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Auto merge of #129073 - compiler-errors:receiver-variance, r=lcnr
Relate receiver invariantly in method probe for `Mode::Path` Effectively reverts part of #126128 Fixes #126227 This PR changes method probing to use equality for fully path-based method lookup, and subtyping for receiver `.` method lookup. r? lcnr
2 parents 46b0f8b + 05483d5 commit e9e13a6

17 files changed

+141
-56
lines changed

‎compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs

+2-2
Original file line numberDiff line numberDiff line change
@@ -1388,10 +1388,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
13881388
// This also occurs for an enum variant on a type alias.
13891389
let impl_ty = self.normalize(span, tcx.type_of(impl_def_id).instantiate(tcx, args));
13901390
let self_ty = self.normalize(span, self_ty);
1391-
match self.at(&self.misc(span), self.param_env).sub(
1391+
match self.at(&self.misc(span), self.param_env).eq(
13921392
DefineOpaqueTypes::Yes,
1393-
self_ty,
13941393
impl_ty,
1394+
self_ty,
13951395
) {
13961396
Ok(ok) => self.register_infer_ok_obligations(ok),
13971397
Err(_) => {

‎compiler/rustc_hir_typeck/src/method/probe.rs

+22-4
Original file line numberDiff line numberDiff line change
@@ -621,6 +621,16 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
621621
self.unsatisfied_predicates.borrow_mut().clear();
622622
}
623623

624+
/// When we're looking up a method by path (UFCS), we relate the receiver
625+
/// types invariantly. When we are looking up a method by the `.` operator,
626+
/// we relate them covariantly.
627+
fn variance(&self) -> ty::Variance {
628+
match self.mode {
629+
Mode::MethodCall => ty::Covariant,
630+
Mode::Path => ty::Invariant,
631+
}
632+
}
633+
624634
///////////////////////////////////////////////////////////////////////////
625635
// CANDIDATE ASSEMBLY
626636

@@ -1443,7 +1453,8 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
14431453
(xform_self_ty, xform_ret_ty) =
14441454
self.xform_self_ty(probe.item, impl_ty, impl_args);
14451455
xform_self_ty = ocx.normalize(cause, self.param_env, xform_self_ty);
1446-
match ocx.sup(cause, self.param_env, xform_self_ty, self_ty) {
1456+
match ocx.relate(cause, self.param_env, self.variance(), self_ty, xform_self_ty)
1457+
{
14471458
Ok(()) => {}
14481459
Err(err) => {
14491460
debug!("--> cannot relate self-types {:?}", err);
@@ -1514,7 +1525,13 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
15141525
{
15151526
return ProbeResult::NoMatch;
15161527
}
1517-
_ => match ocx.sup(cause, self.param_env, xform_self_ty, self_ty) {
1528+
_ => match ocx.relate(
1529+
cause,
1530+
self.param_env,
1531+
self.variance(),
1532+
self_ty,
1533+
xform_self_ty,
1534+
) {
15181535
Ok(()) => {}
15191536
Err(err) => {
15201537
debug!("--> cannot relate self-types {:?}", err);
@@ -1560,7 +1577,8 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
15601577
(xform_self_ty, xform_ret_ty) =
15611578
self.xform_self_ty(probe.item, trait_ref.self_ty(), trait_ref.args);
15621579
xform_self_ty = ocx.normalize(cause, self.param_env, xform_self_ty);
1563-
match ocx.sup(cause, self.param_env, xform_self_ty, self_ty) {
1580+
match ocx.relate(cause, self.param_env, self.variance(), self_ty, xform_self_ty)
1581+
{
15641582
Ok(()) => {}
15651583
Err(err) => {
15661584
debug!("--> cannot relate self-types {:?}", err);
@@ -1603,7 +1621,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
16031621
}
16041622

16051623
debug!("comparing return_ty {:?} with xform ret ty {:?}", return_ty, xform_ret_ty);
1606-
match ocx.sup(cause, self.param_env, return_ty, xform_ret_ty) {
1624+
match ocx.relate(cause, self.param_env, self.variance(), xform_ret_ty, return_ty) {
16071625
Ok(()) => {}
16081626
Err(_) => {
16091627
result = ProbeResult::BadReturnType;

‎tests/ui/associated-consts/wrong-projection-self-ty-invalid-bivariant-arg.rs

+1
Original file line numberDiff line numberDiff line change
@@ -7,4 +7,5 @@ impl Fail<i32> {
77

88
fn main() {
99
Fail::<()>::C
10+
//~^ ERROR no associated item named `C` found for struct `Fail<()>` in the current scope
1011
}

‎tests/ui/associated-consts/wrong-projection-self-ty-invalid-bivariant-arg.stderr

+15-2
Original file line numberDiff line numberDiff line change
@@ -7,6 +7,19 @@ LL | struct Fail<T>;
77
= help: consider removing `T`, referring to it in a field, or using a marker such as `PhantomData`
88
= help: if you intended `T` to be a const parameter, use `const T: /* Type */` instead
99

10-
error: aborting due to 1 previous error
10+
error[E0599]: no associated item named `C` found for struct `Fail<()>` in the current scope
11+
--> $DIR/wrong-projection-self-ty-invalid-bivariant-arg.rs:9:17
12+
|
13+
LL | struct Fail<T>;
14+
| -------------- associated item `C` not found for this struct
15+
...
16+
LL | Fail::<()>::C
17+
| ^ associated item not found in `Fail<()>`
18+
|
19+
= note: the associated item was found for
20+
- `Fail<i32>`
21+
22+
error: aborting due to 2 previous errors
1123

12-
For more information about this error, try `rustc --explain E0392`.
24+
Some errors have detailed explanations: E0392, E0599.
25+
For more information about an error, try `rustc --explain E0392`.

‎tests/ui/associated-consts/wrong-projection-self-ty-invalid-bivariant-arg2.rs

+1
Original file line numberDiff line numberDiff line change
@@ -14,4 +14,5 @@ impl Fail<i32, i32> {
1414
fn main() {
1515
Fail::<i32, u32>::C
1616
//~^ ERROR: type mismatch
17+
//~| ERROR no associated item named `C` found for struct `Fail<i32, u32>` in the current scope
1718
}

‎tests/ui/associated-consts/wrong-projection-self-ty-invalid-bivariant-arg2.stderr

+15-2
Original file line numberDiff line numberDiff line change
@@ -1,3 +1,15 @@
1+
error[E0599]: no associated item named `C` found for struct `Fail<i32, u32>` in the current scope
2+
--> $DIR/wrong-projection-self-ty-invalid-bivariant-arg2.rs:15:23
3+
|
4+
LL | struct Fail<T: Proj<Assoc = U>, U>(T);
5+
| ---------------------------------- associated item `C` not found for this struct
6+
...
7+
LL | Fail::<i32, u32>::C
8+
| ^ associated item not found in `Fail<i32, u32>`
9+
|
10+
= note: the associated item was found for
11+
- `Fail<i32, i32>`
12+
113
error[E0271]: type mismatch resolving `<i32 as Proj>::Assoc == u32`
214
--> $DIR/wrong-projection-self-ty-invalid-bivariant-arg2.rs:15:5
315
|
@@ -15,6 +27,7 @@ note: required by a bound in `Fail`
1527
LL | struct Fail<T: Proj<Assoc = U>, U>(T);
1628
| ^^^^^^^^^ required by this bound in `Fail`
1729

18-
error: aborting due to 1 previous error
30+
error: aborting due to 2 previous errors
1931

20-
For more information about this error, try `rustc --explain E0271`.
32+
Some errors have detailed explanations: E0271, E0599.
33+
For more information about an error, try `rustc --explain E0271`.

‎tests/ui/coercion/coerce-issue-49593-box-never.fallback.stderr

-11
This file was deleted.

‎tests/ui/coercion/coerce-issue-49593-box-never.rs

+4-4
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
11
//@ revisions: nofallback fallback
2-
//@check-fail
2+
//@[fallback] check-pass
33

44
#![feature(never_type)]
55
#![cfg_attr(fallback, feature(never_type_fallback))]
@@ -13,10 +13,10 @@ fn raw_ptr_box<T>(t: T) -> *mut T {
1313
}
1414

1515
fn foo(x: !) -> Box<dyn Error> {
16-
// Subtyping during method resolution will generate new inference vars and
17-
// subtype them. Thus fallback will not fall back to `!`, but `()` instead.
16+
// Method resolution will generate new inference vars and relate them.
17+
// Thus fallback will not fall back to `!`, but `()` instead.
1818
Box::<_ /* ! */>::new(x)
19-
//~^ ERROR trait bound `(): std::error::Error` is not satisfied
19+
//[nofallback]~^ ERROR trait bound `(): std::error::Error` is not satisfied
2020
}
2121

2222
fn foo_raw_ptr(x: !) -> *mut dyn Error {

‎tests/ui/const-generics/generic_arg_infer/issue-91614.stderr

+2-2
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@ note: required by a const generic parameter in `Mask::<T, N>::splat`
88
--> $SRC_DIR/core/src/../../portable-simd/crates/core_simd/src/masks.rs:LL:COL
99
help: consider giving `y` an explicit type, where the value of const parameter `N` is specified
1010
|
11-
LL | let y: Mask<T, N> = Mask::<_, _>::splat(false);
11+
LL | let y: Mask<_, N> = Mask::<_, _>::splat(false);
1212
| ++++++++++++
1313

1414
error[E0284]: type annotations needed for `Mask<_, _>`
@@ -21,7 +21,7 @@ note: required by a const generic parameter in `Mask`
2121
--> $SRC_DIR/core/src/../../portable-simd/crates/core_simd/src/masks.rs:LL:COL
2222
help: consider giving `y` an explicit type, where the value of const parameter `N` is specified
2323
|
24-
LL | let y: Mask<T, N> = Mask::<_, _>::splat(false);
24+
LL | let y: Mask<_, N> = Mask::<_, _>::splat(false);
2525
| ++++++++++++
2626

2727
error: aborting due to 2 previous errors

‎tests/ui/impl-trait/issues/issue-62742.rs

+2-1
Original file line numberDiff line numberDiff line change
@@ -2,7 +2,8 @@ use std::marker::PhantomData;
22

33
fn a() {
44
WrongImpl::foo(0i32);
5-
//~^ ERROR overflow assigning `_` to `[_]`
5+
//~^ ERROR the function or associated item `foo` exists for struct `SafeImpl<_, RawImpl<_>>`, but its trait bounds were not satisfied
6+
//~| ERROR the trait bound `RawImpl<_>: Raw<_>` is not satisfied
67
}
78

89
fn b() {

‎tests/ui/impl-trait/issues/issue-62742.stderr

+42-10
Original file line numberDiff line numberDiff line change
@@ -1,11 +1,43 @@
1-
error[E0275]: overflow assigning `_` to `[_]`
1+
error[E0599]: the function or associated item `foo` exists for struct `SafeImpl<_, RawImpl<_>>`, but its trait bounds were not satisfied
22
--> $DIR/issue-62742.rs:4:16
33
|
44
LL | WrongImpl::foo(0i32);
5-
| ^^^
5+
| ^^^ function or associated item cannot be called on `SafeImpl<_, RawImpl<_>>` due to unsatisfied trait bounds
6+
...
7+
LL | pub struct RawImpl<T>(PhantomData<T>);
8+
| --------------------- doesn't satisfy `RawImpl<_>: Raw<_>`
9+
...
10+
LL | pub struct SafeImpl<T: ?Sized, A: Raw<T>>(PhantomData<(A, T)>);
11+
| ----------------------------------------- function or associated item `foo` not found for this struct
12+
|
13+
note: trait bound `RawImpl<_>: Raw<_>` was not satisfied
14+
--> $DIR/issue-62742.rs:35:20
15+
|
16+
LL | impl<T: ?Sized, A: Raw<T>> SafeImpl<T, A> {
17+
| ^^^^^^ --------------
18+
| |
19+
| unsatisfied trait bound introduced here
20+
note: the trait `Raw` must be implemented
21+
--> $DIR/issue-62742.rs:19:1
22+
|
23+
LL | pub trait Raw<T: ?Sized> {
24+
| ^^^^^^^^^^^^^^^^^^^^^^^^
25+
26+
error[E0277]: the trait bound `RawImpl<_>: Raw<_>` is not satisfied
27+
--> $DIR/issue-62742.rs:4:5
28+
|
29+
LL | WrongImpl::foo(0i32);
30+
| ^^^^^^^^^ the trait `Raw<_>` is not implemented for `RawImpl<_>`
31+
|
32+
= help: the trait `Raw<[_]>` is implemented for `RawImpl<_>`
33+
note: required by a bound in `SafeImpl`
34+
--> $DIR/issue-62742.rs:33:35
35+
|
36+
LL | pub struct SafeImpl<T: ?Sized, A: Raw<T>>(PhantomData<(A, T)>);
37+
| ^^^^^^ required by this bound in `SafeImpl`
638

739
error[E0599]: the function or associated item `foo` exists for struct `SafeImpl<(), RawImpl<()>>`, but its trait bounds were not satisfied
8-
--> $DIR/issue-62742.rs:9:22
40+
--> $DIR/issue-62742.rs:10:22
941
|
1042
LL | WrongImpl::<()>::foo(0i32);
1143
| ^^^ function or associated item cannot be called on `SafeImpl<(), RawImpl<()>>` due to unsatisfied trait bounds
@@ -17,33 +49,33 @@ LL | pub struct SafeImpl<T: ?Sized, A: Raw<T>>(PhantomData<(A, T)>);
1749
| ----------------------------------------- function or associated item `foo` not found for this struct
1850
|
1951
note: trait bound `RawImpl<()>: Raw<()>` was not satisfied
20-
--> $DIR/issue-62742.rs:34:20
52+
--> $DIR/issue-62742.rs:35:20
2153
|
2254
LL | impl<T: ?Sized, A: Raw<T>> SafeImpl<T, A> {
2355
| ^^^^^^ --------------
2456
| |
2557
| unsatisfied trait bound introduced here
2658
note: the trait `Raw` must be implemented
27-
--> $DIR/issue-62742.rs:18:1
59+
--> $DIR/issue-62742.rs:19:1
2860
|
2961
LL | pub trait Raw<T: ?Sized> {
3062
| ^^^^^^^^^^^^^^^^^^^^^^^^
3163

3264
error[E0277]: the trait bound `RawImpl<()>: Raw<()>` is not satisfied
33-
--> $DIR/issue-62742.rs:9:5
65+
--> $DIR/issue-62742.rs:10:5
3466
|
3567
LL | WrongImpl::<()>::foo(0i32);
3668
| ^^^^^^^^^^^^^^^ the trait `Raw<()>` is not implemented for `RawImpl<()>`
3769
|
3870
= help: the trait `Raw<[()]>` is implemented for `RawImpl<()>`
3971
= help: for that trait implementation, expected `[()]`, found `()`
4072
note: required by a bound in `SafeImpl`
41-
--> $DIR/issue-62742.rs:32:35
73+
--> $DIR/issue-62742.rs:33:35
4274
|
4375
LL | pub struct SafeImpl<T: ?Sized, A: Raw<T>>(PhantomData<(A, T)>);
4476
| ^^^^^^ required by this bound in `SafeImpl`
4577

46-
error: aborting due to 3 previous errors
78+
error: aborting due to 4 previous errors
4779

48-
Some errors have detailed explanations: E0275, E0277, E0599.
49-
For more information about an error, try `rustc --explain E0275`.
80+
Some errors have detailed explanations: E0277, E0599.
81+
For more information about an error, try `rustc --explain E0277`.

‎tests/ui/inference/need_type_info/type-alias-indirect.stderr

+1-1
Original file line numberDiff line numberDiff line change
@@ -2,7 +2,7 @@ error[E0282]: type annotations needed
22
--> $DIR/type-alias-indirect.rs:14:5
33
|
44
LL | IndirectAlias::new();
5-
| ^^^^^^^^^^^^^^^^^^^^ cannot infer type for type parameter `T` declared on the type alias `IndirectAlias`
5+
| ^^^^^^^^^^^^^ cannot infer type for type parameter `T` declared on the type alias `IndirectAlias`
66

77
error: aborting due to 1 previous error
88

‎tests/ui/inference/need_type_info/type-alias.stderr

+3-3
Original file line numberDiff line numberDiff line change
@@ -2,19 +2,19 @@ error[E0282]: type annotations needed
22
--> $DIR/type-alias.rs:12:5
33
|
44
LL | DirectAlias::new()
5-
| ^^^^^^^^^^^^^^^^^^ cannot infer type for type parameter `T` declared on the type alias `DirectAlias`
5+
| ^^^^^^^^^^^^^^^^^^ cannot infer type for type parameter `T`
66

77
error[E0282]: type annotations needed
88
--> $DIR/type-alias.rs:18:5
99
|
1010
LL | IndirectAlias::new();
11-
| ^^^^^^^^^^^^^^^^^^^^ cannot infer type for type parameter `T` declared on the type alias `IndirectAlias`
11+
| ^^^^^^^^^^^^^ cannot infer type for type parameter `T` declared on the type alias `IndirectAlias`
1212

1313
error[E0282]: type annotations needed
1414
--> $DIR/type-alias.rs:32:5
1515
|
1616
LL | DirectButWithDefaultAlias::new();
17-
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot infer type for type parameter `T` declared on the type alias `DirectButWithDefaultAlias`
17+
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot infer type for type parameter `T`
1818

1919
error: aborting due to 3 previous errors
2020

‎tests/ui/methods/receiver-equality.rs

+16
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,16 @@
1+
// Tests that we probe receivers invariantly when using path-based method lookup.
2+
3+
struct B<T>(T);
4+
5+
impl B<fn(&'static ())> {
6+
fn method(self) {
7+
println!("hey");
8+
}
9+
}
10+
11+
fn foo(y: B<fn(&'static ())>) {
12+
B::<for<'a> fn(&'a ())>::method(y);
13+
//~^ ERROR no function or associated item named `method` found
14+
}
15+
16+
fn main() {}

‎tests/ui/methods/receiver-equality.stderr

+12
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,12 @@
1+
error[E0599]: no function or associated item named `method` found for struct `B<for<'a> fn(&'a ())>` in the current scope
2+
--> $DIR/receiver-equality.rs:12:30
3+
|
4+
LL | struct B<T>(T);
5+
| ----------- function or associated item `method` not found for this struct
6+
...
7+
LL | B::<for<'a> fn(&'a ())>::method(y);
8+
| ^^^^^^ function or associated item not found in `B<fn(&())>`
9+
10+
error: aborting due to 1 previous error
11+
12+
For more information about this error, try `rustc --explain E0599`.

‎tests/ui/suggestions/mut-borrow-needed-by-trait.rs

-1
Original file line numberDiff line numberDiff line change
@@ -17,7 +17,6 @@ fn main() {
1717
let fp = BufWriter::new(fp);
1818
//~^ ERROR the trait bound `&dyn std::io::Write: std::io::Write` is not satisfied
1919
//~| ERROR the trait bound `&dyn std::io::Write: std::io::Write` is not satisfied
20-
//~| ERROR the trait bound `&dyn std::io::Write: std::io::Write` is not satisfied
2120

2221
writeln!(fp, "hello world").unwrap(); //~ ERROR the method
2322
}

‎tests/ui/suggestions/mut-borrow-needed-by-trait.stderr

+3-13
Original file line numberDiff line numberDiff line change
@@ -10,16 +10,6 @@ LL | let fp = BufWriter::new(fp);
1010
note: required by a bound in `BufWriter::<W>::new`
1111
--> $SRC_DIR/std/src/io/buffered/bufwriter.rs:LL:COL
1212

13-
error[E0277]: the trait bound `&dyn std::io::Write: std::io::Write` is not satisfied
14-
--> $DIR/mut-borrow-needed-by-trait.rs:17:14
15-
|
16-
LL | let fp = BufWriter::new(fp);
17-
| ^^^^^^^^^ the trait `std::io::Write` is not implemented for `&dyn std::io::Write`
18-
|
19-
= note: `std::io::Write` is implemented for `&mut dyn std::io::Write`, but not for `&dyn std::io::Write`
20-
note: required by a bound in `BufWriter`
21-
--> $SRC_DIR/std/src/io/buffered/bufwriter.rs:LL:COL
22-
2313
error[E0277]: the trait bound `&dyn std::io::Write: std::io::Write` is not satisfied
2414
--> $DIR/mut-borrow-needed-by-trait.rs:17:14
2515
|
@@ -31,21 +21,21 @@ note: required by a bound in `BufWriter`
3121
--> $SRC_DIR/std/src/io/buffered/bufwriter.rs:LL:COL
3222

3323
error[E0599]: the method `write_fmt` exists for struct `BufWriter<&dyn Write>`, but its trait bounds were not satisfied
34-
--> $DIR/mut-borrow-needed-by-trait.rs:22:14
24+
--> $DIR/mut-borrow-needed-by-trait.rs:21:14
3525
|
3626
LL | writeln!(fp, "hello world").unwrap();
3727
| ---------^^---------------- method cannot be called on `BufWriter<&dyn Write>` due to unsatisfied trait bounds
3828
|
3929
note: must implement `io::Write`, `fmt::Write`, or have a `write_fmt` method
40-
--> $DIR/mut-borrow-needed-by-trait.rs:22:14
30+
--> $DIR/mut-borrow-needed-by-trait.rs:21:14
4131
|
4232
LL | writeln!(fp, "hello world").unwrap();
4333
| ^^
4434
= note: the following trait bounds were not satisfied:
4535
`&dyn std::io::Write: std::io::Write`
4636
which is required by `BufWriter<&dyn std::io::Write>: std::io::Write`
4737

48-
error: aborting due to 4 previous errors
38+
error: aborting due to 3 previous errors
4939

5040
Some errors have detailed explanations: E0277, E0599.
5141
For more information about an error, try `rustc --explain E0277`.

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