Tweak E0277 when predicate comes indirectly from ?
When a `?` operation requires an `Into` conversion with additional bounds (like having a concrete error but wanting to convert to a trait object), we handle it speficically and provide the same kind of information we give other `?` related errors. ``` error[E0277]: `?` couldn't convert the error: `E: std::error::Error` is not satisfied --> $DIR/bad-question-mark-on-trait-object.rs:5:13 | LL | fn foo() -> Result<(), Box<dyn std::error::Error>> { | -------------------------------------- required `E: std::error::Error` because of this LL | Ok(bar()?) | ^ the trait `std::error::Error` is not implemented for `E` | = note: the question mark operation (`?`) implicitly performs a conversion on the error value using the `From` trait = note: required for `Box<dyn std::error::Error>` to implement `From<E>` ``` Avoid talking about `FromResidual` when other more relevant information is being given, particularly from `rust_on_unimplemented`.
This commit is contained in:
parent
28b83ee596
commit
e565eeed78
11 changed files with 103 additions and 65 deletions
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@ -192,19 +192,38 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
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let have_alt_message = message.is_some() || label.is_some();
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let is_try_conversion = self.is_try_conversion(span, main_trait_predicate.def_id());
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let is_question_mark = matches!(
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root_obligation.cause.code().peel_derives(),
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ObligationCauseCode::QuestionMark,
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) && !(
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self.tcx.is_diagnostic_item(sym::FromResidual, main_trait_predicate.def_id())
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|| self.tcx.is_lang_item(main_trait_predicate.def_id(), LangItem::Try)
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);
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let is_unsize =
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self.tcx.is_lang_item(leaf_trait_predicate.def_id(), LangItem::Unsize);
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let question_mark_message = "the question mark operation (`?`) implicitly \
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performs a conversion on the error value \
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using the `From` trait";
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let (message, notes, append_const_msg) = if is_try_conversion {
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// We have a `-> Result<_, E1>` and `gives_E2()?`.
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(
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Some(format!(
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"`?` couldn't convert the error to `{}`",
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main_trait_predicate.skip_binder().self_ty(),
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)),
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vec![
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"the question mark operation (`?`) implicitly performs a \
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conversion on the error value using the `From` trait"
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.to_owned(),
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],
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vec![question_mark_message.to_owned()],
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Some(AppendConstMessage::Default),
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)
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} else if is_question_mark {
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// Similar to the case above, but in this case the conversion is for a
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// trait object: `-> Result<_, Box<dyn Error>` and `gives_E()?` when
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// `E: Error` isn't met.
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(
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Some(format!(
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"`?` couldn't convert the error: `{main_trait_predicate}` is \
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not satisfied",
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)),
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vec![question_mark_message.to_owned()],
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Some(AppendConstMessage::Default),
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)
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} else {
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@ -220,8 +239,10 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
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&mut long_ty_file,
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);
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let (err_msg, safe_transmute_explanation) = if self.tcx.is_lang_item(main_trait_predicate.def_id(), LangItem::TransmuteTrait)
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{
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let (err_msg, safe_transmute_explanation) = if self.tcx.is_lang_item(
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main_trait_predicate.def_id(),
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LangItem::TransmuteTrait,
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) {
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// Recompute the safe transmute reason and use that for the error reporting
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match self.get_safe_transmute_error_and_reason(
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obligation.clone(),
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@ -249,18 +270,22 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
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*err.long_ty_path() = long_ty_file;
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let mut suggested = false;
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if is_try_conversion {
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if is_try_conversion || is_question_mark {
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suggested = self.try_conversion_context(&obligation, main_trait_predicate, &mut err);
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}
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if is_try_conversion && let Some(ret_span) = self.return_type_span(&obligation) {
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err.span_label(
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ret_span,
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format!(
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"expected `{}` because of this",
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main_trait_predicate.skip_binder().self_ty()
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),
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);
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if let Some(ret_span) = self.return_type_span(&obligation) {
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if is_try_conversion {
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err.span_label(
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ret_span,
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format!(
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"expected `{}` because of this",
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main_trait_predicate.skip_binder().self_ty()
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),
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);
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} else if is_question_mark {
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err.span_label(ret_span, format!("required `{main_trait_predicate}` because of this"));
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}
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}
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if tcx.is_lang_item(leaf_trait_predicate.def_id(), LangItem::Tuple) {
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@ -302,10 +327,14 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
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// If it has a custom `#[rustc_on_unimplemented]`
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// error message, let's display it as the label!
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err.span_label(span, s);
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if !matches!(leaf_trait_predicate.skip_binder().self_ty().kind(), ty::Param(_)) {
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if !matches!(leaf_trait_predicate.skip_binder().self_ty().kind(), ty::Param(_))
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// When the self type is a type param We don't need to "the trait
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// `std::marker::Sized` is not implemented for `T`" as we will point
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// at the type param with a label to suggest constraining it.
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&& !self.tcx.is_diagnostic_item(sym::FromResidual, leaf_trait_predicate.def_id())
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// Don't say "the trait `FromResidual<Option<Infallible>>` is
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// not implemented for `Result<T, E>`".
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{
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err.help(explanation);
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}
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} else if let Some(custom_explanation) = safe_transmute_explanation {
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@ -2035,6 +2064,11 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
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return false;
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}
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if let &[cand] = &candidates[..] {
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if self.tcx.is_diagnostic_item(sym::FromResidual, cand.def_id)
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&& !self.tcx.features().enabled(sym::try_trait_v2)
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{
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return false;
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}
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let (desc, mention_castable) =
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match (cand.self_ty().kind(), trait_pred.self_ty().skip_binder().kind()) {
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(ty::FnPtr(..), ty::FnDef(..)) => {
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@ -17,8 +17,6 @@ LL | | test()?;
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... |
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LL | | }
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| |_- this function should return `Result` or `Option` to accept `?`
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= help: the trait `FromResidual<_>` is not implemented for `()`
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error: aborting due to 2 previous errors
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@ -6,8 +6,6 @@ LL | async {
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LL | let x: Option<u32> = None;
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LL | x?;
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| ^ cannot use the `?` operator in an async block that returns `{integer}`
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= help: the trait `FromResidual<Option<Infallible>>` is not implemented for `{integer}`
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error[E0277]: the `?` operator can only be used in an async closure that returns `Result` or `Option` (or another type that implements `FromResidual`)
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--> $DIR/try-on-option-in-async.rs:16:10
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@ -20,8 +18,6 @@ LL | | x?;
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LL | | 22_u32
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LL | | };
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| |_____- this function should return `Result` or `Option` to accept `?`
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= help: the trait `FromResidual<Option<Infallible>>` is not implemented for `u32`
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error[E0277]: the `?` operator can only be used in an async function that returns `Result` or `Option` (or another type that implements `FromResidual`)
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--> $DIR/try-on-option-in-async.rs:25:6
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@ -34,8 +30,6 @@ LL | | x?;
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LL | | 22
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LL | | }
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| |_- this function should return `Result` or `Option` to accept `?`
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= help: the trait `FromResidual<Option<Infallible>>` is not implemented for `u32`
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error: aborting due to 3 previous errors
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@ -6,7 +6,6 @@ LL | fn test1() {
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LL | let mut _file = File::create("foo.txt")?;
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| ^ cannot use the `?` operator in a function that returns `()`
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= help: the trait `FromResidual<Result<Infallible, std::io::Error>>` is not implemented for `()`
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help: consider adding return type
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LL ~ fn test1() -> Result<(), Box<dyn std::error::Error>> {
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@ -23,7 +22,6 @@ LL | fn test2() {
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LL | let mut _file = File::create("foo.txt")?;
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| ^ cannot use the `?` operator in a function that returns `()`
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= help: the trait `FromResidual<Result<Infallible, std::io::Error>>` is not implemented for `()`
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help: consider adding return type
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LL ~ fn test2() -> Result<(), Box<dyn std::error::Error>> {
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@ -41,7 +39,6 @@ LL | fn test4(&self) {
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LL | let mut _file = File::create("foo.txt")?;
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| ^ cannot use the `?` operator in a method that returns `()`
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= help: the trait `FromResidual<Result<Infallible, std::io::Error>>` is not implemented for `()`
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help: consider adding return type
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LL ~ fn test4(&self) -> Result<(), Box<dyn std::error::Error>> {
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@ -59,7 +56,6 @@ LL | fn test5(&self) {
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LL | let mut _file = File::create("foo.txt")?;
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| ^ cannot use the `?` operator in a method that returns `()`
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= help: the trait `FromResidual<Result<Infallible, std::io::Error>>` is not implemented for `()`
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help: consider adding return type
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LL ~ fn test5(&self) -> Result<(), Box<dyn std::error::Error>> {
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@ -78,7 +74,6 @@ LL | fn main() {
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LL | let mut _file = File::create("foo.txt")?;
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| ^ cannot use the `?` operator in a function that returns `()`
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= help: the trait `FromResidual<Result<Infallible, std::io::Error>>` is not implemented for `()`
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help: consider adding return type
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LL ~ fn main() -> Result<(), Box<dyn std::error::Error>> {
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LL | mac!();
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| ------ in this macro invocation
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= help: the trait `FromResidual<Result<Infallible, std::io::Error>>` is not implemented for `()`
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= note: this error originates in the macro `mac` (in Nightly builds, run with -Z macro-backtrace for more info)
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help: consider adding return type
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@ -20,9 +20,6 @@ LL | fn option_to_result() -> Result<u64, String> {
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| -------------------------------------------- this function returns a `Result`
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LL | Some(3)?;
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| ^ use `.ok_or(...)?` to provide an error compatible with `Result<u64, String>`
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= help: the trait `FromResidual<Option<Infallible>>` is not implemented for `Result<u64, String>`
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= help: the trait `FromResidual<Result<Infallible, E>>` is implemented for `Result<T, F>`
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error[E0277]: the `?` operator can only be used on `Result`s in a function that returns `Result`
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--> $DIR/bad-interconversion.rs:15:31
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| -------------------------------------------------- this function returns a `Result`
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LL | Ok(ControlFlow::Break(123)?)
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| ^ this `?` produces `ControlFlow<{integer}, Infallible>`, which is incompatible with `Result<u64, String>`
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= help: the trait `FromResidual<ControlFlow<{integer}, Infallible>>` is not implemented for `Result<u64, String>`
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= help: the trait `FromResidual<Result<Infallible, E>>` is implemented for `Result<T, F>`
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error[E0277]: the `?` operator can only be used on `Option`s, not `Result`s, in a function that returns `Option`
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--> $DIR/bad-interconversion.rs:20:22
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| ------------------------------------ this function returns an `Option`
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LL | Some(Err("hello")?)
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| ^ use `.ok()?` if you want to discard the `Result<Infallible, &str>` error information
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|
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= help: the trait `FromResidual<Result<Infallible, &str>>` is not implemented for `Option<u16>`
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= help: the trait `FromResidual<Option<Infallible>>` is implemented for `Option<T>`
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error[E0277]: the `?` operator can only be used on `Option`s in a function that returns `Option`
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--> $DIR/bad-interconversion.rs:25:33
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@ -53,9 +44,6 @@ LL | fn control_flow_to_option() -> Option<u64> {
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| ------------------------------------------ this function returns an `Option`
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LL | Some(ControlFlow::Break(123)?)
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| ^ this `?` produces `ControlFlow<{integer}, Infallible>`, which is incompatible with `Option<u64>`
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|
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= help: the trait `FromResidual<ControlFlow<{integer}, Infallible>>` is not implemented for `Option<u64>`
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= help: the trait `FromResidual<Option<Infallible>>` is implemented for `Option<T>`
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error[E0277]: the `?` operator can only be used on `ControlFlow`s in a function that returns `ControlFlow`
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--> $DIR/bad-interconversion.rs:30:39
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|
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26
tests/ui/try-trait/bad-question-mark-on-trait-object.rs
Normal file
26
tests/ui/try-trait/bad-question-mark-on-trait-object.rs
Normal file
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@ -0,0 +1,26 @@
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struct E;
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struct X;
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fn foo() -> Result<(), Box<dyn std::error::Error>> { //~ NOTE required `E: std::error::Error` because of this
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Ok(bar()?)
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//~^ ERROR `?` couldn't convert the error: `E: std::error::Error` is not satisfied
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//~| NOTE the trait `std::error::Error` is not implemented for `E`
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//~| NOTE the question mark operation (`?`) implicitly performs a conversion on the error value using the `From` trait
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//~| NOTE required for `Box<dyn std::error::Error>` to implement `From<E>`
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//~| NOTE in this expansion
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//~| NOTE in this expansion
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//~| NOTE in this expansion
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}
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fn bat() -> Result<(), X> { //~ NOTE expected `X` because of this
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Ok(bar()?)
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//~^ ERROR `?` couldn't convert the error to `X`
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//~| NOTE the trait `From<E>` is not implemented for `X`
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//~| NOTE this can't be annotated with `?` because it has type `Result<_, E>`
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//~| NOTE the question mark operation (`?`) implicitly performs a conversion on the error value using the `From` trait
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//~| NOTE in this expansion
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//~| NOTE in this expansion
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}
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fn bar() -> Result<(), E> {
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Err(E)
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}
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fn main() {}
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26
tests/ui/try-trait/bad-question-mark-on-trait-object.stderr
Normal file
26
tests/ui/try-trait/bad-question-mark-on-trait-object.stderr
Normal file
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@ -0,0 +1,26 @@
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error[E0277]: `?` couldn't convert the error: `E: std::error::Error` is not satisfied
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--> $DIR/bad-question-mark-on-trait-object.rs:5:13
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|
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LL | fn foo() -> Result<(), Box<dyn std::error::Error>> {
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| -------------------------------------- required `E: std::error::Error` because of this
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LL | Ok(bar()?)
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| ^ the trait `std::error::Error` is not implemented for `E`
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|
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= note: the question mark operation (`?`) implicitly performs a conversion on the error value using the `From` trait
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= note: required for `Box<dyn std::error::Error>` to implement `From<E>`
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error[E0277]: `?` couldn't convert the error to `X`
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--> $DIR/bad-question-mark-on-trait-object.rs:15:13
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|
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LL | fn bat() -> Result<(), X> {
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| ------------- expected `X` because of this
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LL | Ok(bar()?)
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| -----^ the trait `From<E>` is not implemented for `X`
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| |
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| this can't be annotated with `?` because it has type `Result<_, E>`
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|
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= note: the question mark operation (`?`) implicitly performs a conversion on the error value using the `From` trait
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error: aborting due to 2 previous errors
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For more information about this error, try `rustc --explain E0277`.
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@ -6,9 +6,6 @@ LL | fn test_result() -> Result<(),()> {
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LL | let a:Option<()> = Some(());
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LL | a?;
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| ^ use `.ok_or(...)?` to provide an error compatible with `Result<(), ()>`
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|
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= help: the trait `FromResidual<Option<Infallible>>` is not implemented for `Result<(), ()>`
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= help: the trait `FromResidual<Result<Infallible, E>>` is implemented for `Result<T, F>`
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error[E0277]: the `?` operator can only be used on `Option`s, not `Result`s, in a function that returns `Option`
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--> $DIR/option-to-result.rs:11:6
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@ -18,9 +15,6 @@ LL | fn test_option() -> Option<i32>{
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LL | let a:Result<i32, i32> = Ok(5);
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LL | a?;
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| ^ use `.ok()?` if you want to discard the `Result<Infallible, i32>` error information
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|
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= help: the trait `FromResidual<Result<Infallible, i32>>` is not implemented for `Option<i32>`
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= help: the trait `FromResidual<Option<Infallible>>` is implemented for `Option<T>`
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error: aborting due to 2 previous errors
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|
|
|
@ -6,8 +6,6 @@ LL | fn a_function() -> u32 {
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LL | let x: Option<u32> = None;
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LL | x?;
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| ^ cannot use the `?` operator in a function that returns `u32`
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|
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= help: the trait `FromResidual<Option<Infallible>>` is not implemented for `u32`
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error[E0277]: the `?` operator can only be used in a closure that returns `Result` or `Option` (or another type that implements `FromResidual`)
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--> $DIR/try-on-option-diagnostics.rs:14:10
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@ -17,8 +15,6 @@ LL | let a_closure = || {
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LL | let x: Option<u32> = None;
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LL | x?;
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| ^ cannot use the `?` operator in a closure that returns `{integer}`
|
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|
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= help: the trait `FromResidual<Option<Infallible>>` is not implemented for `{integer}`
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error[E0277]: the `?` operator can only be used in a method that returns `Result` or `Option` (or another type that implements `FromResidual`)
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--> $DIR/try-on-option-diagnostics.rs:26:14
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@ -28,8 +24,6 @@ LL | fn a_method() {
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LL | let x: Option<u32> = None;
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LL | x?;
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| ^ cannot use the `?` operator in a method that returns `()`
|
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|
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= help: the trait `FromResidual<Option<Infallible>>` is not implemented for `()`
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error[E0277]: the `?` operator can only be used in a trait method that returns `Result` or `Option` (or another type that implements `FromResidual`)
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--> $DIR/try-on-option-diagnostics.rs:39:14
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@ -39,8 +33,6 @@ LL | fn a_trait_method() {
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LL | let x: Option<u32> = None;
|
||||
LL | x?;
|
||||
| ^ cannot use the `?` operator in a trait method that returns `()`
|
||||
|
|
||||
= help: the trait `FromResidual<Option<Infallible>>` is not implemented for `()`
|
||||
|
||||
error: aborting due to 4 previous errors
|
||||
|
||||
|
|
|
@ -6,9 +6,6 @@ LL | fn foo() -> Result<u32, ()> {
|
|||
LL | let x: Option<u32> = None;
|
||||
LL | x?;
|
||||
| ^ use `.ok_or(...)?` to provide an error compatible with `Result<u32, ()>`
|
||||
|
|
||||
= help: the trait `FromResidual<Option<Infallible>>` is not implemented for `Result<u32, ()>`
|
||||
= help: the trait `FromResidual<Result<Infallible, E>>` is implemented for `Result<T, F>`
|
||||
|
||||
error[E0277]: the `?` operator can only be used in a function that returns `Result` or `Option` (or another type that implements `FromResidual`)
|
||||
--> $DIR/try-on-option.rs:11:6
|
||||
|
@ -18,8 +15,6 @@ LL | fn bar() -> u32 {
|
|||
LL | let x: Option<u32> = None;
|
||||
LL | x?;
|
||||
| ^ cannot use the `?` operator in a function that returns `u32`
|
||||
|
|
||||
= help: the trait `FromResidual<Option<Infallible>>` is not implemented for `u32`
|
||||
|
||||
error: aborting due to 2 previous errors
|
||||
|
||||
|
|
|
@ -7,7 +7,6 @@ LL | // error for a `Try` type on a non-`Try` fn
|
|||
LL | std::fs::File::open("foo")?;
|
||||
| ^ cannot use the `?` operator in a function that returns `()`
|
||||
|
|
||||
= help: the trait `FromResidual<Result<Infallible, std::io::Error>>` is not implemented for `()`
|
||||
help: consider adding return type
|
||||
|
|
||||
LL ~ fn main() -> Result<(), Box<dyn std::error::Error>> {
|
||||
|
@ -33,8 +32,6 @@ LL | fn main() {
|
|||
...
|
||||
LL | ()?;
|
||||
| ^ cannot use the `?` operator in a function that returns `()`
|
||||
|
|
||||
= help: the trait `FromResidual<_>` is not implemented for `()`
|
||||
|
||||
error[E0277]: the trait bound `(): Try` is not satisfied
|
||||
--> $DIR/try-operator-on-main.rs:14:25
|
||||
|
|
Loading…
Add table
Add a link
Reference in a new issue