVisitor<'a, '_, 'ast,
self.r.record_partial_res(ty.id, PartialRes::new(res));
visit::walk_ty(self, ty)
}
- TyKind::ImplTrait(..) => {
+ TyKind::ImplTrait(node_id, _) => {
let candidates = self.lifetime_elision_candidates.take();
visit::walk_ty(self, ty);
+ self.record_lifetime_params_for_impl_trait(*node_id);
self.lifetime_elision_candidates = candidates;
}
TyKind::TraitObject(bounds, ..) => {
@@ -909,8 +910,8 @@ impl<'a: 'ast, 'ast, 'tcx> Visitor<'ast> for LateResolutionVisitor<'a, '_, 'ast,
&sig.decl.output,
);
- if let Some((async_node_id, span)) = sig.header.asyncness.opt_return_id() {
- this.record_lifetime_params_for_impl_trait(async_node_id, span);
+ if let Some((async_node_id, _)) = sig.header.asyncness.opt_return_id() {
+ this.record_lifetime_params_for_impl_trait(async_node_id);
}
},
);
@@ -951,8 +952,8 @@ impl<'a: 'ast, 'ast, 'tcx> Visitor<'ast> for LateResolutionVisitor<'a, '_, 'ast,
&declaration.output,
);
- if let Some((async_node_id, span)) = async_node_id {
- this.record_lifetime_params_for_impl_trait(async_node_id, span);
+ if let Some((async_node_id, _)) = async_node_id {
+ this.record_lifetime_params_for_impl_trait(async_node_id);
}
},
);
@@ -4367,7 +4368,7 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
/// We include all lifetime parameters, either named or "Fresh".
/// The order of those parameters does not matter, as long as it is
/// deterministic.
- fn record_lifetime_params_for_impl_trait(&mut self, impl_trait_node_id: NodeId, span: Span) {
+ fn record_lifetime_params_for_impl_trait(&mut self, impl_trait_node_id: NodeId) {
let mut extra_lifetime_params = vec![];
for rib in self.lifetime_ribs.iter().rev() {
@@ -4380,14 +4381,10 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
extra_lifetime_params.extend(earlier_fresh);
}
}
- LifetimeRibKind::Generics { .. } => {}
- _ => {
- // We are in a function definition. We should only find `Generics`
- // and `AnonymousCreateParameter` inside the innermost `Item`.
- span_bug!(span, "unexpected rib kind: {:?}", rib.kind)
- }
+ _ => {}
}
}
+
self.r.extra_lifetime_params_map.insert(impl_trait_node_id, extra_lifetime_params);
}
diff --git a/tests/ui/impl-trait/in-trait/object-safety.stderr b/tests/ui/impl-trait/in-trait/object-safety.stderr
index 4a3b3b11465a1..1eb063a5fc2e7 100644
--- a/tests/ui/impl-trait/in-trait/object-safety.stderr
+++ b/tests/ui/impl-trait/in-trait/object-safety.stderr
@@ -13,6 +13,14 @@ LL | fn baz(&self) -> impl Debug;
| ^^^^^^^^^^ ...because method `baz` references an `impl Trait` type in its return type
= help: consider moving `baz` to another trait
+error[E0277]: the trait bound `dyn Foo: Foo` is not satisfied
+ --> $DIR/object-safety.rs:20:15
+ |
+LL | let s = i.baz();
+ | ^^^ the trait `Foo` is not implemented for `dyn Foo`
+ |
+ = help: the trait `Foo` is implemented for `u32`
+
error[E0038]: the trait `Foo` cannot be made into an object
--> $DIR/object-safety.rs:20:13
|
@@ -44,6 +52,7 @@ LL | fn baz(&self) -> impl Debug;
= help: consider moving `baz` to another trait
= note: required for the cast from `Box<u32>` to `Box<dyn Foo>`
-error: aborting due to 3 previous errors
+error: aborting due to 4 previous errors
-For more information about this error, try `rustc --explain E0038`.
+Some errors have detailed explanations: E0038, E0277.
+For more information about an error, try `rustc --explain E0038`.
diff --git a/tests/ui/impl-trait/in-trait/signature-mismatch.stderr b/tests/ui/impl-trait/in-trait/signature-mismatch.stderr
index 616f1ac35a953..05b5d3f11489f 100644
--- a/tests/ui/impl-trait/in-trait/signature-mismatch.stderr
+++ b/tests/ui/impl-trait/in-trait/signature-mismatch.stderr
@@ -1,61 +1,14 @@
-error: return type captures more lifetimes than trait definition
- --> $DIR/signature-mismatch.rs:34:47
- |
-LL | fn async_fn<'a>(&self, buff: &'a [u8]) -> impl Future<Output = Vec<u8>> + 'a {
- | -- this lifetime was captured ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
- |
-note: hidden type must only reference lifetimes captured by this impl trait
- --> $DIR/signature-mismatch.rs:15:40
- |
-LL | fn async_fn(&self, buff: &[u8]) -> impl Future<Output = Vec<u8>>;
- | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
- = note: hidden type inferred to be `impl Future<Output = Vec<u8>> + 'a`
-
-error: return type captures more lifetimes than trait definition
- --> $DIR/signature-mismatch.rs:39:57
- |
-LL | fn async_fn_early<'a: 'a>(&self, buff: &'a [u8]) -> impl Future<Output = Vec<u8>> + 'a {
- | -- this lifetime was captured ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
- |
-note: hidden type must only reference lifetimes captured by this impl trait
- --> $DIR/signature-mismatch.rs:16:57
- |
-LL | fn async_fn_early<'a: 'a>(&self, buff: &'a [u8]) -> impl Future<Output = Vec<u8>>;
- | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
- = note: hidden type inferred to be `impl Future<Output = Vec<u8>> + 'a`
-
-error: return type captures more lifetimes than trait definition
- --> $DIR/signature-mismatch.rs:47:10
- |
-LL | fn async_fn_multiple<'a, 'b>(
- | -- this lifetime was captured
-...
-LL | ) -> impl Future<Output = Vec<u8>> + Captures2<'a, 'b> {
- | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
- |
-note: hidden type must only reference lifetimes captured by this impl trait
- --> $DIR/signature-mismatch.rs:18:12
- |
-LL | -> impl Future<Output = Vec<u8>> + Captures<'a>;
- | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
- = note: hidden type inferred to be `impl Future<Output = Vec<u8>> + Captures2<'a, 'b>`
-
-error[E0309]: the parameter type `T` may not live long enough
+error[E0623]: lifetime mismatch
--> $DIR/signature-mismatch.rs:56:10
|
+LL | &'a self,
+ | -------- this parameter and the return type are declared with different lifetimes...
+...
LL | ) -> impl Future<Output = Vec<u8>> {
- | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ...so that the type `impl Future<Output = Vec<u8>>` will meet its required lifetime bounds...
- |
-note: ...that is required by this bound
- --> $DIR/signature-mismatch.rs:23:42
- |
-LL | ) -> impl Future<Output = Vec<u8>> + 'a;
- | ^^
-help: consider adding an explicit lifetime bound...
- |
-LL | fn async_fn_reduce_outlive<'a, 'b, T: 'a>(
- | ++++
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ | |
+ | ...but data from `buff` is returned here
-error: aborting due to 4 previous errors
+error: aborting due to previous error
-For more information about this error, try `rustc --explain E0309`.
+For more information about this error, try `rustc --explain E0623`.
From 32a9565223c05e6f7e60d783ad25e1864cd51d70 Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Tue, 8 Aug 2023 19:37:35 +0000
Subject: [PATCH 2/4] Bless tests
---
tests/ui/impl-trait/in-trait/object-safety.rs | 1 +
...derr => signature-mismatch.failure.stderr} | 2 +-
.../impl-trait/in-trait/signature-mismatch.rs | 38 +++++++++++++++----
3 files changed, 32 insertions(+), 9 deletions(-)
rename tests/ui/impl-trait/in-trait/{signature-mismatch.stderr => signature-mismatch.failure.stderr} (91%)
diff --git a/tests/ui/impl-trait/in-trait/object-safety.rs b/tests/ui/impl-trait/in-trait/object-safety.rs
index dd35b9a2d8a75..6e02934363d56 100644
--- a/tests/ui/impl-trait/in-trait/object-safety.rs
+++ b/tests/ui/impl-trait/in-trait/object-safety.rs
@@ -19,4 +19,5 @@ fn main() {
//~| ERROR the trait `Foo` cannot be made into an object
let s = i.baz();
//~^ ERROR the trait `Foo` cannot be made into an object
+ //~| ERROR the trait bound `dyn Foo: Foo`
}
diff --git a/tests/ui/impl-trait/in-trait/signature-mismatch.stderr b/tests/ui/impl-trait/in-trait/signature-mismatch.failure.stderr
similarity index 91%
rename from tests/ui/impl-trait/in-trait/signature-mismatch.stderr
rename to tests/ui/impl-trait/in-trait/signature-mismatch.failure.stderr
index 05b5d3f11489f..186580f57566d 100644
--- a/tests/ui/impl-trait/in-trait/signature-mismatch.stderr
+++ b/tests/ui/impl-trait/in-trait/signature-mismatch.failure.stderr
@@ -1,5 +1,5 @@
error[E0623]: lifetime mismatch
- --> $DIR/signature-mismatch.rs:56:10
+ --> $DIR/signature-mismatch.rs:77:10
|
LL | &'a self,
| -------- this parameter and the return type are declared with different lifetimes...
diff --git a/tests/ui/impl-trait/in-trait/signature-mismatch.rs b/tests/ui/impl-trait/in-trait/signature-mismatch.rs
index 1d63a6f3ce200..c84a3b8f46b5e 100644
--- a/tests/ui/impl-trait/in-trait/signature-mismatch.rs
+++ b/tests/ui/impl-trait/in-trait/signature-mismatch.rs
@@ -1,4 +1,6 @@
// edition:2021
+// revisions: success failure
+//[success] check-pass
#![feature(return_position_impl_trait_in_trait)]
#![allow(incomplete_features)]
@@ -11,16 +13,25 @@ impl<T> Captures<'_> for T {}
trait Captures2<'a, 'b> {}
impl<T> Captures2<'_, '_> for T {}
-pub trait AsyncTrait {
+trait AsyncTrait {
+ #[cfg(success)]
fn async_fn(&self, buff: &[u8]) -> impl Future<Output = Vec<u8>>;
+
+ #[cfg(success)]
fn async_fn_early<'a: 'a>(&self, buff: &'a [u8]) -> impl Future<Output = Vec<u8>>;
+
+ #[cfg(success)]
fn async_fn_multiple<'a>(&'a self, buff: &[u8])
- -> impl Future<Output = Vec<u8>> + Captures<'a>;
+ -> impl Future<Output = Vec<u8>> + Captures<'a>;
+
+ #[cfg(failure)]
fn async_fn_reduce_outlive<'a, T>(
&'a self,
buff: &[u8],
t: T,
) -> impl Future<Output = Vec<u8>> + 'a;
+
+ #[cfg(success)]
fn async_fn_reduce<'a, T>(
&'a self,
buff: &[u8],
@@ -31,38 +42,49 @@ pub trait AsyncTrait {
pub struct Struct;
impl AsyncTrait for Struct {
+ // Does not capture more lifetimes that trait def'n, since trait def'n
+ // implicitly captures all in-scope lifetimes.
+ #[cfg(success)]
fn async_fn<'a>(&self, buff: &'a [u8]) -> impl Future<Output = Vec<u8>> + 'a {
- //~^ ERROR return type captures more lifetimes than trait definition
async move { buff.to_vec() }
}
+ // Does not capture more lifetimes that trait def'n, since trait def'n
+ // implicitly captures all in-scope lifetimes.
+ #[cfg(success)]
fn async_fn_early<'a: 'a>(&self, buff: &'a [u8]) -> impl Future<Output = Vec<u8>> + 'a {
- //~^ ERROR return type captures more lifetimes than trait definition
async move { buff.to_vec() }
}
+ // Does not capture more lifetimes that trait def'n, since trait def'n
+ // implicitly captures all in-scope lifetimes.
+ #[cfg(success)]
fn async_fn_multiple<'a, 'b>(
&'a self,
buff: &'b [u8],
) -> impl Future<Output = Vec<u8>> + Captures2<'a, 'b> {
- //~^ ERROR return type captures more lifetimes than trait definition
async move { buff.to_vec() }
}
+ // This error message is awkward, but `impl Future<Output = Vec<u8>>`
+ // cannot outlive `'a` (from the trait signature) because it captures
+ // both `T` and `'b`.
+ #[cfg(failure)]
fn async_fn_reduce_outlive<'a, 'b, T>(
&'a self,
buff: &'b [u8],
t: T,
) -> impl Future<Output = Vec<u8>> {
- //~^ ERROR the parameter type `T` may not live long enough
+ //[failure]~^ ERROR lifetime mismatch
async move {
let _t = t;
vec![]
}
}
- // OK: We remove the `Captures<'a>`, providing a guarantee that we don't capture `'a`,
- // but we still fulfill the `Captures<'a>` trait bound.
+ // Does not capture fewer lifetimes that trait def'n (not that it matters),
+ // since impl also captures all in-scope lifetimes.
+ #[cfg(success)]
fn async_fn_reduce<'a, 'b, T>(&'a self, buff: &'b [u8], t: T) -> impl Future<Output = Vec<u8>> {
async move {
let _t = t;
From 690bcc6619aad74d8c32a52c104d4f79fa2f6bf4 Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Tue, 8 Aug 2023 19:59:44 +0000
Subject: [PATCH 3/4] Test variances of opaque captures
---
compiler/rustc_feature/src/builtin_attrs.rs | 1 +
.../rustc_hir_analysis/src/variance/test.rs | 15 +++++++++++
compiler/rustc_span/src/symbol.rs | 1 +
tests/ui/impl-trait/in-trait/variance.rs | 20 ++++++++++++++
tests/ui/impl-trait/in-trait/variance.stderr | 26 +++++++++++++++++++
tests/ui/impl-trait/variance.rs | 16 ++++++++++++
tests/ui/impl-trait/variance.stderr | 26 +++++++++++++++++++
7 files changed, 105 insertions(+)
create mode 100644 tests/ui/impl-trait/in-trait/variance.rs
create mode 100644 tests/ui/impl-trait/in-trait/variance.stderr
create mode 100644 tests/ui/impl-trait/variance.rs
create mode 100644 tests/ui/impl-trait/variance.stderr
diff --git a/compiler/rustc_feature/src/builtin_attrs.rs b/compiler/rustc_feature/src/builtin_attrs.rs
index 168cc16bb367e..e745ef1ec07ed 100644
--- a/compiler/rustc_feature/src/builtin_attrs.rs
+++ b/compiler/rustc_feature/src/builtin_attrs.rs
@@ -813,6 +813,7 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
rustc_attr!(TEST, rustc_insignificant_dtor, Normal, template!(Word), WarnFollowing),
rustc_attr!(TEST, rustc_strict_coherence, Normal, template!(Word), WarnFollowing),
rustc_attr!(TEST, rustc_variance, Normal, template!(Word), WarnFollowing),
+ rustc_attr!(TEST, rustc_variance_of_opaques, Normal, template!(Word), WarnFollowing),
rustc_attr!(TEST, rustc_layout, Normal, template!(List: "field1, field2, ..."), WarnFollowing),
rustc_attr!(TEST, rustc_abi, Normal, template!(List: "field1, field2, ..."), WarnFollowing),
rustc_attr!(TEST, rustc_regions, Normal, template!(Word), WarnFollowing),
diff --git a/compiler/rustc_hir_analysis/src/variance/test.rs b/compiler/rustc_hir_analysis/src/variance/test.rs
index d57d05d7605db..d98dc0e6b83ef 100644
--- a/compiler/rustc_hir_analysis/src/variance/test.rs
+++ b/compiler/rustc_hir_analysis/src/variance/test.rs
@@ -1,9 +1,24 @@
+use rustc_hir::def::DefKind;
+use rustc_hir::def_id::CRATE_DEF_ID;
use rustc_middle::ty::TyCtxt;
use rustc_span::symbol::sym;
use crate::errors;
pub fn test_variance(tcx: TyCtxt<'_>) {
+ if tcx.has_attr(CRATE_DEF_ID, sym::rustc_variance_of_opaques) {
+ for id in tcx.hir().items() {
+ if matches!(tcx.def_kind(id.owner_id), DefKind::OpaqueTy) {
+ let variances_of = tcx.variances_of(id.owner_id);
+
+ tcx.sess.emit_err(errors::VariancesOf {
+ span: tcx.def_span(id.owner_id),
+ variances_of: format!("{variances_of:?}"),
+ });
+ }
+ }
+ }
+
// For unit testing: check for a special "rustc_variance"
// attribute and report an error with various results if found.
for id in tcx.hir().items() {
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index 9d4f49f9453dd..656deebb5d06b 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -1366,6 +1366,7 @@ symbols! {
rustc_trivial_field_reads,
rustc_unsafe_specialization_marker,
rustc_variance,
+ rustc_variance_of_opaques,
rustdoc,
rustdoc_internals,
rustdoc_missing_doc_code_examples,
diff --git a/tests/ui/impl-trait/in-trait/variance.rs b/tests/ui/impl-trait/in-trait/variance.rs
new file mode 100644
index 0000000000000..f8e4ab88c19ae
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/variance.rs
@@ -0,0 +1,20 @@
+#![feature(rustc_attrs, return_position_impl_trait_in_trait)]
+#![allow(internal_features)]
+#![rustc_variance_of_opaques]
+
+trait Captures<'a> {}
+impl<T> Captures<'_> for T {}
+
+trait Foo<'i> {
+ fn implicit_capture_early<'a: 'a>() -> impl Sized {}
+ //~^ [o, *, *, o, o]
+ // Self, 'i, 'a, 'i_duplicated, 'a_duplicated
+
+ fn explicit_capture_early<'a: 'a>() -> impl Sized + Captures<'a> {} //~ [o, *, *, o, o]
+
+ fn implicit_capture_late<'a>(_: &'a ()) -> impl Sized {} //~ [o, *, o, o]
+
+ fn explicit_capture_late<'a>(_: &'a ()) -> impl Sized + Captures<'a> {} //~ [o, *, o, o]
+}
+
+fn main() {}
diff --git a/tests/ui/impl-trait/in-trait/variance.stderr b/tests/ui/impl-trait/in-trait/variance.stderr
new file mode 100644
index 0000000000000..8cae5a92f0dd5
--- /dev/null
+++ b/tests/ui/impl-trait/in-trait/variance.stderr
@@ -0,0 +1,26 @@
+error: [o, *, *, o, o]
+ --> $DIR/variance.rs:9:44
+ |
+LL | fn implicit_capture_early<'a: 'a>() -> impl Sized {}
+ | ^^^^^^^^^^
+
+error: [o, *, *, o, o]
+ --> $DIR/variance.rs:13:44
+ |
+LL | fn explicit_capture_early<'a: 'a>() -> impl Sized + Captures<'a> {}
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: [o, *, o, o]
+ --> $DIR/variance.rs:15:48
+ |
+LL | fn implicit_capture_late<'a>(_: &'a ()) -> impl Sized {}
+ | ^^^^^^^^^^
+
+error: [o, *, o, o]
+ --> $DIR/variance.rs:17:48
+ |
+LL | fn explicit_capture_late<'a>(_: &'a ()) -> impl Sized + Captures<'a> {}
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 4 previous errors
+
diff --git a/tests/ui/impl-trait/variance.rs b/tests/ui/impl-trait/variance.rs
new file mode 100644
index 0000000000000..d6212f8f39372
--- /dev/null
+++ b/tests/ui/impl-trait/variance.rs
@@ -0,0 +1,16 @@
+#![feature(rustc_attrs)]
+#![allow(internal_features)]
+#![rustc_variance_of_opaques]
+
+trait Captures<'a> {}
+impl<T> Captures<'_> for T {}
+
+fn not_captured_early<'a: 'a>() -> impl Sized {} //~ [*]
+
+fn captured_early<'a: 'a>() -> impl Sized + Captures<'a> {} //~ [*, o]
+
+fn not_captured_late<'a>(_: &'a ()) -> impl Sized {} //~ []
+
+fn captured_late<'a>(_: &'a ()) -> impl Sized + Captures<'a> {} //~ [o]
+
+fn main() {}
diff --git a/tests/ui/impl-trait/variance.stderr b/tests/ui/impl-trait/variance.stderr
new file mode 100644
index 0000000000000..6447367541097
--- /dev/null
+++ b/tests/ui/impl-trait/variance.stderr
@@ -0,0 +1,26 @@
+error: [*]
+ --> $DIR/variance.rs:8:36
+ |
+LL | fn not_captured_early<'a: 'a>() -> impl Sized {}
+ | ^^^^^^^^^^
+
+error: [*, o]
+ --> $DIR/variance.rs:10:32
+ |
+LL | fn captured_early<'a: 'a>() -> impl Sized + Captures<'a> {}
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: []
+ --> $DIR/variance.rs:12:40
+ |
+LL | fn not_captured_late<'a>(_: &'a ()) -> impl Sized {}
+ | ^^^^^^^^^^
+
+error: [o]
+ --> $DIR/variance.rs:14:36
+ |
+LL | fn captured_late<'a>(_: &'a ()) -> impl Sized + Captures<'a> {}
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 4 previous errors
+
From f8e0dcbf5627d3e1a70a4d1d6bd1101d5b24f1e3 Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Tue, 8 Aug 2023 20:13:57 +0000
Subject: [PATCH 4/4] Better error message for object type with GAT
---
.../src/traits/select/confirmation.rs | 2 +-
tests/ui/impl-trait/in-trait/object-safety.rs | 2 +-
.../ui/impl-trait/in-trait/object-safety.stderr | 16 +++++++++++-----
3 files changed, 13 insertions(+), 7 deletions(-)
diff --git a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
index 88d0300330917..8a24f96743a6a 100644
--- a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
@@ -548,7 +548,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
obligation.cause.span,
"GATs in trait object shouldn't have been considered",
);
- return Err(SelectionError::Unimplemented);
+ return Err(SelectionError::TraitNotObjectSafe(trait_predicate.trait_ref.def_id));
}
// This maybe belongs in wf, but that can't (doesn't) handle
diff --git a/tests/ui/impl-trait/in-trait/object-safety.rs b/tests/ui/impl-trait/in-trait/object-safety.rs
index 6e02934363d56..9a231e59b09bf 100644
--- a/tests/ui/impl-trait/in-trait/object-safety.rs
+++ b/tests/ui/impl-trait/in-trait/object-safety.rs
@@ -19,5 +19,5 @@ fn main() {
//~| ERROR the trait `Foo` cannot be made into an object
let s = i.baz();
//~^ ERROR the trait `Foo` cannot be made into an object
- //~| ERROR the trait bound `dyn Foo: Foo`
+ //~| ERROR the trait `Foo` cannot be made into an object
}
diff --git a/tests/ui/impl-trait/in-trait/object-safety.stderr b/tests/ui/impl-trait/in-trait/object-safety.stderr
index 1eb063a5fc2e7..0170dc5d0fc85 100644
--- a/tests/ui/impl-trait/in-trait/object-safety.stderr
+++ b/tests/ui/impl-trait/in-trait/object-safety.stderr
@@ -13,13 +13,20 @@ LL | fn baz(&self) -> impl Debug;
| ^^^^^^^^^^ ...because method `baz` references an `impl Trait` type in its return type
= help: consider moving `baz` to another trait
-error[E0277]: the trait bound `dyn Foo: Foo` is not satisfied
+error[E0038]: the trait `Foo` cannot be made into an object
--> $DIR/object-safety.rs:20:15
|
LL | let s = i.baz();
- | ^^^ the trait `Foo` is not implemented for `dyn Foo`
+ | ^^^ `Foo` cannot be made into an object
|
- = help: the trait `Foo` is implemented for `u32`
+note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
+ --> $DIR/object-safety.rs:7:22
+ |
+LL | trait Foo {
+ | --- this trait cannot be made into an object...
+LL | fn baz(&self) -> impl Debug;
+ | ^^^^^^^^^^ ...because method `baz` references an `impl Trait` type in its return type
+ = help: consider moving `baz` to another trait
error[E0038]: the trait `Foo` cannot be made into an object
--> $DIR/object-safety.rs:20:13
@@ -54,5 +61,4 @@ LL | fn baz(&self) -> impl Debug;
error: aborting due to 4 previous errors
-Some errors have detailed explanations: E0038, E0277.
-For more information about an error, try `rustc --explain E0038`.
+For more information about this error, try `rustc --explain E0038`.