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derive(SmartPointer): assume pointee from the single generic and better error messages #129467

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merged 1 commit into from
Aug 29, 2024

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dingxiangfei2009
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Fix #129465

Actually RFC says that #[pointee] can be inferred when there is no ambiguity, or there is only one generic type parameter so to say.

cc @Darksonn

r? @compiler-errors

@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Aug 23, 2024
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@rustbot label F-derive_smart_pointer

@rustbot rustbot added the F-derive_coerce_pointee Feature: RFC 3621's oft-renamed implementation label Aug 23, 2024
Comment on lines 86 to 106
if p.attrs().iter().any(|attr| attr.has_name(sym::pointee)) {
if pointee_param.is_some() {
multiple_pointee_diag.push(cx.dcx().struct_span_err(
p.span(),
"`SmartPointer` can only admit one type as pointee",
));
} else {
pointee_param = Some(idx);
match pointee_param {
PointeeChoice::Assumed(_)
| PointeeChoice::Ambiguous
| PointeeChoice::None => {
pointee_param = PointeeChoice::Exactly(idx, p.span())
}
PointeeChoice::Exactly(_, another) => {
pointee_param = PointeeChoice::MultiplePointeeChoice(another, p.span())
}
PointeeChoice::MultiplePointeeChoice(_, _) => {}
}
} else {
match pointee_param {
PointeeChoice::None => pointee_param = PointeeChoice::Assumed(idx),
PointeeChoice::Assumed(_) | PointeeChoice::Ambiguous => {
pointee_param = PointeeChoice::Ambiguous
}
PointeeChoice::Exactly(_, _)
| PointeeChoice::MultiplePointeeChoice(_, _) => {}
}
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I wonder if we can simplify these map operations with side effects by iterating multiple times. For example: (untested)

let self_params = generics
    .params
    .iter()
    .enumerate()
    .map(|(idx, p)| match p.kind {
        GenericParamKind::Lifetime => GenericArg::Lifetime(cx.lifetime(p.span(), p.ident)),
        GenericParamKind::Type { .. } => GenericArg::Type(cx.ty_ident(p.span(), p.ident)),
        GenericParamKind::Const { .. } => GenericArg::Const(cx.const_ident(p.span(), p.ident)),
    })
    .collect::<Vec<_>>();

let all_type_params = generics
    .params
    .iter()
    .enumerate()
    .filter_map(|(idx, p)| match p.kind {
        GenericParamKind::Type { .. } => Some((idx, p.span())),
        _ => None,
    })
    .collect::<Vec<(usize, Span)>>();

let pointee_params = generics
    .params
    .iter()
    .enumerate()
    .filter_map(|(idx, p)| match p.kind {
        GenericParamKind::Type { .. } if p.attrs().iter().any(|attr| attr.has_name(sym::pointee)) => Some((idx, p.span())),
        _ => None,
    })
    .collect::<Vec<(usize, Span)>>();

let pointee_param = match (pointee_params.as_slice(), all_type_params.as_slice()) {
    ([(idx, _span)], _) => idx,
    ([], [(idx, _span)]) => idx,
    ([], []) => {
        cx.dcx().struct_span_err(span, "`SmartPointer` requires a generic parameter").emit();
        return;
    }
    ([], _) => {
        let all_type_spans = all_type_params.into_iter().map(|(idx,span)| span).collect();
        cx.dcx().struct_span_err(all_type_spans, "you must use `#[pointee]` to specify which parameter is the `SmartPointer` pointee").emit();
        return;
    }
    (_, _) => {
        let pointee_spans = pointee_params.into_iter().map(|(idx,span)| span).collect();
        cx.dcx().struct_span_err(pointee_spans, "you can only use `#[pointee]` once").emit();
        return;
    }
};

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Applied with slight adaptation

So now we one pass through the generics to get ourserlves the self_params. One more pass through the iterator is used to collect only the type parameters.

  • If we find zero type parameters, err with diagnosis
  • If we find exactly one type parameter, use it as #[pointee]
  • Otherwise, filter through type parameters on whether there is #[pointee] designation and err when more than one such parameters are found

@dingxiangfei2009 dingxiangfei2009 force-pushed the smart-pointer-relax-pointee branch from bb43160 to ea3a13b Compare August 25, 2024 19:50
(None, _) => {
cx.dcx().struct_span_err(
span,
"Exactly one generic parameters when there are at least two generic type parameters \
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diagnostics should not be capitalized

also this message could be tweaked:

exactly one generic type parameter must be marked as #[pointee] to derive SmartPointer traits

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also, there is no test for this message?

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Oops. Added.

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I forgot to add the hunk with the updated message as per your suggestion. It is checked in now.

}
let pointee_param_idx = if type_params.len() == 1 {
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could you special case the == 0 case?

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Applied. Moved the check above into here.

cx.dcx()
.struct_span_err(
vec![one, another],
"`SmartPointer` can only admit one type as pointee",
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Can you adjust this message?

only one type parameter can be marked as #[pointee] when deriving SmartPointer traits

sounds more natural that way

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Applied

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@rustbot author

@rustbot rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Aug 26, 2024
@dingxiangfei2009 dingxiangfei2009 force-pushed the smart-pointer-relax-pointee branch from ea3a13b to 447ca81 Compare August 28, 2024 17:36
@dingxiangfei2009
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@rustbot ready

  • Ran through the test and made sure that all diagnostic messages appeared, or have been used, at least once
  • Applied suggestions on wording

@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Aug 28, 2024
@dingxiangfei2009 dingxiangfei2009 force-pushed the smart-pointer-relax-pointee branch from 447ca81 to 3914835 Compare August 28, 2024 17:39
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@bors r+ rollup

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bors commented Aug 28, 2024

📌 Commit 3914835 has been approved by compiler-errors

It is now in the queue for this repository.

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Aug 28, 2024
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request Aug 28, 2024
…ax-pointee, r=compiler-errors

derive(SmartPointer): assume pointee from the single generic and better error messages

Fix rust-lang#129465

Actually RFC says that `#[pointee]` can be inferred when there is no ambiguity, or there is only one generic type parameter so to say.

cc `@Darksonn`

r? `@compiler-errors`
bors added a commit to rust-lang-ci/rust that referenced this pull request Aug 28, 2024
…iaskrgr

Rollup of 11 pull requests

Successful merges:

 - rust-lang#128166 (Improved `checked_isqrt` and `isqrt` methods)
 - rust-lang#129170 (Add an ability to convert between `Span` and `visit::Location`)
 - rust-lang#129366 (linker: Synchronize native library search in rustc and linker)
 - rust-lang#129467 (derive(SmartPointer): assume pointee from the single generic and better error messages)
 - rust-lang#129494 (format code in tests/ui/threads-sendsync)
 - rust-lang#129527 (Don't use `TyKind` in a lint)
 - rust-lang#129617 (Update books)
 - rust-lang#129673 (Add fmt::Debug to sync::Weak<T, A>)
 - rust-lang#129683 (copysign with sign being a NaN can have non-portable results)
 - rust-lang#129689 (Move `'tcx` lifetime off of impl and onto methods for `CrateMetadataRef`)
 - rust-lang#129695 (Fix path to run clippy on rustdoc)

r? `@ghost`
`@rustbot` modify labels: rollup
workingjubilee added a commit to workingjubilee/rustc that referenced this pull request Aug 29, 2024
…ax-pointee, r=compiler-errors

derive(SmartPointer): assume pointee from the single generic and better error messages

Fix rust-lang#129465

Actually RFC says that `#[pointee]` can be inferred when there is no ambiguity, or there is only one generic type parameter so to say.

cc ``@Darksonn``

r? ``@compiler-errors``
bors added a commit to rust-lang-ci/rust that referenced this pull request Aug 29, 2024
…kingjubilee

Rollup of 14 pull requests

Successful merges:

 - rust-lang#128192 (rustc_target: Add various aarch64 features)
 - rust-lang#129170 (Add an ability to convert between `Span` and `visit::Location`)
 - rust-lang#129343 (Emit specific message for time<=0.3.35)
 - rust-lang#129378 (Clean up cfg-gating of ProcessPrng extern)
 - rust-lang#129401 (Partially stabilize `feature(new_uninit)`)
 - rust-lang#129467 (derive(SmartPointer): assume pointee from the single generic and better error messages)
 - rust-lang#129494 (format code in tests/ui/threads-sendsync)
 - rust-lang#129617 (Update books)
 - rust-lang#129673 (Add fmt::Debug to sync::Weak<T, A>)
 - rust-lang#129683 (copysign with sign being a NaN can have non-portable results)
 - rust-lang#129689 (Move `'tcx` lifetime off of impl and onto methods for `CrateMetadataRef`)
 - rust-lang#129695 (Fix path to run clippy on rustdoc)
 - rust-lang#129712 (Correct trusty targets to be tier 3)
 - rust-lang#129715 (Update `compiler_builtins` to `0.1.123`)

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit d2418cb into rust-lang:master Aug 29, 2024
6 checks passed
@rustbot rustbot added this to the 1.82.0 milestone Aug 29, 2024
rust-timer added a commit to rust-lang-ci/rust that referenced this pull request Aug 29, 2024
Rollup merge of rust-lang#129467 - dingxiangfei2009:smart-pointer-relax-pointee, r=compiler-errors

derive(SmartPointer): assume pointee from the single generic and better error messages

Fix rust-lang#129465

Actually RFC says that `#[pointee]` can be inferred when there is no ambiguity, or there is only one generic type parameter so to say.

cc ```@Darksonn```

r? ```@compiler-errors```
let mut pointees = type_params
.iter()
.filter_map(|&(idx, span, is_pointee)| is_pointee.then_some((idx, span)))
.fuse();
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Why is this fuse here? type_params is a Vec so there is no way that this iterator could return None and then later return Some.

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The #[pointee] attribute is required even if there is only one generic parameter
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