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Auto merge of #45772 - leodasvacas:fix-auto-bounds-in-trait-objects, r=nikomatsakis
Fix checking of auto trait bounds in trait objects. Any auto trait is allowed in trait object bounds. Fix duplicate check of type and lifetime parameter count, which we were [emitting twice](https://play.rust-lang.org/?gist=37dbbdbbec62dec423bb8f6d92f137cc&version=stable). Note: This was the last use of `Send` in the compiler, meaning after a new `stage0` we could remove the `send` lang item.
2 parents c703ff2 + 7995f87 commit e528c7e

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+17
-32
lines changed

9 files changed

+17
-32
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‎src/libcore/marker.rs

+1-1
Original file line numberDiff line numberDiff line change
@@ -39,7 +39,7 @@ use hash::Hasher;
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/// [arc]: ../../std/sync/struct.Arc.html
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/// [ub]: ../../reference/behavior-considered-undefined.html
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#[stable(feature = "rust1", since = "1.0.0")]
42-
#[lang = "send"]
42+
#[cfg_attr(stage0, lang = "send")]
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#[rustc_on_unimplemented = "`{Self}` cannot be sent between threads safely"]
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pub unsafe trait Send {
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// empty.

‎src/librustc/middle/lang_items.rs

-1
Original file line numberDiff line numberDiff line change
@@ -229,7 +229,6 @@ language_item_table! {
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F32ImplItem, "f32", f32_impl;
230230
F64ImplItem, "f64", f64_impl;
231231

232-
SendTraitLangItem, "send", send_trait;
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SizedTraitLangItem, "sized", sized_trait;
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UnsizeTraitLangItem, "unsize", unsize_trait;
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CopyTraitLangItem, "copy", copy_trait;

‎src/librustc_typeck/astconv.rs

+5-22
Original file line numberDiff line numberDiff line change
@@ -572,8 +572,8 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
572572
let b = &trait_bounds[0];
573573
let span = b.trait_ref.path.span;
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struct_span_err!(self.tcx().sess, span, E0225,
575-
"only Send/Sync traits can be used as additional traits in a trait object")
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.span_label(span, "non-Send/Sync additional trait")
575+
"only auto traits can be used as additional traits in a trait object")
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.span_label(span, "non-auto additional trait")
577577
.emit();
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}
579579

@@ -1257,27 +1257,10 @@ fn split_auto_traits<'a, 'b, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
12571257
-> (Vec<DefId>, Vec<&'b hir::PolyTraitRef>)
12581258
{
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let (auto_traits, trait_bounds): (Vec<_>, _) = trait_bounds.iter().partition(|bound| {
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// Checks whether `trait_did` is an auto trait and adds it to `auto_traits` if so.
12601261
match bound.trait_ref.path.def {
1261-
Def::Trait(trait_did) => {
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// Checks whether `trait_did` refers to one of the builtin
1263-
// traits, like `Send`, and adds it to `auto_traits` if so.
1264-
if Some(trait_did) == tcx.lang_items().send_trait() ||
1265-
Some(trait_did) == tcx.lang_items().sync_trait() {
1266-
let segments = &bound.trait_ref.path.segments;
1267-
segments[segments.len() - 1].with_parameters(|parameters| {
1268-
if !parameters.types.is_empty() {
1269-
check_type_argument_count(tcx, bound.trait_ref.path.span,
1270-
parameters.types.len(), &[]);
1271-
}
1272-
if !parameters.lifetimes.is_empty() {
1273-
report_lifetime_number_error(tcx, bound.trait_ref.path.span,
1274-
parameters.lifetimes.len(), 0);
1275-
}
1276-
});
1277-
true
1278-
} else {
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false
1280-
}
1262+
Def::Trait(trait_did) if tcx.trait_is_auto(trait_did) => {
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true
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}
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_ => false
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}

‎src/librustc_typeck/diagnostics.rs

+3-3
Original file line numberDiff line numberDiff line change
@@ -2455,9 +2455,9 @@ fn main() {
24552455
}
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```
24572457
2458-
Send and Sync are an exception to this rule: it's possible to have bounds of
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one non-builtin trait, plus either or both of Send and Sync. For example, the
2460-
following compiles correctly:
2458+
Auto traits such as Send and Sync are an exception to this rule:
2459+
It's possible to have bounds of one non-builtin trait, plus any number of
2460+
auto traits. For example, the following compiles correctly:
24612461
24622462
```
24632463
fn main() {

‎src/test/compile-fail/E0225.rs

+2-2
Original file line numberDiff line numberDiff line change
@@ -10,6 +10,6 @@
1010

1111
fn main() {
1212
let _: Box<std::io::Read + std::io::Write>;
13-
//~^ ERROR only Send/Sync traits can be used as additional traits in a trait object [E0225]
14-
//~| NOTE non-Send/Sync additional trait
13+
//~^ ERROR only auto traits can be used as additional traits in a trait object [E0225]
14+
//~| NOTE non-auto additional trait
1515
}

‎src/test/compile-fail/bad-sized.rs

+1-1
Original file line numberDiff line numberDiff line change
@@ -12,7 +12,7 @@ trait Trait {}
1212

1313
pub fn main() {
1414
let x: Vec<Trait + Sized> = Vec::new();
15-
//~^ ERROR only Send/Sync traits can be used as additional traits in a trait object
15+
//~^ ERROR only auto traits can be used as additional traits in a trait object
1616
//~| ERROR the trait bound `Trait: std::marker::Sized` is not satisfied
1717
//~| ERROR the trait bound `Trait: std::marker::Sized` is not satisfied
1818
}

‎src/test/compile-fail/issue-22560.rs

+1-1
Original file line numberDiff line numberDiff line change
@@ -23,6 +23,6 @@ type Test = Add +
2323
//~| NOTE missing reference to `RHS`
2424
//~| NOTE because of the default `Self` reference, type parameters must be specified on object types
2525
//~| ERROR E0225
26-
//~| NOTE non-Send/Sync additional trait
26+
//~| NOTE non-auto additional trait
2727

2828
fn main() { }

‎src/test/compile-fail/issue-32963.rs

+1-1
Original file line numberDiff line numberDiff line change
@@ -16,6 +16,6 @@ fn size_of_copy<T: Copy+?Sized>() -> usize { mem::size_of::<T>() }
1616

1717
fn main() {
1818
size_of_copy::<Misc+Copy>();
19-
//~^ ERROR only Send/Sync traits can be used as additional traits in a trait object
19+
//~^ ERROR only auto traits can be used as additional traits in a trait object
2020
//~| ERROR the trait bound `Misc: std::marker::Copy` is not satisfied
2121
}

‎src/test/run-pass/auto-traits.rs

+3
Original file line numberDiff line numberDiff line change
@@ -33,4 +33,7 @@ fn main() {
3333
take_auto(AutoBool(true));
3434
take_auto_unsafe(0);
3535
take_auto_unsafe(AutoBool(true));
36+
37+
/// Auto traits are allowed in trait object bounds.
38+
let _: &(Send + Auto) = &0;
3639
}

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