diff --git a/src/librustc_trait_selection/traits/error_reporting/mod.rs b/src/librustc_trait_selection/traits/error_reporting/mod.rs index 2aef8aaf0e303..b1c6815c7414f 100644 --- a/src/librustc_trait_selection/traits/error_reporting/mod.rs +++ b/src/librustc_trait_selection/traits/error_reporting/mod.rs @@ -1000,12 +1000,15 @@ trait InferCtxtPrivExt<'tcx> { trait_ref: &ty::PolyTraitRef<'tcx>, ); - fn mk_obligation_for_def_id( + /// Creates a `PredicateObligation` with `new_self_ty` replacing the existing type in the + /// `trait_ref`. + /// + /// For this to work, `new_self_ty` must have no escaping bound variables. + fn mk_trait_obligation_with_new_self_ty( &self, - def_id: DefId, - output_ty: Ty<'tcx>, - cause: ObligationCause<'tcx>, param_env: ty::ParamEnv<'tcx>, + trait_ref: &ty::PolyTraitRef<'tcx>, + new_self_ty: Ty<'tcx>, ) -> PredicateObligation<'tcx>; fn maybe_report_ambiguity( @@ -1380,16 +1383,24 @@ impl<'a, 'tcx> InferCtxtPrivExt<'tcx> for InferCtxt<'a, 'tcx> { } } - fn mk_obligation_for_def_id( + fn mk_trait_obligation_with_new_self_ty( &self, - def_id: DefId, - output_ty: Ty<'tcx>, - cause: ObligationCause<'tcx>, param_env: ty::ParamEnv<'tcx>, + trait_ref: &ty::PolyTraitRef<'tcx>, + new_self_ty: Ty<'tcx>, ) -> PredicateObligation<'tcx> { - let new_trait_ref = - ty::TraitRef { def_id, substs: self.tcx.mk_substs_trait(output_ty, &[]) }; - Obligation::new(cause, param_env, new_trait_ref.without_const().to_predicate(self.tcx)) + assert!(!new_self_ty.has_escaping_bound_vars()); + + let trait_ref = trait_ref.map_bound_ref(|tr| ty::TraitRef { + substs: self.tcx.mk_substs_trait(new_self_ty, &tr.substs[1..]), + ..*tr + }); + + Obligation::new( + ObligationCause::dummy(), + param_env, + trait_ref.without_const().to_predicate(self.tcx), + ) } fn maybe_report_ambiguity( diff --git a/src/librustc_trait_selection/traits/error_reporting/suggestions.rs b/src/librustc_trait_selection/traits/error_reporting/suggestions.rs index 50a59469d8530..5c85855535e38 100644 --- a/src/librustc_trait_selection/traits/error_reporting/suggestions.rs +++ b/src/librustc_trait_selection/traits/error_reporting/suggestions.rs @@ -532,14 +532,17 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> { }; let msg = format!("use parentheses to call the {}", callable); - let obligation = self.mk_obligation_for_def_id( - trait_ref.def_id(), - output_ty.skip_binder(), - obligation.cause.clone(), - obligation.param_env, - ); + // `mk_trait_obligation_with_new_self_ty` only works for types with no escaping bound + // variables, so bail out if we have any. + let output_ty = match output_ty.no_bound_vars() { + Some(ty) => ty, + None => return, + }; + + let new_obligation = + self.mk_trait_obligation_with_new_self_ty(obligation.param_env, trait_ref, output_ty); - match self.evaluate_obligation(&obligation) { + match self.evaluate_obligation(&new_obligation) { Ok( EvaluationResult::EvaluatedToOk | EvaluationResult::EvaluatedToOkModuloRegions @@ -694,7 +697,6 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> { err: &mut DiagnosticBuilder<'_>, trait_ref: &ty::Binder>, ) { - let trait_ref = trait_ref.skip_binder(); let span = obligation.cause.span; if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) { @@ -705,17 +707,16 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> { return; } - let mut trait_type = trait_ref.self_ty(); + let mut suggested_ty = trait_ref.self_ty(); for refs_remaining in 0..refs_number { - if let ty::Ref(_, t_type, _) = trait_type.kind { - trait_type = t_type; + if let ty::Ref(_, inner_ty, _) = suggested_ty.kind { + suggested_ty = inner_ty; - let new_obligation = self.mk_obligation_for_def_id( - trait_ref.def_id, - trait_type, - ObligationCause::dummy(), + let new_obligation = self.mk_trait_obligation_with_new_self_ty( obligation.param_env, + trait_ref, + suggested_ty, ); if self.predicate_may_hold(&new_obligation) { @@ -782,20 +783,20 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> { return; } - let trait_type = match mutability { + let suggested_ty = match mutability { hir::Mutability::Mut => self.tcx.mk_imm_ref(region, t_type), hir::Mutability::Not => self.tcx.mk_mut_ref(region, t_type), }; - let new_obligation = self.mk_obligation_for_def_id( - trait_ref.skip_binder().def_id, - trait_type, - ObligationCause::dummy(), + let new_obligation = self.mk_trait_obligation_with_new_self_ty( obligation.param_env, + &trait_ref, + suggested_ty, ); - - if self.evaluate_obligation_no_overflow(&new_obligation).must_apply_modulo_regions() - { + let suggested_ty_would_satisfy_obligation = self + .evaluate_obligation_no_overflow(&new_obligation) + .must_apply_modulo_regions(); + if suggested_ty_would_satisfy_obligation { let sp = self .tcx .sess @@ -812,7 +813,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> { err.note(&format!( "`{}` is implemented for `{:?}`, but not for `{:?}`", trait_ref.print_only_trait_path(), - trait_type, + suggested_ty, trait_ref.skip_binder().self_ty(), )); } @@ -1891,7 +1892,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> { span: Span, ) { debug!( - "suggest_await_befor_try: obligation={:?}, span={:?}, trait_ref={:?}, trait_ref_self_ty={:?}", + "suggest_await_before_try: obligation={:?}, span={:?}, trait_ref={:?}, trait_ref_self_ty={:?}", obligation, span, trait_ref, @@ -1946,16 +1947,15 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> { ); debug!( - "suggest_await_befor_try: normalized_projection_type {:?}", + "suggest_await_before_try: normalized_projection_type {:?}", self.resolve_vars_if_possible(&normalized_ty) ); - let try_obligation = self.mk_obligation_for_def_id( - trait_ref.def_id(), - normalized_ty, - obligation.cause.clone(), + let try_obligation = self.mk_trait_obligation_with_new_self_ty( obligation.param_env, + trait_ref, + normalized_ty, ); - debug!("suggest_await_befor_try: try_trait_obligation {:?}", try_obligation); + debug!("suggest_await_before_try: try_trait_obligation {:?}", try_obligation); if self.predicate_may_hold(&try_obligation) && impls_future { if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) { if snippet.ends_with('?') { diff --git a/src/test/ui/suggestions/into-str.stderr b/src/test/ui/suggestions/into-str.stderr index 7414a7cc24c92..f7affdbf1b408 100644 --- a/src/test/ui/suggestions/into-str.stderr +++ b/src/test/ui/suggestions/into-str.stderr @@ -8,7 +8,6 @@ LL | foo(String::new()); | ^^^ the trait `std::convert::From` is not implemented for `&str` | = note: to coerce a `std::string::String` into a `&str`, use `&*` as a prefix - = note: `std::convert::From` is implemented for `&mut str`, but not for `&str` = note: required because of the requirements on the impl of `std::convert::Into<&str>` for `std::string::String` error: aborting due to previous error diff --git a/src/test/ui/suggestions/issue-71394-no-from-impl.rs b/src/test/ui/suggestions/issue-71394-no-from-impl.rs new file mode 100644 index 0000000000000..9ffcc3f7bc1c1 --- /dev/null +++ b/src/test/ui/suggestions/issue-71394-no-from-impl.rs @@ -0,0 +1,5 @@ +fn main() { + let data: &[u8] = &[0; 10]; + let _: &[i8] = data.into(); + //~^ ERROR the trait bound `&[i8]: std::convert::From<&[u8]>` is not satisfied +} diff --git a/src/test/ui/suggestions/issue-71394-no-from-impl.stderr b/src/test/ui/suggestions/issue-71394-no-from-impl.stderr new file mode 100644 index 0000000000000..84c73c2f67e70 --- /dev/null +++ b/src/test/ui/suggestions/issue-71394-no-from-impl.stderr @@ -0,0 +1,11 @@ +error[E0277]: the trait bound `&[i8]: std::convert::From<&[u8]>` is not satisfied + --> $DIR/issue-71394-no-from-impl.rs:3:25 + | +LL | let _: &[i8] = data.into(); + | ^^^^ the trait `std::convert::From<&[u8]>` is not implemented for `&[i8]` + | + = note: required because of the requirements on the impl of `std::convert::Into<&[i8]>` for `&[u8]` + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0277`.