From 6c0a591deef190ab9bf12836467079367a366c35 Mon Sep 17 00:00:00 2001 From: Michael Goulet Date: Sun, 19 Jun 2022 20:49:07 -0700 Subject: [PATCH] Fix trait object reborrow suggestion --- compiler/rustc_middle/src/traits/mod.rs | 2 +- .../src/traits/error_reporting/mod.rs | 7 +++---- .../src/traits/error_reporting/suggestions.rs | 2 +- .../src/traits/select/confirmation.rs | 6 +++--- .../suggest-borrow-to-dyn-object.rs | 16 ++++++++++++++++ .../suggest-borrow-to-dyn-object.stderr | 19 +++++++++++++++++++ 6 files changed, 43 insertions(+), 9 deletions(-) create mode 100644 src/test/ui/suggestions/suggest-borrow-to-dyn-object.rs create mode 100644 src/test/ui/suggestions/suggest-borrow-to-dyn-object.stderr diff --git a/compiler/rustc_middle/src/traits/mod.rs b/compiler/rustc_middle/src/traits/mod.rs index ed8de24a65eef..7f913faf86058 100644 --- a/compiler/rustc_middle/src/traits/mod.rs +++ b/compiler/rustc_middle/src/traits/mod.rs @@ -253,7 +253,7 @@ pub enum ObligationCauseCode<'tcx> { ObjectTypeBound(Ty<'tcx>, ty::Region<'tcx>), /// Obligation incurred due to an object cast. - ObjectCastObligation(/* Object type */ Ty<'tcx>), + ObjectCastObligation(/* Concrete type */ Ty<'tcx>, /* Object type */ Ty<'tcx>), /// Obligation incurred due to a coercion. Coercion { diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs index af0803fbd5414..debb9e8295122 100644 --- a/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs +++ b/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs @@ -484,10 +484,9 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> { err.span_label(span, explanation); } - if let ObligationCauseCode::ObjectCastObligation(obj_ty) = obligation.cause.code().peel_derives() && - let Some(self_ty) = trait_predicate.self_ty().no_bound_vars() && + if let ObligationCauseCode::ObjectCastObligation(concrete_ty, obj_ty) = obligation.cause.code().peel_derives() && Some(trait_ref.def_id()) == self.tcx.lang_items().sized_trait() { - self.suggest_borrowing_for_object_cast(&mut err, &obligation, self_ty, *obj_ty); + self.suggest_borrowing_for_object_cast(&mut err, &root_obligation, *concrete_ty, *obj_ty); } if trait_predicate.is_const_if_const() && obligation.param_env.is_const() { @@ -1560,7 +1559,7 @@ impl<'a, 'tcx> InferCtxtPrivExt<'a, 'tcx> for InferCtxt<'a, 'tcx> { obligation.cause.code().peel_derives(), ObligationCauseCode::ItemObligation(_) | ObligationCauseCode::BindingObligation(_, _) - | ObligationCauseCode::ObjectCastObligation(_) + | ObligationCauseCode::ObjectCastObligation(..) | ObligationCauseCode::OpaqueType ); if let Err(error) = self.at(&obligation.cause, obligation.param_env).eq_exp( diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs index fbe66d7dcdd2b..166c7a4110b6c 100644 --- a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs +++ b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs @@ -2217,7 +2217,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> { err.span_note(tcx.def_span(item_def_id), &descr); } } - ObligationCauseCode::ObjectCastObligation(object_ty) => { + ObligationCauseCode::ObjectCastObligation(_, object_ty) => { err.note(&format!( "required for the cast to the object type `{}`", self.ty_to_string(object_ty) diff --git a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs index 5942bb79d69e8..e1131140c39e8 100644 --- a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs +++ b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs @@ -813,7 +813,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> { let cause = ObligationCause::new( obligation.cause.span, obligation.cause.body_id, - ObjectCastObligation(target), + ObjectCastObligation(source, target), ); let outlives = ty::OutlivesPredicate(r_a, r_b); nested.push(Obligation::with_depth( @@ -910,7 +910,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> { let cause = ObligationCause::new( obligation.cause.span, obligation.cause.body_id, - ObjectCastObligation(target), + ObjectCastObligation(source, target), ); let outlives = ty::OutlivesPredicate(r_a, r_b); nested.push(Obligation::with_depth( @@ -931,7 +931,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> { let cause = ObligationCause::new( obligation.cause.span, obligation.cause.body_id, - ObjectCastObligation(target), + ObjectCastObligation(source, target), ); let predicate_to_obligation = |predicate| { diff --git a/src/test/ui/suggestions/suggest-borrow-to-dyn-object.rs b/src/test/ui/suggestions/suggest-borrow-to-dyn-object.rs new file mode 100644 index 0000000000000..120fc538307a7 --- /dev/null +++ b/src/test/ui/suggestions/suggest-borrow-to-dyn-object.rs @@ -0,0 +1,16 @@ +use std::ffi::{OsStr, OsString}; +use std::path::Path; + +fn check(p: &dyn AsRef) { + let m = std::fs::metadata(&p); + println!("{:?}", &m); +} + +fn main() { + let s: OsString = ".".into(); + let s: &OsStr = &s; + check(s); + //~^ ERROR the size for values of type `[u8]` cannot be known at compilation time + //~| HELP within `OsStr`, the trait `Sized` is not implemented for `[u8]` + //~| HELP consider borrowing the value, since `&OsStr` can be coerced into `dyn AsRef` +} diff --git a/src/test/ui/suggestions/suggest-borrow-to-dyn-object.stderr b/src/test/ui/suggestions/suggest-borrow-to-dyn-object.stderr new file mode 100644 index 0000000000000..8961f4275a283 --- /dev/null +++ b/src/test/ui/suggestions/suggest-borrow-to-dyn-object.stderr @@ -0,0 +1,19 @@ +error[E0277]: the size for values of type `[u8]` cannot be known at compilation time + --> $DIR/suggest-borrow-to-dyn-object.rs:12:11 + | +LL | check(s); + | ----- ^ doesn't have a size known at compile-time + | | + | required by a bound introduced by this call + | + = help: within `OsStr`, the trait `Sized` is not implemented for `[u8]` + = note: required because it appears within the type `OsStr` + = note: required for the cast to the object type `dyn AsRef` +help: consider borrowing the value, since `&OsStr` can be coerced into `dyn AsRef` + | +LL | check(&s); + | + + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0277`.