Suggest creating unary tuples when types don't match a trait #132583
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r? @nnethercote rustbot has assigned @nnethercote. Use |
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| LL | check(((),)); | ||
| | + ++ |
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Is this suggestion okay? I'm not quite sure what #[do_not_recommend] is supposed to (not) show. Its rfc only talks about not mentioning confusing traits.
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| self.infcx.enter_forall(trait_ref, |trait_ref| { | ||
| if self | ||
| .type_implements_trait(trait_ref.def_id, trait_ref.args, root_obligation.param_env) | ||
| .must_apply_modulo_regions() | ||
| { | ||
| err.multipart_suggestion_verbose( | ||
| format!("use a unary tuple instead"), | ||
| vec![(span.shrink_to_lo(), "(".into()), (span.shrink_to_hi(), ",)".into())], | ||
| Applicability::MaybeIncorrect, | ||
| ); | ||
| } | ||
| }); | ||
| } |
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this is kinda unnecessary. instead of using enter_forall and calling type_implements_trait, just use predicate_must_hold_modulo_regions.
| obligation: &PredicateObligation<'tcx>, | ||
| span: Span, | ||
| ) { | ||
| if !matches!(obligation.cause.code(), ObligationCauseCode::FunctionArg { .. }) { |
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I would turn this into an if let ObligationCauseCode::FunctionArg { arg_hir_id, .. } = ....
Then use the span from arg_hir_id via tcx.hir.span(arg_hir_id). It may seem roundabout, but there's always a chance that the obligation span has been messed with, and getting the span from the actual arg expression is strictly more right...
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@bors r+ rollup |
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…iaskrgr Rollup of 6 pull requests Successful merges: - rust-lang#132355 (Fix compiler panic with a large number of threads) - rust-lang#132486 (No need to instantiate binder in `confirm_async_closure_candidate`) - rust-lang#132544 (Use backticks instead of single quotes for library feature names in diagnostics) - rust-lang#132559 (find the generic container rather than simply looking up for the assoc with const arg) - rust-lang#132579 (add rustc std workspace crate sources) - rust-lang#132583 (Suggest creating unary tuples when types don't match a trait) r? `@ghost` `@rustbot` modify labels: rollup
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Rollup merge of rust-lang#132583 - mejrs:tuples, r=compiler-errors Suggest creating unary tuples when types don't match a trait When you want to have a variadic function, a common workaround to implement this is to create a trait and then implement that trait for various tuples. For example in `pyo3` there exists ```rust /// Calls the object with only positional arguments. pub fn call1(&self, args: impl IntoPy<Py<PyTuple>>) -> PyResult<&PyAny> { ... } ``` with various impls like ```rust impl<A: IntoPy<PyObject> IntoPy<Py<PyAny>> for (A,) impl<A: IntoPy<PyObject, B: IntoPy<PyObject> IntoPy<Py<PyAny>> for (A, B) ... etc ``` This means that if you want to call the method with a single item you have to create a unary tuple, like `(x,)`, rather than just `x`. This PR implements a suggestion to do that, if applicable.
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When you want to have a variadic function, a common workaround to implement this is to create a trait and then implement that trait for various tuples. For example in
pyo3there existswith various impls like
This means that if you want to call the method with a single item you have to create a unary tuple, like
(x,), rather than justx.This PR implements a suggestion to do that, if applicable.