diff --git a/src/librustc/hir/mod.rs b/src/librustc/hir/mod.rs index 8d83dd3279c64..f18846b8574df 100644 --- a/src/librustc/hir/mod.rs +++ b/src/librustc/hir/mod.rs @@ -402,6 +402,15 @@ pub enum GenericArg { Type(Ty), } +impl GenericArg { + pub fn span(&self) -> Span { + match self { + GenericArg::Lifetime(l) => l.span, + GenericArg::Type(t) => t.span, + } + } +} + #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)] pub struct GenericArgs { /// The generic arguments for this path segment. diff --git a/src/librustc_mir/borrow_check/nll/region_infer/error_reporting/region_name.rs b/src/librustc_mir/borrow_check/nll/region_infer/error_reporting/region_name.rs index bf8c9c8c3bef4..16dec2725ff04 100644 --- a/src/librustc_mir/borrow_check/nll/region_infer/error_reporting/region_name.rs +++ b/src/librustc_mir/borrow_check/nll/region_infer/error_reporting/region_name.rs @@ -10,9 +10,11 @@ use borrow_check::nll::region_infer::RegionInferenceContext; use borrow_check::nll::ToRegionVid; +use rustc::hir; use rustc::hir::def_id::DefId; use rustc::mir::{Local, Mir}; -use rustc::ty::{self, RegionVid, TyCtxt}; +use rustc::ty::subst::{Substs, UnpackedKind}; +use rustc::ty::{self, RegionVid, Ty, TyCtxt}; use rustc_data_structures::indexed_vec::Idx; use rustc_errors::DiagnosticBuilder; use syntax::ast::Name; @@ -60,7 +62,9 @@ impl<'tcx> RegionInferenceContext<'tcx> { self.give_name_from_error_region(tcx, mir_def_id, fr, counter, diag) .or_else(|| { - self.give_name_if_anonymous_region_appears_in_arguments(tcx, mir, fr, counter, diag) + self.give_name_if_anonymous_region_appears_in_arguments( + tcx, mir, mir_def_id, fr, counter, diag, + ) }) .or_else(|| { self.give_name_if_anonymous_region_appears_in_upvars(tcx, mir, fr, counter, diag) @@ -129,20 +133,24 @@ impl<'tcx> RegionInferenceContext<'tcx> { &self, tcx: TyCtxt<'_, '_, 'tcx>, mir: &Mir<'tcx>, + mir_def_id: DefId, fr: RegionVid, counter: &mut usize, diag: &mut DiagnosticBuilder<'_>, ) -> Option { let implicit_inputs = self.universal_regions.defining_ty.implicit_inputs(); - let argument_index = self.universal_regions + let argument_index = self + .universal_regions .unnormalized_input_tys .iter() .skip(implicit_inputs) .position(|arg_ty| { - debug!("give_name_if_anonymous_region_appears_in_arguments: arg_ty = {:?}", arg_ty); + debug!( + "give_name_if_anonymous_region_appears_in_arguments: arg_ty = {:?}", + arg_ty + ); tcx.any_free_region_meets(arg_ty, |r| r.to_region_vid() == fr) - })? - + implicit_inputs; + })?; debug!( "give_name_if_anonymous_region_appears_in_arguments: \ @@ -150,9 +158,23 @@ impl<'tcx> RegionInferenceContext<'tcx> { fr, argument_index, self.universal_regions.unnormalized_input_tys[argument_index], ); + let arg_ty = + self.universal_regions.unnormalized_input_tys[implicit_inputs + argument_index]; + if let Some(region_name) = self.give_name_if_we_can_match_hir_ty_from_argument( + tcx, + mir_def_id, + fr, + arg_ty, + argument_index, + counter, + diag, + ) { + return Some(region_name); + } + let region_name = self.synthesize_region_name(counter); - let argument_local = Local::new(argument_index + 1); + let argument_local = Local::new(argument_index + implicit_inputs + 1); let argument_span = mir.local_decls[argument_local].source_info.span; diag.span_label( argument_span, @@ -162,6 +184,240 @@ impl<'tcx> RegionInferenceContext<'tcx> { Some(region_name) } + fn give_name_if_we_can_match_hir_ty_from_argument( + &self, + tcx: TyCtxt<'_, '_, 'tcx>, + mir_def_id: DefId, + needle_fr: RegionVid, + argument_ty: Ty<'tcx>, + argument_index: usize, + counter: &mut usize, + diag: &mut DiagnosticBuilder<'_>, + ) -> Option { + let mir_node_id = tcx.hir.as_local_node_id(mir_def_id)?; + let fn_decl = tcx.hir.fn_decl(mir_node_id)?; + let argument_hir_ty: &hir::Ty = &fn_decl.inputs[argument_index]; + match argument_hir_ty.node { + // This indicates a variable with no type annotation, like + // `|x|`... in that case, we can't highlight the type but + // must highlight the variable. + hir::TyInfer => None, + + _ => self.give_name_if_we_can_match_hir_ty( + tcx, + needle_fr, + argument_ty, + argument_hir_ty, + counter, + diag, + ), + } + } + + /// Attempts to highlight the specific part of a type annotation + /// that contains the anonymous reference we want to give a name + /// to. For example, we might produce an annotation like this: + /// + /// ``` + /// | fn a(items: &[T]) -> Box> { + /// | - let's call the lifetime of this reference `'1` + /// ``` + /// + /// the way this works is that we match up `argument_ty`, which is + /// a `Ty<'tcx>` (the internal form of the type) with + /// `argument_hir_ty`, a `hir::Ty` (the syntax of the type + /// annotation). We are descending through the types stepwise, + /// looking in to find the region `needle_fr` in the internal + /// type. Once we find that, we can use the span of the `hir::Ty` + /// to add the highlight. + /// + /// This is a somewhat imperfect process, so long the way we also + /// keep track of the **closest** type we've found. If we fail to + /// find the exact `&` or `'_` to highlight, then we may fall back + /// to highlighting that closest type instead. + fn give_name_if_we_can_match_hir_ty( + &self, + tcx: TyCtxt<'_, '_, 'tcx>, + needle_fr: RegionVid, + argument_ty: Ty<'tcx>, + argument_hir_ty: &hir::Ty, + counter: &mut usize, + diag: &mut DiagnosticBuilder<'_>, + ) -> Option { + let search_stack: &mut Vec<(Ty<'tcx>, &hir::Ty)> = &mut Vec::new(); + + search_stack.push((argument_ty, argument_hir_ty)); + + let mut closest_match: &hir::Ty = argument_hir_ty; + + while let Some((ty, hir_ty)) = search_stack.pop() { + // While we search, also track the closet match. + if tcx.any_free_region_meets(&ty, |r| r.to_region_vid() == needle_fr) { + closest_match = hir_ty; + } + + match (&ty.sty, &hir_ty.node) { + // Check if the `argument_ty` is `&'X ..` where `'X` + // is the region we are looking for -- if so, and we have a `&T` + // on the RHS, then we want to highlight the `&` like so: + // + // & + // - let's call the lifetime of this reference `'1` + (ty::TyRef(region, referent_ty, _), hir::TyRptr(_lifetime, referent_hir_ty)) => { + if region.to_region_vid() == needle_fr { + let region_name = self.synthesize_region_name(counter); + + // Just grab the first character, the `&`. + let codemap = tcx.sess.codemap(); + let ampersand_span = codemap.start_point(hir_ty.span); + + diag.span_label( + ampersand_span, + format!( + "let's call the lifetime of this reference `{}`", + region_name + ), + ); + + return Some(region_name); + } + + // Otherwise, let's descend into the referent types. + search_stack.push((referent_ty, &referent_hir_ty.ty)); + } + + // Match up something like `Foo<'1>` + (ty::TyAdt(_adt_def, substs), hir::TyPath(hir::QPath::Resolved(None, path))) => { + if let Some(last_segment) = path.segments.last() { + if let Some(name) = self.match_adt_and_segment( + substs, + needle_fr, + last_segment, + counter, + diag, + search_stack, + ) { + return Some(name); + } + } + } + + // The following cases don't have lifetimes, so we + // just worry about trying to match up the rustc type + // with the HIR types: + (ty::TyTuple(elem_tys), hir::TyTup(elem_hir_tys)) => { + search_stack.extend(elem_tys.iter().cloned().zip(elem_hir_tys)); + } + + (ty::TySlice(elem_ty), hir::TySlice(elem_hir_ty)) + | (ty::TyArray(elem_ty, _), hir::TyArray(elem_hir_ty, _)) => { + search_stack.push((elem_ty, elem_hir_ty)); + } + + (ty::TyRawPtr(mut_ty), hir::TyPtr(mut_hir_ty)) => { + search_stack.push((mut_ty.ty, &mut_hir_ty.ty)); + } + + _ => { + // FIXME there are other cases that we could trace + } + } + } + + let region_name = self.synthesize_region_name(counter); + diag.span_label( + closest_match.span, + format!("lifetime `{}` appears in this type", region_name), + ); + + return Some(region_name); + } + + /// We've found an enum/struct/union type with the substitutions + /// `substs` and -- in the HIR -- a path type with the final + /// segment `last_segment`. Try to find a `'_` to highlight in + /// the generic args (or, if not, to produce new zipped pairs of + /// types+hir to search through). + fn match_adt_and_segment<'hir>( + &self, + substs: &'tcx Substs<'tcx>, + needle_fr: RegionVid, + last_segment: &'hir hir::PathSegment, + counter: &mut usize, + diag: &mut DiagnosticBuilder<'_>, + search_stack: &mut Vec<(Ty<'tcx>, &'hir hir::Ty)>, + ) -> Option { + // Did the user give explicit arguments? (e.g., `Foo<..>`) + let args = last_segment.args.as_ref()?; + let lifetime = self.try_match_adt_and_generic_args(substs, needle_fr, args, search_stack)?; + match lifetime.name { + hir::LifetimeName::Param(_) + | hir::LifetimeName::Static + | hir::LifetimeName::Underscore => { + let region_name = self.synthesize_region_name(counter); + let ampersand_span = lifetime.span; + diag.span_label(ampersand_span, format!("let's call this `{}`", region_name)); + return Some(region_name); + } + + hir::LifetimeName::Implicit => { + // In this case, the user left off the lifetime; so + // they wrote something like: + // + // ``` + // x: Foo + // ``` + // + // where the fully elaborated form is `Foo<'_, '1, + // T>`. We don't consider this a match; instead we let + // the "fully elaborated" type fallback above handle + // it. + return None; + } + } + } + + /// We've found an enum/struct/union type with the substitutions + /// `substs` and -- in the HIR -- a path with the generic + /// arguments `args`. If `needle_fr` appears in the args, return + /// the `hir::Lifetime` that corresponds to it. If not, push onto + /// `search_stack` the types+hir to search through. + fn try_match_adt_and_generic_args<'hir>( + &self, + substs: &'tcx Substs<'tcx>, + needle_fr: RegionVid, + args: &'hir hir::GenericArgs, + search_stack: &mut Vec<(Ty<'tcx>, &'hir hir::Ty)>, + ) -> Option<&'hir hir::Lifetime> { + for (kind, hir_arg) in substs.iter().zip(&args.args) { + match (kind.unpack(), hir_arg) { + (UnpackedKind::Lifetime(r), hir::GenericArg::Lifetime(lt)) => { + if r.to_region_vid() == needle_fr { + return Some(lt); + } + } + + (UnpackedKind::Type(ty), hir::GenericArg::Type(hir_ty)) => { + search_stack.push((ty, hir_ty)); + } + + (UnpackedKind::Lifetime(_), _) | (UnpackedKind::Type(_), _) => { + // I *think* that HIR lowering should ensure this + // doesn't happen, even in erroneous + // programs. Else we should use delay-span-bug. + span_bug!( + hir_arg.span(), + "unmatched subst and hir arg: found {:?} vs {:?}", + kind, + hir_arg, + ); + } + } + } + + None + } + /// Find a closure upvar that contains `fr` and label it with a /// fully elaborated type, returning something like `'1`. Result /// looks like: @@ -178,7 +434,8 @@ impl<'tcx> RegionInferenceContext<'tcx> { counter: &mut usize, diag: &mut DiagnosticBuilder<'_>, ) -> Option { - let upvar_index = self.universal_regions + let upvar_index = self + .universal_regions .defining_ty .upvar_tys(tcx) .position(|upvar_ty| { @@ -189,15 +446,16 @@ impl<'tcx> RegionInferenceContext<'tcx> { tcx.any_free_region_meets(&upvar_ty, |r| r.to_region_vid() == fr) })?; + let upvar_ty = self + .universal_regions + .defining_ty + .upvar_tys(tcx) + .nth(upvar_index); + debug!( "give_name_if_anonymous_region_appears_in_upvars: \ found {:?} in upvar {} which has type {:?}", - fr, - upvar_index, - self.universal_regions - .defining_ty - .upvar_tys(tcx) - .nth(upvar_index), + fr, upvar_index, upvar_ty, ); let region_name = self.synthesize_region_name(counter); @@ -229,9 +487,11 @@ impl<'tcx> RegionInferenceContext<'tcx> { counter: &mut usize, diag: &mut DiagnosticBuilder<'_>, ) -> Option { - let return_ty = self.universal_regions - .unnormalized_output_ty; - debug!("give_name_if_anonymous_region_appears_in_output: return_ty = {:?}", return_ty); + let return_ty = self.universal_regions.unnormalized_output_ty; + debug!( + "give_name_if_anonymous_region_appears_in_output: return_ty = {:?}", + return_ty + ); if !tcx.any_free_region_meets(&return_ty, |r| r.to_region_vid() == fr) { return None; } diff --git a/src/libsyntax/codemap.rs b/src/libsyntax/codemap.rs index ea6b39504e81d..8381adaea79de 100644 --- a/src/libsyntax/codemap.rs +++ b/src/libsyntax/codemap.rs @@ -689,6 +689,15 @@ impl CodeMap { self.span_until_char(sp, '{') } + /// Returns a new span representing just the start-point of this span + pub fn start_point(&self, sp: Span) -> Span { + let pos = sp.lo().0; + let width = self.find_width_of_character_at_span(sp, false); + let corrected_start_position = pos.checked_add(width).unwrap_or(pos); + let end_point = BytePos(cmp::max(corrected_start_position, sp.lo().0)); + sp.with_hi(end_point) + } + /// Returns a new span representing just the end-point of this span pub fn end_point(&self, sp: Span) -> Span { let pos = sp.hi().0; diff --git a/src/test/ui/borrowck/issue-7573.nll.stderr b/src/test/ui/borrowck/issue-7573.nll.stderr index daa0a320b88d6..5904e98753694 100644 --- a/src/test/ui/borrowck/issue-7573.nll.stderr +++ b/src/test/ui/borrowck/issue-7573.nll.stderr @@ -11,7 +11,7 @@ LL | let mut lines_to_use: Vec<&CrateId> = Vec::new(); | ---------------- lifetime `'2` appears in the type of `lines_to_use` LL | //~^ NOTE cannot infer an appropriate lifetime LL | let push_id = |installed_id: &CrateId| { - | ------------ lifetime `'1` appears in this argument + | - let's call the lifetime of this reference `'1` ... LL | lines_to_use.push(installed_id); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ argument requires that `'1` must outlive `'2` diff --git a/src/test/ui/closure-expected-type/expect-region-supply-region.nll.stderr b/src/test/ui/closure-expected-type/expect-region-supply-region.nll.stderr index 5487d34813b47..c8c8ef8215ae2 100644 --- a/src/test/ui/closure-expected-type/expect-region-supply-region.nll.stderr +++ b/src/test/ui/closure-expected-type/expect-region-supply-region.nll.stderr @@ -38,7 +38,7 @@ error: unsatisfied lifetime constraints LL | let mut f: Option<&u32> = None; | ----- lifetime `'2` appears in the type of `f` LL | closure_expecting_bound(|x: &u32| { - | - lifetime `'1` appears in this argument + | - let's call the lifetime of this reference `'1` LL | f = Some(x); //~ ERROR borrowed data cannot be stored outside of its closure | ^^^^^^^^^^^ free region requires that `'1` must outlive `'2` @@ -49,7 +49,7 @@ LL | let mut f: Option<&u32> = None; | ----- lifetime `'2` appears in the type of `f` ... LL | closure_expecting_bound(|x: &'x u32| { - | - lifetime `'1` appears in this argument + | - let's call the lifetime of this reference `'1` ... LL | f = Some(x); | ^^^^^^^^^^^ free region requires that `'1` must outlive `'2` diff --git a/src/test/ui/impl-trait/static-return-lifetime-infered.nll.stderr b/src/test/ui/impl-trait/static-return-lifetime-infered.nll.stderr index 9aad7efdee5b2..4c0b3a5d93120 100644 --- a/src/test/ui/impl-trait/static-return-lifetime-infered.nll.stderr +++ b/src/test/ui/impl-trait/static-return-lifetime-infered.nll.stderr @@ -14,7 +14,7 @@ error: unsatisfied lifetime constraints --> $DIR/static-return-lifetime-infered.rs:17:9 | LL | fn iter_values_anon(&self) -> impl Iterator { - | ----- lifetime `'1` appears in this argument + | - let's call the lifetime of this reference `'1` LL | self.x.iter().map(|a| a.0) | ^^^^^^ cast requires that `'1` must outlive `'static` diff --git a/src/test/ui/underscore-lifetime/dyn-trait-underscore.nll.stderr b/src/test/ui/underscore-lifetime/dyn-trait-underscore.nll.stderr index 04c3ed2d6ee19..6385578698cf7 100644 --- a/src/test/ui/underscore-lifetime/dyn-trait-underscore.nll.stderr +++ b/src/test/ui/underscore-lifetime/dyn-trait-underscore.nll.stderr @@ -26,7 +26,7 @@ error: unsatisfied lifetime constraints --> $DIR/dyn-trait-underscore.rs:18:5 | LL | fn a(items: &[T]) -> Box> { - | ----- lifetime `'1` appears in this argument + | - let's call the lifetime of this reference `'1` LL | // ^^^^^^^^^^^^^^^^^^^^^ bound *here* defaults to `'static` LL | Box::new(items.iter()) //~ ERROR cannot infer an appropriate lifetime | ^^^^^^^^^^^^^^^^^^^^^^ cast requires that `'1` must outlive `'static`