diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/librustc_trait_selection/traits/error_reporting/mod.rs | 29 | ||||
| -rw-r--r-- | src/test/ui/issues/issue-71036.rs | 17 | ||||
| -rw-r--r-- | src/test/ui/issues/issue-71036.stderr | 12 |
3 files changed, 52 insertions, 6 deletions
diff --git a/src/librustc_trait_selection/traits/error_reporting/mod.rs b/src/librustc_trait_selection/traits/error_reporting/mod.rs index 405c656bad5..784fc36e67e 100644 --- a/src/librustc_trait_selection/traits/error_reporting/mod.rs +++ b/src/librustc_trait_selection/traits/error_reporting/mod.rs @@ -283,6 +283,8 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> { .unwrap_or(false); let is_from = format!("{}", trait_ref.print_only_trait_path()) .starts_with("std::convert::From<"); + let is_unsize = + { Some(trait_ref.def_id()) == self.tcx.lang_items().unsize_trait() }; let (message, note) = if is_try && is_from { ( Some(format!( @@ -405,6 +407,17 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> { return; } + if is_unsize { + // If the obligation failed due to a missing implementation of the + // `Unsize` trait, give a pointer to why that might be the case + err.note( + "all implementations of `Unsize` are provided \ + automatically by the compiler, see \ + <https://doc.rust-lang.org/stable/std/marker/trait.Unsize.html> \ + for more information", + ); + } + // Try to report a help message if !trait_ref.has_infer_types_or_consts() && self.predicate_can_apply(obligation.param_env, trait_ref) @@ -427,12 +440,16 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> { let impl_candidates = self.find_similar_impl_candidates(trait_ref); self.report_similar_impl_candidates(impl_candidates, &mut err); } - self.suggest_change_mut( - &obligation, - &mut err, - &trait_ref, - points_at_arg, - ); + // Changing mutability doesn't make a difference to whether we have + // an `Unsize` impl (Fixes ICE in #71036) + if !is_unsize { + self.suggest_change_mut( + &obligation, + &mut err, + &trait_ref, + points_at_arg, + ); + } } // If this error is due to `!: Trait` not implemented but `(): Trait` is diff --git a/src/test/ui/issues/issue-71036.rs b/src/test/ui/issues/issue-71036.rs new file mode 100644 index 00000000000..01d1cff42e4 --- /dev/null +++ b/src/test/ui/issues/issue-71036.rs @@ -0,0 +1,17 @@ +#![feature(unsize, dispatch_from_dyn)] + +use std::marker::Unsize; +use std::ops::DispatchFromDyn; + +#[allow(unused)] +struct Foo<'a, T: ?Sized> { + _inner: &'a &'a T, +} + +impl<'a, T: ?Sized + Unsize<U>, U: ?Sized> DispatchFromDyn<Foo<'a, U>> for Foo<'a, T> {} +//~^ ERROR the trait bound `&'a T: std::marker::Unsize<&'a U>` is not satisfied +//~| NOTE the trait `std::marker::Unsize<&'a U>` is not implemented for `&'a T` +//~| NOTE all implementations of `Unsize` are provided automatically by the compiler +//~| NOTE required because of the requirements on the impl + +fn main() {} diff --git a/src/test/ui/issues/issue-71036.stderr b/src/test/ui/issues/issue-71036.stderr new file mode 100644 index 00000000000..57cf2468945 --- /dev/null +++ b/src/test/ui/issues/issue-71036.stderr @@ -0,0 +1,12 @@ +error[E0277]: the trait bound `&'a T: std::marker::Unsize<&'a U>` is not satisfied + --> $DIR/issue-71036.rs:11:1 + | +LL | impl<'a, T: ?Sized + Unsize<U>, U: ?Sized> DispatchFromDyn<Foo<'a, U>> for Foo<'a, T> {} + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `std::marker::Unsize<&'a U>` is not implemented for `&'a T` + | + = note: all implementations of `Unsize` are provided automatically by the compiler, see <https://doc.rust-lang.org/stable/std/marker/trait.Unsize.html> for more information + = note: required because of the requirements on the impl of `std::ops::DispatchFromDyn<&'a &'a U>` for `&'a &'a T` + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0277`. |