diff --git a/src/libcore/ops/function.rs b/src/libcore/ops/function.rs index 4a0a2720fe441..35790324a2f62 100644 --- a/src/libcore/ops/function.rs +++ b/src/libcore/ops/function.rs @@ -137,10 +137,6 @@ pub trait Fn : FnMut { #[rustc_paren_sugar] #[rustc_on_unimplemented( on(Args="()", note="wrap the `{Self}` in a closure with no arguments: `|| {{ /* code */ }}"), - on( - all(Args="(char,)", _Self="std::string::String"), - note="borrowing the `{Self}` might fix the problem" - ), message="expected a `{FnMut}<{Args}>` closure, found `{Self}`", label="expected an `FnMut<{Args}>` closure, found `{Self}`", )] diff --git a/src/librustc/traits/error_reporting.rs b/src/librustc/traits/error_reporting.rs index 697bb3f467c54..f511862b37b84 100644 --- a/src/librustc/traits/error_reporting.rs +++ b/src/librustc/traits/error_reporting.rs @@ -33,7 +33,7 @@ use crate::ty::subst::Subst; use crate::ty::SubtypePredicate; use crate::util::nodemap::{FxHashMap, FxHashSet}; -use errors::{Applicability, DiagnosticBuilder, pluralize}; +use errors::{Applicability, DiagnosticBuilder, pluralise, Style}; use std::fmt; use syntax::ast; use syntax::symbol::{sym, kw}; @@ -723,7 +723,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> { post_message, pre_message, ) = self.get_parent_trait_ref(&obligation.cause.code) - .map(|t| (format!(" in `{}`", t), format!("within `{}`, ", t))) + .map(|t| (format!(" in `{}`", t), format!("within `{}`, ", t))) .unwrap_or_default(); let OnUnimplementedNote { @@ -787,6 +787,16 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> { self.suggest_borrow_on_unsized_slice(&obligation.cause.code, &mut err); self.suggest_fn_call(&obligation, &mut err, &trait_ref, points_at_arg); self.suggest_remove_reference(&obligation, &mut err, &trait_ref); + if self.suggest_add_reference_to_arg( + &obligation, + &mut err, + &trait_ref, + points_at_arg, + ) { + self.note_obligation_cause(&mut err, obligation); + err.emit(); + return; + } self.suggest_semicolon_removal(&obligation, &mut err, span, &trait_ref); // Try to report a help message @@ -1302,6 +1312,66 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> { } } + fn suggest_add_reference_to_arg( + &self, + obligation: &PredicateObligation<'tcx>, + err: &mut DiagnosticBuilder<'tcx>, + trait_ref: &ty::Binder>, + points_at_arg: bool, + ) -> bool { + if !points_at_arg { + return false; + } + + let span = obligation.cause.span; + let param_env = obligation.param_env; + let trait_ref = trait_ref.skip_binder(); + + if let ObligationCauseCode::ImplDerivedObligation(obligation) = &obligation.cause.code { + // Try to apply the original trait binding obligation by borrowing. + let self_ty = trait_ref.self_ty(); + let found = self_ty.to_string(); + let new_self_ty = self.tcx.mk_imm_ref(self.tcx.lifetimes.re_static, self_ty); + let substs = self.tcx.mk_substs_trait(new_self_ty, &[]); + let new_trait_ref = ty::TraitRef::new(obligation.parent_trait_ref.def_id(), substs); + let new_obligation = Obligation::new( + ObligationCause::dummy(), + param_env, + new_trait_ref.to_predicate(), + ); + if self.predicate_may_hold(&new_obligation) { + if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) { + // We have a very specific type of error, where just borrowing this argument + // might solve the problem. In cases like this, the important part is the + // original type obligation, not the last one that failed, which is arbitrary. + // Because of this, we modify the error to refer to the original obligation and + // return early in the caller. + err.message = vec![( + format!( + "the trait bound `{}: {}` is not satisfied", + found, + obligation.parent_trait_ref.skip_binder(), + ), + Style::NoStyle, + )]; + if snippet.starts_with('&') { + // This is already a literal borrow and the obligation is failing + // somewhere else in the obligation chain. Do not suggest non-sense. + return false; + } + err.span_suggestion( + span, + "consider borrowing here", + format!("&{}", snippet), + Applicability::MachineApplicable, + ); + return true; + } + } + } + false + } + /// Whenever references are used by mistake, like `for (i, e) in &vec.iter().enumerate()`, /// suggest removing these references until we reach a type that implements the trait. fn suggest_remove_reference( diff --git a/src/test/ui/derives/deriving-copyclone.rs b/src/test/ui/derives/deriving-copyclone.rs index 4565412bff7f3..06b3157a77a84 100644 --- a/src/test/ui/derives/deriving-copyclone.rs +++ b/src/test/ui/derives/deriving-copyclone.rs @@ -28,10 +28,10 @@ fn main() { is_clone(B { a: 1, b: 2 }); // B cannot be copied or cloned - is_copy(B { a: 1, b: C }); //~ERROR Copy - is_clone(B { a: 1, b: C }); //~ERROR Clone + is_copy(B { a: 1, b: C }); //~ ERROR Copy + is_clone(B { a: 1, b: C }); //~ ERROR Clone // B can be cloned but not copied - is_copy(B { a: 1, b: D }); //~ERROR Copy + is_copy(B { a: 1, b: D }); //~ ERROR Copy is_clone(B { a: 1, b: D }); } diff --git a/src/test/ui/derives/deriving-copyclone.stderr b/src/test/ui/derives/deriving-copyclone.stderr index 4cca14ae089e9..561706469c648 100644 --- a/src/test/ui/derives/deriving-copyclone.stderr +++ b/src/test/ui/derives/deriving-copyclone.stderr @@ -5,7 +5,10 @@ LL | fn is_copy(_: T) {} | ------- ---- required by this bound in `is_copy` ... LL | is_copy(B { a: 1, b: C }); - | ^^^^^^^^^^^^^^^^ the trait `std::marker::Copy` is not implemented for `C` + | ^^^^^^^^^^^^^^^^ + | | + | the trait `std::marker::Copy` is not implemented for `C` + | help: consider borrowing here: `&B { a: 1, b: C }` | = note: required because of the requirements on the impl of `std::marker::Copy` for `B` @@ -16,7 +19,10 @@ LL | fn is_clone(_: T) {} | -------- ----- required by this bound in `is_clone` ... LL | is_clone(B { a: 1, b: C }); - | ^^^^^^^^^^^^^^^^ the trait `std::clone::Clone` is not implemented for `C` + | ^^^^^^^^^^^^^^^^ + | | + | the trait `std::clone::Clone` is not implemented for `C` + | help: consider borrowing here: `&B { a: 1, b: C }` | = note: required because of the requirements on the impl of `std::clone::Clone` for `B` @@ -27,7 +33,10 @@ LL | fn is_copy(_: T) {} | ------- ---- required by this bound in `is_copy` ... LL | is_copy(B { a: 1, b: D }); - | ^^^^^^^^^^^^^^^^ the trait `std::marker::Copy` is not implemented for `D` + | ^^^^^^^^^^^^^^^^ + | | + | the trait `std::marker::Copy` is not implemented for `D` + | help: consider borrowing here: `&B { a: 1, b: D }` | = note: required because of the requirements on the impl of `std::marker::Copy` for `B` diff --git a/src/test/ui/kindck/kindck-impl-type-params-2.rs b/src/test/ui/kindck/kindck-impl-type-params-2.rs index ac9cc1a08f33d..d5fcc68a759cb 100644 --- a/src/test/ui/kindck/kindck-impl-type-params-2.rs +++ b/src/test/ui/kindck/kindck-impl-type-params-2.rs @@ -11,5 +11,5 @@ fn take_param(foo: &T) { } fn main() { let x: Box<_> = box 3; take_param(&x); - //~^ ERROR `std::boxed::Box<{integer}>: std::marker::Copy` is not satisfied + //~^ ERROR the trait bound `std::boxed::Box<{integer}>: Foo` is not satisfied } diff --git a/src/test/ui/kindck/kindck-impl-type-params-2.stderr b/src/test/ui/kindck/kindck-impl-type-params-2.stderr index 8e98911324411..318b7b0f10a0a 100644 --- a/src/test/ui/kindck/kindck-impl-type-params-2.stderr +++ b/src/test/ui/kindck/kindck-impl-type-params-2.stderr @@ -1,4 +1,4 @@ -error[E0277]: the trait bound `std::boxed::Box<{integer}>: std::marker::Copy` is not satisfied +error[E0277]: the trait bound `std::boxed::Box<{integer}>: Foo` is not satisfied --> $DIR/kindck-impl-type-params-2.rs:13:16 | LL | fn take_param(foo: &T) { } diff --git a/src/test/ui/kindck/kindck-inherited-copy-bound.curr.stderr b/src/test/ui/kindck/kindck-inherited-copy-bound.curr.stderr index a93f4686496ac..da1a7a7520e07 100644 --- a/src/test/ui/kindck/kindck-inherited-copy-bound.curr.stderr +++ b/src/test/ui/kindck/kindck-inherited-copy-bound.curr.stderr @@ -1,4 +1,4 @@ -error[E0277]: the trait bound `std::boxed::Box<{integer}>: std::marker::Copy` is not satisfied +error[E0277]: the trait bound `std::boxed::Box<{integer}>: Foo` is not satisfied --> $DIR/kindck-inherited-copy-bound.rs:21:16 | LL | fn take_param(foo: &T) { } diff --git a/src/test/ui/suggestions/issue-62843.stderr b/src/test/ui/suggestions/issue-62843.stderr index b5801e9162fb3..9535bf1b2ced5 100644 --- a/src/test/ui/suggestions/issue-62843.stderr +++ b/src/test/ui/suggestions/issue-62843.stderr @@ -1,11 +1,13 @@ -error[E0277]: expected a `std::ops::FnMut<(char,)>` closure, found `std::string::String` +error[E0277]: the trait bound `std::string::String: std::str::pattern::Pattern<'_>` is not satisfied --> $DIR/issue-62843.rs:4:32 | LL | println!("{:?}", line.find(pattern)); - | ^^^^^^^ expected an `FnMut<(char,)>` closure, found `std::string::String` + | ^^^^^^^ + | | + | expected an `FnMut<(char,)>` closure, found `std::string::String` + | help: consider borrowing here: `&pattern` | = help: the trait `std::ops::FnMut<(char,)>` is not implemented for `std::string::String` - = note: borrowing the `std::string::String` might fix the problem = note: required because of the requirements on the impl of `std::str::pattern::Pattern<'_>` for `std::string::String` error: aborting due to previous error diff --git a/src/test/ui/traits/traits-negative-impls.rs b/src/test/ui/traits/traits-negative-impls.rs index fb9a3a99748d0..8ed39986781cd 100644 --- a/src/test/ui/traits/traits-negative-impls.rs +++ b/src/test/ui/traits/traits-negative-impls.rs @@ -46,7 +46,7 @@ fn dummy2() { impl !Send for TestType {} is_send(Box::new(TestType)); - //~^ ERROR `dummy2::TestType` cannot be sent between threads safely + //~^ ERROR the trait bound `dummy2::TestType: std::marker::Send` is not satisfied } fn dummy3() { @@ -64,5 +64,5 @@ fn main() { // This will complain about a missing Send impl because `Sync` is implement *just* // for T that are `Send`. Look at #20366 and #19950 is_sync(Outer2(TestType)); - //~^ ERROR `main::TestType` cannot be sent between threads safely + //~^ ERROR the trait bound `main::TestType: std::marker::Sync` is not satisfied } diff --git a/src/test/ui/traits/traits-negative-impls.stderr b/src/test/ui/traits/traits-negative-impls.stderr index 22b6d2a0c4e98..448bb90205d03 100644 --- a/src/test/ui/traits/traits-negative-impls.stderr +++ b/src/test/ui/traits/traits-negative-impls.stderr @@ -43,14 +43,17 @@ LL | is_send((8, TestType)); = help: within `({integer}, dummy1c::TestType)`, the trait `std::marker::Send` is not implemented for `dummy1c::TestType` = note: required because it appears within the type `({integer}, dummy1c::TestType)` -error[E0277]: `dummy2::TestType` cannot be sent between threads safely +error[E0277]: the trait bound `dummy2::TestType: std::marker::Send` is not satisfied --> $DIR/traits-negative-impls.rs:48:13 | LL | fn is_send(_: T) {} | ------- ---- required by this bound in `is_send` ... LL | is_send(Box::new(TestType)); - | ^^^^^^^^^^^^^^^^^^ `dummy2::TestType` cannot be sent between threads safely + | ^^^^^^^^^^^^^^^^^^ + | | + | `dummy2::TestType` cannot be sent between threads safely + | help: consider borrowing here: `&Box::new(TestType)` | = help: the trait `std::marker::Send` is not implemented for `dummy2::TestType` = note: required because of the requirements on the impl of `std::marker::Send` for `std::ptr::Unique` @@ -70,14 +73,17 @@ LL | is_send(Box::new(Outer2(TestType))); = note: required because of the requirements on the impl of `std::marker::Send` for `std::ptr::Unique>` = note: required because it appears within the type `std::boxed::Box>` -error[E0277]: `main::TestType` cannot be sent between threads safely +error[E0277]: the trait bound `main::TestType: std::marker::Sync` is not satisfied --> $DIR/traits-negative-impls.rs:66:13 | LL | fn is_sync(_: T) {} | ------- ---- required by this bound in `is_sync` ... LL | is_sync(Outer2(TestType)); - | ^^^^^^^^^^^^^^^^ `main::TestType` cannot be sent between threads safely + | ^^^^^^^^^^^^^^^^ + | | + | `main::TestType` cannot be sent between threads safely + | help: consider borrowing here: `&Outer2(TestType)` | = help: the trait `std::marker::Send` is not implemented for `main::TestType` = note: required because of the requirements on the impl of `std::marker::Sync` for `Outer2`