Suggest .as_ref() when appropriate for Option and Result
This commit is contained in:
Esteban Küber
parent
fb86d604bf
commit
8da6727e96
4 changed files with 165 additions and 47 deletions
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@ -956,6 +956,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
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diag.span_label(span, message);
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}
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}
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self.suggest_as_ref_where_appropriate(span, &exp_found, diag);
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}
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diag.note_expected_found(&"type", expected, found);
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@ -972,6 +973,79 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
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self.note_error_origin(diag, &cause);
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}
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/// When encountering a case where `.as_ref()` on a `Result` or `Option` would be appropriate,
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/// suggest it.
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fn suggest_as_ref_where_appropriate(
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&self,
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span: Span,
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exp_found: &ty::error::ExpectedFound<Ty<'tcx>>,
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diag: &mut DiagnosticBuilder<'tcx>,
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) {
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match (&exp_found.expected.sty, &exp_found.found.sty) {
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(TyKind::Adt(exp_def, exp_substs), TyKind::Ref(_, found_ty, _)) => {
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if let TyKind::Adt(found_def, found_substs) = found_ty.sty {
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let path_str = format!("{:?}", exp_def);
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if exp_def == &found_def {
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let opt_msg = "you can convert from `&Option<T>` to `Option<&T>` using \
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`.as_ref()`";
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let result_msg = "you can convert from `&Result<T, E>` to \
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`Result<&T, &E>` using `.as_ref()`";
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let have_as_ref = &[
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("std::option::Option", opt_msg),
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("core::option::Option", opt_msg),
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("std::result::Result", result_msg),
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("core::result::Result", result_msg),
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];
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if let Some(msg) = have_as_ref.iter()
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.filter_map(|(path, msg)| if &path_str == path {
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Some(msg)
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} else {
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None
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}).next()
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{
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let mut show_suggestion = true;
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for (exp_ty, found_ty) in exp_substs.types().zip(found_substs.types()) {
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if let TyKind::Ref(_, exp_ty, _) = exp_ty.sty {
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match (&exp_ty.sty, &found_ty.sty) {
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(TyKind::Adt(exp_did, _), TyKind::Adt(found_did, _))
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if exp_did == found_did => {}
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(TyKind::Bool, TyKind::Bool) |
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(TyKind::Char, TyKind::Char) |
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(TyKind::Str, TyKind::Str) |
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(_, TyKind::Param(_)) |
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(_, TyKind::Infer(_)) |
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(TyKind::Param(_), _) |
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(TyKind::Infer(_), _) => {}
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(TyKind::Int(x), TyKind::Int(y)) if x == y => {}
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(TyKind::Uint(x), TyKind::Uint(y)) if x == y => {}
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(TyKind::Int(x), TyKind::Int(y)) if x == y => {}
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(TyKind::Uint(x), TyKind::Uint(y)) if x == y => {}
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(TyKind::Float(x), TyKind::Float(y)) if x == y => {}
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_ => show_suggestion = false,
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}
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} else {
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show_suggestion = false;
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}
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}
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if let (Ok(snippet), true) = (
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self.tcx.sess.source_map().span_to_snippet(span),
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show_suggestion,
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) {
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diag.span_suggestion_with_applicability(
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span,
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msg,
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format!("{}.as_ref()", snippet),
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Applicability::MachineApplicable,
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);
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}
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}
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}
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}
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}
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_ => {}
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}
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}
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pub fn report_and_explain_type_error(
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&self,
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trace: TypeTrace<'tcx>,
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@ -1,47 +0,0 @@
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error[E0308]: mismatched types
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--> $DIR/as-ref.rs:6:27
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LL | opt.map(|arg| takes_ref(arg));
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| - ^^^ expected &Foo, found struct `Foo`
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| |
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| help: consider using `as_ref` instead: `as_ref().`
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= note: expected type `&Foo`
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found type `Foo`
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error[E0308]: mismatched types
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--> $DIR/as-ref.rs:8:37
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LL | opt.and_then(|arg| Some(takes_ref(arg)));
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| - ^^^ expected &Foo, found struct `Foo`
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| |
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| help: consider using `as_ref` instead: `as_ref().`
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= note: expected type `&Foo`
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found type `Foo`
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error[E0308]: mismatched types
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--> $DIR/as-ref.rs:11:27
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LL | opt.map(|arg| takes_ref(arg));
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| - ^^^ expected &Foo, found struct `Foo`
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| |
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| help: consider using `as_ref` instead: `as_ref().`
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= note: expected type `&Foo`
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found type `Foo`
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error[E0308]: mismatched types
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--> $DIR/as-ref.rs:13:35
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LL | opt.and_then(|arg| Ok(takes_ref(arg)));
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| - ^^^ expected &Foo, found struct `Foo`
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| |
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| help: consider using `as_ref` instead: `as_ref().`
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= note: expected type `&Foo`
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found type `Foo`
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error: aborting due to 4 previous errors
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For more information about this error, try `rustc --explain E0308`.
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@ -12,4 +12,14 @@ fn main() {
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//~^ ERROR mismatched types [E0308]
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opt.and_then(|arg| Ok(takes_ref(arg)));
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//~^ ERROR mismatched types [E0308]
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let x: &Option<usize> = &Some(3);
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let y: Option<&usize> = x;
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//~^ ERROR mismatched types [E0308]
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let x: &Result<usize, usize> = &Ok(3);
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let y: Result<&usize, &usize> = x;
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//~^ ERROR mismatched types [E0308]
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// note: do not suggest because of `E: usize`
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let x: &Result<usize, usize> = &Ok(3);
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let y: Result<&usize, usize> = x;
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//~^ ERROR mismatched types [E0308]
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}
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81
src/test/ui/suggestions/as-ref.stderr
Normal file
81
src/test/ui/suggestions/as-ref.stderr
Normal file
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@ -0,0 +1,81 @@
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error[E0308]: mismatched types
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--> $DIR/as-ref.rs:6:27
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LL | opt.map(|arg| takes_ref(arg));
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| - ^^^ expected &Foo, found struct `Foo`
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| |
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| help: consider using `as_ref` instead: `as_ref().`
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= note: expected type `&Foo`
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found type `Foo`
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error[E0308]: mismatched types
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--> $DIR/as-ref.rs:8:37
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LL | opt.and_then(|arg| Some(takes_ref(arg)));
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| - ^^^ expected &Foo, found struct `Foo`
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| |
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| help: consider using `as_ref` instead: `as_ref().`
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= note: expected type `&Foo`
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found type `Foo`
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error[E0308]: mismatched types
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--> $DIR/as-ref.rs:11:27
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LL | opt.map(|arg| takes_ref(arg));
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| - ^^^ expected &Foo, found struct `Foo`
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| |
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| help: consider using `as_ref` instead: `as_ref().`
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= note: expected type `&Foo`
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found type `Foo`
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error[E0308]: mismatched types
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--> $DIR/as-ref.rs:13:35
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LL | opt.and_then(|arg| Ok(takes_ref(arg)));
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| - ^^^ expected &Foo, found struct `Foo`
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| |
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| help: consider using `as_ref` instead: `as_ref().`
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= note: expected type `&Foo`
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found type `Foo`
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error[E0308]: mismatched types
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--> $DIR/as-ref.rs:16:27
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LL | let y: Option<&usize> = x;
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| ^
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| |
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| expected enum `std::option::Option`, found reference
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| help: you can convert from `&Option<T>` to `Option<&T>` using `.as_ref()`: `x.as_ref()`
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= note: expected type `std::option::Option<&usize>`
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found type `&std::option::Option<usize>`
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error[E0308]: mismatched types
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--> $DIR/as-ref.rs:19:35
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LL | let y: Result<&usize, &usize> = x;
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| ^ expected enum `std::result::Result`, found reference
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= note: expected type `std::result::Result<&usize, &usize>`
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found type `&std::result::Result<usize, usize>`
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help: you can convert from `&Result<T, E>` to `Result<&T, &E>` using `.as_ref()`
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LL | let y: Result<&usize, &usize> = x.as_ref();
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| ^^^^^^^^^^
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error[E0308]: mismatched types
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--> $DIR/as-ref.rs:23:34
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LL | let y: Result<&usize, usize> = x;
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| ^ expected enum `std::result::Result`, found reference
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= note: expected type `std::result::Result<&usize, usize>`
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found type `&std::result::Result<usize, usize>`
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error: aborting due to 7 previous errors
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For more information about this error, try `rustc --explain E0308`.
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