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DefineOpaqueTypes::No in UFC Self resolution #121404

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oli-obk opened this issue Feb 21, 2024 · 2 comments · Fixed by #123962
Closed

DefineOpaqueTypes::No in UFC Self resolution #121404

oli-obk opened this issue Feb 21, 2024 · 2 comments · Fixed by #123962
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A-impl-trait Area: `impl Trait`. Universally / existentially quantified anonymous types with static dispatch. C-cleanup Category: PRs that clean code up or issues documenting cleanup.

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@oli-obk
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oli-obk commented Feb 21, 2024

in

rust/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs

Line 1452 in 1d447a9

DefineOpaqueTypes::No,
we disable hidden type registration. I have been unable to craft a test case for this, as either the self_ty arg of instantiate_value_path is None, or there are no generic parameters on the self type, so it gets inference variables which end up working out fine.

As an example:

#![feature(type_alias_impl_trait)]
struct Foo<T>(T);

impl Foo<u32> {
    fn method() {}
    fn method2(self) {}
}

type Bar = impl Sized;

fn bar() -> Bar {
    42_u32
}

impl Foo<Bar> {
    fn foo() -> Bar {
        Self::method();
        //~^ ERROR: no function or associated item named `method` found for struct `Foo<Bar>`
        Foo::<Bar>::method();
        //~^ ERROR: no function or associated item named `method` found for struct `Foo<Bar>`
        let x = Foo(bar());
        Foo::method2(x);
        let x = Self(bar());
        Self::method2(x);
        //~^ ERROR: no function or associated item named `method2` found for struct `Foo<Bar>`
        todo!()
    }
}

fn main() {}

the Foo::method2(x); works fine, none of the others do, and none of them have a self_ty set here either.

Wrapping the types in <> does not have an effect, even if the code seems to hint at that:

rust/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs

Line 1150 in 1d447a9

// `<T>::assoc` will end up here, and so

any ideas @compiler-errors

cc #121394
@oli-obk oli-obk added C-cleanup Category: PRs that clean code up or issues documenting cleanup. A-impl-trait Area: `impl Trait`. Universally / existentially quantified anonymous types with static dispatch. labels Feb 21, 2024
@rustbot rustbot added the needs-triage This issue may need triage. Remove it if it has been sufficiently triaged. label Feb 21, 2024
@compiler-errors
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@oli-obk: This DefineOpaqueTypes::Yes is unreachable until we fix the method (well, associated item) probing in resolve_ty_and_res_fully_qualified_call.

@oli-obk
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oli-obk commented Feb 21, 2024

yay, thought so, I'll add the test with a comment that it is a bug

@Noratrieb Noratrieb removed the needs-triage This issue may need triage. Remove it if it has been sufficiently triaged. label Feb 21, 2024
@oli-obk oli-obk mentioned this issue Apr 15, 2024
Merged
bors added a commit to rust-lang-ci/rust that referenced this issue Apr 15, 2024
@bors
Auto merge of rust-lang#123962 - oli-obk:define_opaque_types5, r=<try>
fe30d25 
change method resolution to constrain hidden types instead of rejecting method candidates

Some of these are in probes and may affect inference. This is therefore a breaking change.

This allows new code to compile on stable:

```rust
trait Trait {}

impl Trait for u32 {}

struct Bar<T>(T);

impl Bar<u32> {
    fn foo(self) {}
}

fn foo(x: bool) -> Bar<impl Sized> {
    if x {
        let x = foo(false);
        x.foo();
        //^ this used to not find the `foo` method, because while we did equate `x`'s type with possible candidates, we didn't allow opaque type inference while doing so
    }
    todo!()
}
```

But it is also a breaking change, since `&self` and `&mut self` method calls on recursive RPIT function calls now constrain the hidden type to `&_` and `&mut _` respectively. This is not what users really expect or want from this, but there's way around this.

r? `@compiler-errors`

fixes  rust-lang#121404

cc rust-lang#116652
@traviscross traviscross mentioned this issue Apr 15, 2024
Open
3 tasks
bors added a commit to rust-lang-ci/rust that referenced this issue Apr 16, 2024
@bors
Auto merge of rust-lang#123962 - oli-obk:define_opaque_types5, r=<try>
035f40f 
change method resolution to constrain hidden types instead of rejecting method candidates

Some of these are in probes and may affect inference. This is therefore a breaking change.

This allows new code to compile on stable:

```rust
trait Trait {}

impl Trait for u32 {}

struct Bar<T>(T);

impl Bar<u32> {
    fn foo(self) {}
}

fn foo(x: bool) -> Bar<impl Sized> {
    if x {
        let x = foo(false);
        x.foo();
        //^ this used to not find the `foo` method, because while we did equate `x`'s type with possible candidates, we didn't allow opaque type inference while doing so
    }
    todo!()
}
```

But it is also a breaking change, since `&self` and `&mut self` method calls on recursive RPIT function calls now constrain the hidden type to `&_` and `&mut _` respectively. This is not what users really expect or want from this, but there's way around this.

r? `@compiler-errors`

fixes  rust-lang#121404

cc rust-lang#116652
bors added a commit to rust-lang-ci/rust that referenced this issue Apr 22, 2024
@bors
Auto merge of rust-lang#123962 - oli-obk:define_opaque_types5, r=<try>
384ba20 
change method resolution to constrain hidden types instead of rejecting method candidates

Some of these are in probes and may affect inference. This is therefore a breaking change.

This allows new code to compile on stable:

```rust
trait Trait {}

impl Trait for u32 {}

struct Bar<T>(T);

impl Bar<u32> {
    fn foo(self) {}
}

fn foo(x: bool) -> Bar<impl Sized> {
    if x {
        let x = foo(false);
        x.foo();
        //^ this used to not find the `foo` method, because while we did equate `x`'s type with possible candidates, we didn't allow opaque type inference while doing so
    }
    todo!()
}
```

But it is also a breaking change, since `&self` and `&mut self` method calls on recursive RPIT function calls now constrain the hidden type to `&_` and `&mut _` respectively. This is not what users really expect or want from this, but there's way around this.

r? `@compiler-errors`

fixes  rust-lang#121404

cc rust-lang#116652
fmease added a commit to fmease/rust that referenced this issue Jun 13, 2024
@fmease
Rollup merge of rust-lang#123962 - oli-obk:define_opaque_types5, r=lcnr
f20fc59 
change method resolution to constrain hidden types instead of rejecting method candidates

Some of these are in probes and may affect inference. This is therefore a breaking change.

This allows new code to compile on stable:

```rust
trait Trait {}

impl Trait for u32 {}

struct Bar<T>(T);

impl Bar<u32> {
    fn foo(self) {}
}

fn foo(x: bool) -> Bar<impl Sized> {
    if x {
        let x = foo(false);
        x.foo();
        //^ this used to not find the `foo` method, because while we did equate `x`'s type with possible candidates, we didn't allow opaque type inference while doing so
    }
    todo!()
}
```

r? `@compiler-errors`

fixes  rust-lang#121404

cc rust-lang#116652
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this issue Jun 13, 2024
@matthiaskrgr
Rollup merge of rust-lang#123962 - oli-obk:define_opaque_types5, r=lcnr
0650026 
change method resolution to constrain hidden types instead of rejecting method candidates

Some of these are in probes and may affect inference. This is therefore a breaking change.

This allows new code to compile on stable:

```rust
trait Trait {}

impl Trait for u32 {}

struct Bar<T>(T);

impl Bar<u32> {
    fn foo(self) {}
}

fn foo(x: bool) -> Bar<impl Sized> {
    if x {
        let x = foo(false);
        x.foo();
        //^ this used to not find the `foo` method, because while we did equate `x`'s type with possible candidates, we didn't allow opaque type inference while doing so
    }
    todo!()
}
```

r? ``@compiler-errors``

fixes  rust-lang#121404

cc rust-lang#116652
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this issue Jun 13, 2024
@matthiaskrgr
Rollup merge of rust-lang#123962 - oli-obk:define_opaque_types5, r=lcnr
9958f8d 
change method resolution to constrain hidden types instead of rejecting method candidates

Some of these are in probes and may affect inference. This is therefore a breaking change.

This allows new code to compile on stable:

```rust
trait Trait {}

impl Trait for u32 {}

struct Bar<T>(T);

impl Bar<u32> {
    fn foo(self) {}
}

fn foo(x: bool) -> Bar<impl Sized> {
    if x {
        let x = foo(false);
        x.foo();
        //^ this used to not find the `foo` method, because while we did equate `x`'s type with possible candidates, we didn't allow opaque type inference while doing so
    }
    todo!()
}
```

r? ```@compiler-errors```

fixes  rust-lang#121404

cc rust-lang#116652
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this issue Jun 13, 2024
@matthiaskrgr
Rollup merge of rust-lang#123962 - oli-obk:define_opaque_types5, r=lcnr
dfd3a49 
change method resolution to constrain hidden types instead of rejecting method candidates

Some of these are in probes and may affect inference. This is therefore a breaking change.

This allows new code to compile on stable:

```rust
trait Trait {}

impl Trait for u32 {}

struct Bar<T>(T);

impl Bar<u32> {
    fn foo(self) {}
}

fn foo(x: bool) -> Bar<impl Sized> {
    if x {
        let x = foo(false);
        x.foo();
        //^ this used to not find the `foo` method, because while we did equate `x`'s type with possible candidates, we didn't allow opaque type inference while doing so
    }
    todo!()
}
```

r? ````@compiler-errors````

fixes  rust-lang#121404

cc rust-lang#116652
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this issue Jun 13, 2024
@matthiaskrgr
Rollup merge of rust-lang#123962 - oli-obk:define_opaque_types5, r=lcnr
3d7a326 
change method resolution to constrain hidden types instead of rejecting method candidates

Some of these are in probes and may affect inference. This is therefore a breaking change.

This allows new code to compile on stable:

```rust
trait Trait {}

impl Trait for u32 {}

struct Bar<T>(T);

impl Bar<u32> {
    fn foo(self) {}
}

fn foo(x: bool) -> Bar<impl Sized> {
    if x {
        let x = foo(false);
        x.foo();
        //^ this used to not find the `foo` method, because while we did equate `x`'s type with possible candidates, we didn't allow opaque type inference while doing so
    }
    todo!()
}
```

r? `````@compiler-errors`````

fixes  rust-lang#121404

cc rust-lang#116652
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this issue Jun 14, 2024
@matthiaskrgr
Rollup merge of rust-lang#123962 - oli-obk:define_opaque_types5, r=lcnr
160b200 
change method resolution to constrain hidden types instead of rejecting method candidates

Some of these are in probes and may affect inference. This is therefore a breaking change.

This allows new code to compile on stable:

```rust
trait Trait {}

impl Trait for u32 {}

struct Bar<T>(T);

impl Bar<u32> {
    fn foo(self) {}
}

fn foo(x: bool) -> Bar<impl Sized> {
    if x {
        let x = foo(false);
        x.foo();
        //^ this used to not find the `foo` method, because while we did equate `x`'s type with possible candidates, we didn't allow opaque type inference while doing so
    }
    todo!()
}
```

r? ``````@compiler-errors``````

fixes  rust-lang#121404

cc rust-lang#116652
@bors bors closed this as completed in 0468462 Jun 14, 2024
rust-timer added a commit to rust-lang-ci/rust that referenced this issue Jun 14, 2024
@rust-timer
Unrolled build for rust-lang#123962
f3aabc3 
Rollup merge of rust-lang#123962 - oli-obk:define_opaque_types5, r=lcnr

change method resolution to constrain hidden types instead of rejecting method candidates

Some of these are in probes and may affect inference. This is therefore a breaking change.

This allows new code to compile on stable:

```rust
trait Trait {}

impl Trait for u32 {}

struct Bar<T>(T);

impl Bar<u32> {
    fn foo(self) {}
}

fn foo(x: bool) -> Bar<impl Sized> {
    if x {
        let x = foo(false);
        x.foo();
        //^ this used to not find the `foo` method, because while we did equate `x`'s type with possible candidates, we didn't allow opaque type inference while doing so
    }
    todo!()
}
```

r? ```````@compiler-errors```````

fixes  rust-lang#121404

cc rust-lang#116652
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