From 69a8a88a6249bd6c68aeacb73d828609d530e2ba Mon Sep 17 00:00:00 2001 From: Dylan MacKenzie Date: Sat, 23 May 2020 11:11:20 -0700 Subject: [PATCH 1/8] `PolyTraitRef::self_ty` returns `Binder` --- src/librustc_middle/ty/sty.rs | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/src/librustc_middle/ty/sty.rs b/src/librustc_middle/ty/sty.rs index 0c9eef8093f33..9ced89cb17423 100644 --- a/src/librustc_middle/ty/sty.rs +++ b/src/librustc_middle/ty/sty.rs @@ -765,8 +765,8 @@ impl<'tcx> TraitRef<'tcx> { pub type PolyTraitRef<'tcx> = Binder>; impl<'tcx> PolyTraitRef<'tcx> { - pub fn self_ty(&self) -> Ty<'tcx> { - self.skip_binder().self_ty() + pub fn self_ty(&self) -> Binder> { + self.map_bound_ref(|tr| tr.self_ty()) } pub fn def_id(&self) -> DefId { From 09cd5473f5003abced0265d9fab26fc2b578f16b Mon Sep 17 00:00:00 2001 From: Dylan MacKenzie Date: Sat, 23 May 2020 11:12:06 -0700 Subject: [PATCH 2/8] Call `skip_binder` before `self_ty` to get old behavior --- .../traits/error_reporting/mod.rs | 32 ++++++++++++------- .../traits/error_reporting/suggestions.rs | 19 +++++++---- .../traits/specialize/mod.rs | 2 +- src/librustc_typeck/check/mod.rs | 2 +- src/librustdoc/clean/mod.rs | 4 +-- .../clippy_lints/src/future_not_send.rs | 2 +- 6 files changed, 39 insertions(+), 22 deletions(-) diff --git a/src/librustc_trait_selection/traits/error_reporting/mod.rs b/src/librustc_trait_selection/traits/error_reporting/mod.rs index 2aef8aaf0e303..fcd1ece17731a 100644 --- a/src/librustc_trait_selection/traits/error_reporting/mod.rs +++ b/src/librustc_trait_selection/traits/error_reporting/mod.rs @@ -289,7 +289,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> { ( Some(format!( "`?` couldn't convert the error to `{}`", - trait_ref.self_ty(), + trait_ref.skip_binder().self_ty(), )), Some( "the question mark operation (`?`) implicitly performs a \ @@ -339,7 +339,10 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> { if let Some(ret_span) = self.return_type_span(obligation) { err.span_label( ret_span, - &format!("expected `{}` because of this", trait_ref.self_ty()), + &format!( + "expected `{}` because of this", + trait_ref.skip_binder().self_ty() + ), ); } } @@ -352,7 +355,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> { "{}the trait `{}` is not implemented for `{}`", pre_message, trait_ref.print_only_trait_path(), - trait_ref.self_ty(), + trait_ref.skip_binder().self_ty(), ) }; @@ -638,7 +641,10 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> { return; } - let found_trait_ty = found_trait_ref.self_ty(); + let found_trait_ty = match found_trait_ref.self_ty().no_bound_vars() { + Some(ty) => ty, + None => return, + }; let found_did = match found_trait_ty.kind { ty::Closure(did, _) | ty::Foreign(did) | ty::FnDef(did, _) => Some(did), @@ -1352,11 +1358,15 @@ impl<'a, 'tcx> InferCtxtPrivExt<'tcx> for InferCtxt<'a, 'tcx> { ) { let get_trait_impl = |trait_def_id| { let mut trait_impl = None; - self.tcx.for_each_relevant_impl(trait_def_id, trait_ref.self_ty(), |impl_def_id| { - if trait_impl.is_none() { - trait_impl = Some(impl_def_id); - } - }); + self.tcx.for_each_relevant_impl( + trait_def_id, + trait_ref.skip_binder().self_ty(), + |impl_def_id| { + if trait_impl.is_none() { + trait_impl = Some(impl_def_id); + } + }, + ); trait_impl }; let required_trait_path = self.tcx.def_path_str(trait_ref.def_id()); @@ -1419,7 +1429,7 @@ impl<'a, 'tcx> InferCtxtPrivExt<'tcx> for InferCtxt<'a, 'tcx> { let mut err = match predicate.kind() { ty::PredicateKind::Trait(ref data, _) => { let trait_ref = data.to_poly_trait_ref(); - let self_ty = trait_ref.self_ty(); + let self_ty = trait_ref.skip_binder().self_ty(); debug!("self_ty {:?} {:?} trait_ref {:?}", self_ty, self_ty.kind, trait_ref); if predicate.references_error() { @@ -1537,7 +1547,7 @@ impl<'a, 'tcx> InferCtxtPrivExt<'tcx> for InferCtxt<'a, 'tcx> { } ty::PredicateKind::Projection(ref data) => { let trait_ref = data.to_poly_trait_ref(self.tcx); - let self_ty = trait_ref.self_ty(); + let self_ty = trait_ref.skip_binder().self_ty(); let ty = data.skip_binder().ty; if predicate.references_error() { return; diff --git a/src/librustc_trait_selection/traits/error_reporting/suggestions.rs b/src/librustc_trait_selection/traits/error_reporting/suggestions.rs index 0760bd523b7c3..8b45dd3084c61 100644 --- a/src/librustc_trait_selection/traits/error_reporting/suggestions.rs +++ b/src/librustc_trait_selection/traits/error_reporting/suggestions.rs @@ -318,7 +318,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> { trait_ref: ty::PolyTraitRef<'tcx>, body_id: hir::HirId, ) { - let self_ty = trait_ref.self_ty(); + let self_ty = trait_ref.skip_binder().self_ty(); let (param_ty, projection) = match &self_ty.kind { ty::Param(_) => (true, None), ty::Projection(projection) => (false, Some(projection)), @@ -524,7 +524,11 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> { trait_ref: &ty::Binder>, points_at_arg: bool, ) { - let self_ty = trait_ref.self_ty(); + let self_ty = match trait_ref.self_ty().no_bound_vars() { + None => return, + Some(ty) => ty, + }; + let (def_id, output_ty, callable) = match self_ty.kind { ty::Closure(def_id, substs) => (def_id, substs.as_closure().sig().output(), "closure"), ty::FnDef(def_id, _) => (def_id, self_ty.fn_sig(self.tcx).output(), "function"), @@ -828,6 +832,9 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> { span: Span, trait_ref: &ty::Binder>, ) { + let is_empty_tuple = + |ty: ty::Binder>| ty.skip_binder().kind == ty::Tuple(ty::List::empty()); + let hir = self.tcx.hir(); let parent_node = hir.get_parent_node(obligation.cause.body_id); let node = hir.find(parent_node); @@ -839,7 +846,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> { if let hir::ExprKind::Block(blk, _) = &body.value.kind { if sig.decl.output.span().overlaps(span) && blk.expr.is_none() - && "()" == &trait_ref.self_ty().to_string() + && is_empty_tuple(trait_ref.self_ty()) { // FIXME(estebank): When encountering a method with a trait // bound not satisfied in the return type with a body that has @@ -1270,7 +1277,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> { ObligationCauseCode::DerivedObligation(derived_obligation) | ObligationCauseCode::BuiltinDerivedObligation(derived_obligation) | ObligationCauseCode::ImplDerivedObligation(derived_obligation) => { - let ty = derived_obligation.parent_trait_ref.self_ty(); + let ty = derived_obligation.parent_trait_ref.skip_binder().self_ty(); debug!( "maybe_note_obligation_cause_for_async_await: \ parent_trait_ref={:?} self_ty.kind={:?}", @@ -1910,7 +1917,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> { let impls_future = self.tcx.type_implements_trait(( future_trait, - self_ty, + self_ty.skip_binder(), ty::List::empty(), obligation.param_env, )); @@ -1926,7 +1933,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> { let projection_ty = ty::ProjectionTy { // `T` substs: self.tcx.mk_substs_trait( - trait_ref.self_ty(), + trait_ref.self_ty().skip_binder(), self.fresh_substs_for_item(span, item_def_id), ), // `Future::Output` diff --git a/src/librustc_trait_selection/traits/specialize/mod.rs b/src/librustc_trait_selection/traits/specialize/mod.rs index f2b43754acaea..2b596be954267 100644 --- a/src/librustc_trait_selection/traits/specialize/mod.rs +++ b/src/librustc_trait_selection/traits/specialize/mod.rs @@ -496,7 +496,7 @@ fn to_pretty_impl_header(tcx: TyCtxt<'_>, impl_def_id: DefId) -> Option for (p, _) in predicates { if let Some(poly_trait_ref) = p.to_opt_poly_trait_ref() { if Some(poly_trait_ref.def_id()) == sized_trait { - types_without_default_bounds.remove(poly_trait_ref.self_ty()); + types_without_default_bounds.remove(poly_trait_ref.self_ty().skip_binder()); continue; } } diff --git a/src/librustc_typeck/check/mod.rs b/src/librustc_typeck/check/mod.rs index c452859414cfb..ecc30541baad5 100644 --- a/src/librustc_typeck/check/mod.rs +++ b/src/librustc_typeck/check/mod.rs @@ -3820,7 +3820,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { trait_ref: ty::PolyTraitRef<'tcx>, expected_vid: ty::TyVid, ) -> bool { - let self_ty = self.shallow_resolve(trait_ref.self_ty()); + let self_ty = self.shallow_resolve(trait_ref.skip_binder().self_ty()); debug!( "self_type_matches_expected_vid(trait_ref={:?}, self_ty={:?}, expected_vid={:?})", trait_ref, self_ty, expected_vid diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs index cf1a39232bc78..89f85473465a5 100644 --- a/src/librustdoc/clean/mod.rs +++ b/src/librustdoc/clean/mod.rs @@ -501,7 +501,7 @@ impl<'a> Clean for ty::PolyTraitPredicate<'a> { fn clean(&self, cx: &DocContext<'_>) -> WherePredicate { let poly_trait_ref = self.map_bound(|pred| pred.trait_ref); WherePredicate::BoundPredicate { - ty: poly_trait_ref.self_ty().clean(cx), + ty: poly_trait_ref.skip_binder().self_ty().clean(cx), bounds: vec![poly_trait_ref.clean(cx)], } } @@ -756,7 +756,7 @@ impl<'a, 'tcx> Clean for (&'a ty::Generics, ty::GenericPredicates<'tcx let mut projection = None; let param_idx = (|| { if let Some(trait_ref) = p.to_opt_poly_trait_ref() { - if let ty::Param(param) = trait_ref.self_ty().kind { + if let ty::Param(param) = trait_ref.skip_binder().self_ty().kind { return Some(param.index); } } else if let Some(outlives) = p.to_opt_type_outlives() { diff --git a/src/tools/clippy/clippy_lints/src/future_not_send.rs b/src/tools/clippy/clippy_lints/src/future_not_send.rs index 0a02aa7533c17..17dd3cd5493e7 100644 --- a/src/tools/clippy/clippy_lints/src/future_not_send.rs +++ b/src/tools/clippy/clippy_lints/src/future_not_send.rs @@ -95,7 +95,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for FutureNotSend { let trait_ref = trait_pred.to_poly_trait_ref(); db.note(&*format!( "`{}` doesn't implement `{}`", - trait_ref.self_ty(), + trait_ref.skip_binder().self_ty(), trait_ref.print_only_trait_path(), )); } From 4e4b1edda850157ea2e65b97ed77b2bef934cb85 Mon Sep 17 00:00:00 2001 From: Ross MacArthur Date: Mon, 25 May 2020 09:23:00 +0200 Subject: [PATCH 3/8] Add test for old compiler ICE when using `Borrow` --- .../ui/issues/issue-50687-ice-on-borrow.rs | 41 +++++++++++++++++++ .../issues/issue-50687-ice-on-borrow.stderr | 16 ++++++++ 2 files changed, 57 insertions(+) create mode 100644 src/test/ui/issues/issue-50687-ice-on-borrow.rs create mode 100644 src/test/ui/issues/issue-50687-ice-on-borrow.stderr diff --git a/src/test/ui/issues/issue-50687-ice-on-borrow.rs b/src/test/ui/issues/issue-50687-ice-on-borrow.rs new file mode 100644 index 0000000000000..7a8a12c2a93af --- /dev/null +++ b/src/test/ui/issues/issue-50687-ice-on-borrow.rs @@ -0,0 +1,41 @@ +// This previously caused an ICE at: +// librustc/traits/structural_impls.rs:180: impossible case reached + +#![no_main] + +use std::borrow::Borrow; +use std::io; +use std::io::Write; + +trait Constraint {} + +struct Container { + t: T, +} + +struct Borrowed; +struct Owned; + +impl<'a, T> Write for &'a Container +where + T: Constraint, + &'a T: Write, +{ + fn write(&mut self, buf: &[u8]) -> io::Result { + Ok(buf.len()) + } + + fn flush(&mut self) -> io::Result<()> { + Ok(()) + } +} + +impl Borrow for Owned { + fn borrow(&self) -> &Borrowed { + &Borrowed + } +} + +fn func(owned: Owned) { + let _: () = Borrow::borrow(&owned); //~ ERROR mismatched types +} diff --git a/src/test/ui/issues/issue-50687-ice-on-borrow.stderr b/src/test/ui/issues/issue-50687-ice-on-borrow.stderr new file mode 100644 index 0000000000000..f6adfc87dad33 --- /dev/null +++ b/src/test/ui/issues/issue-50687-ice-on-borrow.stderr @@ -0,0 +1,16 @@ +error[E0308]: mismatched types + --> $DIR/issue-50687-ice-on-borrow.rs:40:17 + | +LL | let _: () = Borrow::borrow(&owned); + | -- ^^^^^^^^^^^^^^^^^^^^^^ + | | | + | | expected `()`, found reference + | | help: consider dereferencing the borrow: `*Borrow::borrow(&owned)` + | expected due to this + | + = note: expected unit type `()` + found reference `&_` + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0308`. From ee6e705d91a7b19aa2d029b21396c70e2129f741 Mon Sep 17 00:00:00 2001 From: Diggory Blake Date: Sun, 24 May 2020 13:11:12 +0100 Subject: [PATCH 4/8] Fix UB in Arc Use raw pointers to avoid making any assertions about the data field. --- src/liballoc/sync.rs | 35 ++++++++++++++++++++++++++--------- 1 file changed, 26 insertions(+), 9 deletions(-) diff --git a/src/liballoc/sync.rs b/src/liballoc/sync.rs index 2bcf763354247..385506dc7a13d 100644 --- a/src/liballoc/sync.rs +++ b/src/liballoc/sync.rs @@ -866,12 +866,10 @@ impl Arc { unsafe fn drop_slow(&mut self) { // Destroy the data at this time, even though we may not free the box // allocation itself (there may still be weak pointers lying around). - ptr::drop_in_place(&mut self.ptr.as_mut().data); + ptr::drop_in_place(Self::get_mut_unchecked(self)); - if self.inner().weak.fetch_sub(1, Release) == 1 { - acquire!(self.inner().weak); - Global.dealloc(self.ptr.cast(), Layout::for_value(self.ptr.as_ref())) - } + // Drop the weak ref collectively held by all strong references + drop(Weak { ptr: self.ptr }); } #[inline] @@ -1201,7 +1199,7 @@ impl Arc { // As with `get_mut()`, the unsafety is ok because our reference was // either unique to begin with, or became one upon cloning the contents. - unsafe { &mut this.ptr.as_mut().data } + unsafe { Self::get_mut_unchecked(this) } } } @@ -1277,7 +1275,9 @@ impl Arc { #[inline] #[unstable(feature = "get_mut_unchecked", issue = "63292")] pub unsafe fn get_mut_unchecked(this: &mut Self) -> &mut T { - &mut this.ptr.as_mut().data + // We are careful to *not* create a reference covering the "count" fields, as + // this would alias with concurrent access to the reference counts (e.g. by `Weak`). + &mut (*this.ptr.as_ptr()).data } /// Determine whether this is the unique reference (including weak refs) to @@ -1568,6 +1568,13 @@ impl Weak { } } +/// Helper type to allow accessing the reference counts without +/// making any assertions about the data field. +struct WeakInner<'a> { + weak: &'a atomic::AtomicUsize, + strong: &'a atomic::AtomicUsize, +} + impl Weak { /// Attempts to upgrade the `Weak` pointer to an [`Arc`], delaying /// dropping of the inner value if successful. @@ -1673,8 +1680,18 @@ impl Weak { /// Returns `None` when the pointer is dangling and there is no allocated `ArcInner`, /// (i.e., when this `Weak` was created by `Weak::new`). #[inline] - fn inner(&self) -> Option<&ArcInner> { - if is_dangling(self.ptr) { None } else { Some(unsafe { self.ptr.as_ref() }) } + fn inner(&self) -> Option> { + if is_dangling(self.ptr) { + None + } else { + // We are careful to *not* create a reference covering the "data" field, as + // the field may be mutated concurrently (for example, if the last `Arc` + // is dropped, the data field will be dropped in-place). + Some(unsafe { + let ptr = self.ptr.as_ptr(); + WeakInner { strong: &(*ptr).strong, weak: &(*ptr).weak } + }) + } } /// Returns `true` if the two `Weak`s point to the same allocation (similar to From b9ba4b3810a4f818d2a1e4eb5b17841bd799e519 Mon Sep 17 00:00:00 2001 From: Guillaume Gomez Date: Tue, 26 May 2020 10:47:54 +0200 Subject: [PATCH 5/8] Small cell example update --- src/libcore/cell.rs | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/src/libcore/cell.rs b/src/libcore/cell.rs index 0f2665eba6f22..40a4fb50c9970 100644 --- a/src/libcore/cell.rs +++ b/src/libcore/cell.rs @@ -850,11 +850,11 @@ impl RefCell { /// ``` /// use std::cell::RefCell; /// - /// let c = RefCell::new(5); + /// let c = RefCell::new("hello".to_owned()); /// - /// *c.borrow_mut() = 7; + /// *c.borrow_mut() = "bonjour".to_owned(); /// - /// assert_eq!(*c.borrow(), 7); + /// assert_eq!(&*c.borrow(), "bonjour"); /// ``` /// /// An example of panic: From 1c30c9e92bdae1814dbae9367f214b4819cdd0de Mon Sep 17 00:00:00 2001 From: Aaron Hill Date: Tue, 26 May 2020 14:26:11 -0400 Subject: [PATCH 6/8] Don't bail out of trait selection when predicate references an error Fixes #72590 With PR #70551, observing a `ty::Error` guarantees that compilation is going to fail. Therefore, there are no soundness impliciations to continuing on when we encounter a `ty::Error` - we can only affect whether or not additional error messags are emitted. By not bailing out, we avoid incorrectly determining that types are `!Sized` when a type error is present, which allows us to avoid emitting additional spurious error messages. The original comment mentioned this code being shared by coherence - howver, this change resulted in no diagnostic changes in any of the existing tests. --- src/librustc_trait_selection/traits/select.rs | 11 -------- .../issue-72590-type-error-sized.rs | 22 +++++++++++++++ .../issue-72590-type-error-sized.stderr | 28 +++++++++++++++++++ 3 files changed, 50 insertions(+), 11 deletions(-) create mode 100644 src/test/ui/async-await/issue-72590-type-error-sized.rs create mode 100644 src/test/ui/async-await/issue-72590-type-error-sized.stderr diff --git a/src/librustc_trait_selection/traits/select.rs b/src/librustc_trait_selection/traits/select.rs index 9b3381066a17b..32bd895f85162 100644 --- a/src/librustc_trait_selection/traits/select.rs +++ b/src/librustc_trait_selection/traits/select.rs @@ -1040,17 +1040,6 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> { &mut self, stack: &TraitObligationStack<'o, 'tcx>, ) -> SelectionResult<'tcx, SelectionCandidate<'tcx>> { - if stack.obligation.predicate.references_error() { - // If we encounter a `Error`, we generally prefer the - // most "optimistic" result in response -- that is, the - // one least likely to report downstream errors. But - // because this routine is shared by coherence and by - // trait selection, there isn't an obvious "right" choice - // here in that respect, so we opt to just return - // ambiguity and let the upstream clients sort it out. - return Ok(None); - } - if let Some(conflict) = self.is_knowable(stack) { debug!("coherence stage: not knowable"); if self.intercrate_ambiguity_causes.is_some() { diff --git a/src/test/ui/async-await/issue-72590-type-error-sized.rs b/src/test/ui/async-await/issue-72590-type-error-sized.rs new file mode 100644 index 0000000000000..00e098d43e073 --- /dev/null +++ b/src/test/ui/async-await/issue-72590-type-error-sized.rs @@ -0,0 +1,22 @@ +// Regression test for issue #72590 +// Tests that we don't emit a spurious "size cannot be statically determined" error +// edition:2018 + +struct Foo { + foo: Nonexistent, //~ ERROR cannot find + other: str +} + +struct Bar { + test: Missing //~ ERROR cannot find +} + +impl Foo { + async fn frob(self) {} //~ ERROR the size +} + +impl Bar { + async fn myfn(self) {} +} + +fn main() {} diff --git a/src/test/ui/async-await/issue-72590-type-error-sized.stderr b/src/test/ui/async-await/issue-72590-type-error-sized.stderr new file mode 100644 index 0000000000000..603895b598c16 --- /dev/null +++ b/src/test/ui/async-await/issue-72590-type-error-sized.stderr @@ -0,0 +1,28 @@ +error[E0412]: cannot find type `Nonexistent` in this scope + --> $DIR/issue-72590-type-error-sized.rs:6:10 + | +LL | foo: Nonexistent, + | ^^^^^^^^^^^ not found in this scope + +error[E0412]: cannot find type `Missing` in this scope + --> $DIR/issue-72590-type-error-sized.rs:11:11 + | +LL | test: Missing + | ^^^^^^^ not found in this scope + +error[E0277]: the size for values of type `str` cannot be known at compilation time + --> $DIR/issue-72590-type-error-sized.rs:15:19 + | +LL | async fn frob(self) {} + | ^^^^ doesn't have a size known at compile-time + | + = help: within `Foo`, the trait `std::marker::Sized` is not implemented for `str` + = note: to learn more, visit + = note: required because it appears within the type `Foo` + = note: all local variables must have a statically known size + = help: unsized locals are gated as an unstable feature + +error: aborting due to 3 previous errors + +Some errors have detailed explanations: E0277, E0412. +For more information about an error, try `rustc --explain E0277`. From b60fe399f3148c4af4ea568b262211661cab37ab Mon Sep 17 00:00:00 2001 From: philipp Date: Tue, 26 May 2020 21:38:44 +0200 Subject: [PATCH 7/8] Add remark regarding DoubleEndedIterator --- src/libcore/iter/traits/double_ended.rs | 26 +++++++++++++++++++++++++ 1 file changed, 26 insertions(+) diff --git a/src/libcore/iter/traits/double_ended.rs b/src/libcore/iter/traits/double_ended.rs index cceb373d552a8..f6329c6c593ed 100644 --- a/src/libcore/iter/traits/double_ended.rs +++ b/src/libcore/iter/traits/double_ended.rs @@ -63,6 +63,32 @@ pub trait DoubleEndedIterator: Iterator { /// assert_eq!(None, iter.next()); /// assert_eq!(None, iter.next_back()); /// ``` + /// + /// # Remarks + /// + /// The elements yielded by `DoubleEndedIterator`'s methods may differ from + /// the ones yielded by `Iterator`'s methods: + /// + /// ``` + /// let vec = vec![(1, 'a'), (1, 'b'), (1, 'c'), (2, 'a'), (2, 'b')]; + /// let uniq_by_fst_comp = || { + /// let mut seen = std::collections::HashSet::new(); + /// vec.iter().copied().filter(move |x| seen.insert(x.0)) + /// }; + /// + /// assert_eq!(uniq_by_fst_comp().last(), Some((2, 'a'))); + /// assert_eq!(uniq_by_fst_comp().next_back(), Some((2, 'b'))); + /// + /// assert_eq!( + /// uniq_by_fst_comp().fold(vec![], |mut v, x| {v.push(x); v}), + /// vec![(1, 'a'), (2, 'a')] + /// ); + /// assert_eq!( + /// uniq_by_fst_comp().rfold(vec![], |mut v, x| {v.push(x); v}), + /// vec![(2, 'b'), (1, 'c')] + /// ); + /// ``` + /// #[stable(feature = "rust1", since = "1.0.0")] fn next_back(&mut self) -> Option; From f384cdcbecf46db38e46177700d29e881dcb53b7 Mon Sep 17 00:00:00 2001 From: Chris Simpkins Date: Tue, 26 May 2020 16:52:16 -0400 Subject: [PATCH 8/8] improve error message for unexpected comma token in multiline block confusing diagnostics, issue #72253 add test for confusing error message, issue-72253 remove is_multiline check, refactor to self.expect(&token:Semi) update issue-72253 tests return Ok --- src/librustc_parse/parser/diagnostics.rs | 13 +++++++++++++ src/test/ui/issues/issue-72253.rs | 6 ++++++ src/test/ui/issues/issue-72253.stderr | 10 ++++++++++ 3 files changed, 29 insertions(+) create mode 100644 src/test/ui/issues/issue-72253.rs create mode 100644 src/test/ui/issues/issue-72253.stderr diff --git a/src/librustc_parse/parser/diagnostics.rs b/src/librustc_parse/parser/diagnostics.rs index 93c7faf22a73f..079059ec75146 100644 --- a/src/librustc_parse/parser/diagnostics.rs +++ b/src/librustc_parse/parser/diagnostics.rs @@ -934,6 +934,19 @@ impl<'a> Parser<'a> { return self.expect(&token::Semi).map(drop); } else if !sm.is_multiline(self.prev_token.span.until(self.token.span)) { // The current token is in the same line as the prior token, not recoverable. + } else if [token::Comma, token::Colon].contains(&self.token.kind) + && &self.prev_token.kind == &token::CloseDelim(token::Paren) + { + // Likely typo: The current token is on a new line and is expected to be + // `.`, `;`, `?`, or an operator after a close delimiter token. + // + // let a = std::process::Command::new("echo") + // .arg("1") + // ,arg("2") + // ^ + // https://github.com/rust-lang/rust/issues/72253 + self.expect(&token::Semi)?; + return Ok(()); } else if self.look_ahead(1, |t| { t == &token::CloseDelim(token::Brace) || t.can_begin_expr() && t.kind != token::Colon }) && [token::Comma, token::Colon].contains(&self.token.kind) diff --git a/src/test/ui/issues/issue-72253.rs b/src/test/ui/issues/issue-72253.rs new file mode 100644 index 0000000000000..6f9af73b039e4 --- /dev/null +++ b/src/test/ui/issues/issue-72253.rs @@ -0,0 +1,6 @@ +fn main() { + let a = std::process::Command::new("echo") + .arg("1") + ,arg("2") //~ ERROR expected one of `.`, `;`, `?`, or an operator, found `,` + .output(); +} diff --git a/src/test/ui/issues/issue-72253.stderr b/src/test/ui/issues/issue-72253.stderr new file mode 100644 index 0000000000000..3819fd92a9e21 --- /dev/null +++ b/src/test/ui/issues/issue-72253.stderr @@ -0,0 +1,10 @@ +error: expected one of `.`, `;`, `?`, or an operator, found `,` + --> $DIR/issue-72253.rs:4:9 + | +LL | .arg("1") + | - expected one of `.`, `;`, `?`, or an operator +LL | ,arg("2") + | ^ unexpected token + +error: aborting due to previous error +