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Rollup merge of rust-lang#64151 - estebank:binding-error, r=varkor
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On obligation errors point at the unfulfilled binding when possible

CC rust-lang#42855, rust-lang#64130, rust-lang#64135.
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Centril authored Sep 19, 2019

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2 parents f4f16cd + 829c3c3 commit e314d39
Showing 171 changed files with 714 additions and 610 deletions.
2 changes: 2 additions & 0 deletions src/etc/generate-deriving-span-tests.py
Original file line number Diff line number Diff line change
@@ -14,6 +14,8 @@
os.path.join(os.path.dirname(__file__), '../test/ui/derives/'))

TEMPLATE = """\
// ignore-musl
// ^ due to stderr output differences
// This file was auto-generated using 'src/etc/generate-deriving-span-tests.py'
{error_deriving}
5 changes: 4 additions & 1 deletion src/librustc/hir/lowering.rs
Original file line number Diff line number Diff line change
@@ -1893,10 +1893,13 @@ impl<'a> LoweringContext<'a> {
if let Ok(snippet) = self.sess.source_map().span_to_snippet(data.span) {
// Do not suggest going from `Trait()` to `Trait<>`
if data.inputs.len() > 0 {
let split = snippet.find('(').unwrap();
let trait_name = &snippet[0..split];
let args = &snippet[split + 1 .. snippet.len() - 1];
err.span_suggestion(
data.span,
"use angle brackets instead",
format!("<{}>", &snippet[1..snippet.len() - 1]),
format!("{}<{}>", trait_name, args),
Applicability::MaybeIncorrect,
);
}
12 changes: 12 additions & 0 deletions src/librustc/hir/mod.rs
Original file line number Diff line number Diff line change
@@ -2750,3 +2750,15 @@ pub enum Node<'hir> {

Crate,
}

impl Node<'_> {
pub fn ident(&self) -> Option<Ident> {
match self {
Node::TraitItem(TraitItem { ident, .. }) |
Node::ImplItem(ImplItem { ident, .. }) |
Node::ForeignItem(ForeignItem { ident, .. }) |
Node::Item(Item { ident, .. }) => Some(*ident),
_ => None,
}
}
}
22 changes: 18 additions & 4 deletions src/librustc/traits/error_reporting.rs
Original file line number Diff line number Diff line change
@@ -40,10 +40,12 @@ use syntax::symbol::{sym, kw};
use syntax_pos::{DUMMY_SP, Span, ExpnKind};

impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
pub fn report_fulfillment_errors(&self,
errors: &[FulfillmentError<'tcx>],
body_id: Option<hir::BodyId>,
fallback_has_occurred: bool) {
pub fn report_fulfillment_errors(
&self,
errors: &[FulfillmentError<'tcx>],
body_id: Option<hir::BodyId>,
fallback_has_occurred: bool,
) {
#[derive(Debug)]
struct ErrorDescriptor<'tcx> {
predicate: ty::Predicate<'tcx>,
@@ -1623,6 +1625,18 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
err.note(&msg);
}
}
ObligationCauseCode::BindingObligation(item_def_id, span) => {
let item_name = tcx.def_path_str(item_def_id);
let msg = format!("required by this bound in `{}`", item_name);
if let Some(ident) = tcx.opt_item_name(item_def_id) {
err.span_label(ident.span, "");
}
if span != DUMMY_SP {
err.span_label(span, &msg);
} else {
err.note(&msg);
}
}
ObligationCauseCode::ObjectCastObligation(object_ty) => {
err.note(&format!("required for the cast to the object type `{}`",
self.ty_to_string(object_ty)));
3 changes: 3 additions & 0 deletions src/librustc/traits/mod.rs
Original file line number Diff line number Diff line change
@@ -176,6 +176,9 @@ pub enum ObligationCauseCode<'tcx> {
/// also implement all supertraits of `X`.
ItemObligation(DefId),

/// Like `ItemObligation`, but with extra detail on the source of the obligation.
BindingObligation(DefId, Span),

/// A type like `&'a T` is WF only if `T: 'a`.
ReferenceOutlivesReferent(Ty<'tcx>),

1 change: 1 addition & 0 deletions src/librustc/traits/structural_impls.rs
Original file line number Diff line number Diff line change
@@ -472,6 +472,7 @@ impl<'a, 'tcx> Lift<'tcx> for traits::ObligationCauseCode<'a> {
super::TupleElem => Some(super::TupleElem),
super::ProjectionWf(proj) => tcx.lift(&proj).map(super::ProjectionWf),
super::ItemObligation(def_id) => Some(super::ItemObligation(def_id)),
super::BindingObligation(def_id, span) => Some(super::BindingObligation(def_id, span)),
super::ReferenceOutlivesReferent(ty) => {
tcx.lift(&ty).map(super::ReferenceOutlivesReferent)
}
4 changes: 4 additions & 0 deletions src/librustc/ty/mod.rs
Original file line number Diff line number Diff line change
@@ -2797,6 +2797,10 @@ impl<'tcx> TyCtxt<'tcx> {
})
}

pub fn opt_item_name(self, def_id: DefId) -> Option<Ident> {
self.hir().as_local_hir_id(def_id).and_then(|hir_id| self.hir().get(hir_id).ident())
}

pub fn opt_associated_item(self, def_id: DefId) -> Option<AssocItem> {
let is_associated_item = if let Some(hir_id) = self.hir().as_local_hir_id(def_id) {
match self.hir().get(hir_id) {
52 changes: 38 additions & 14 deletions src/librustc_typeck/check/mod.rs
Original file line number Diff line number Diff line change
@@ -2579,16 +2579,24 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {

/// As `instantiate_type_scheme`, but for the bounds found in a
/// generic type scheme.
fn instantiate_bounds(&self, span: Span, def_id: DefId, substs: SubstsRef<'tcx>)
-> ty::InstantiatedPredicates<'tcx> {
fn instantiate_bounds(
&self,
span: Span,
def_id: DefId,
substs: SubstsRef<'tcx>,
) -> (ty::InstantiatedPredicates<'tcx>, Vec<Span>) {
let bounds = self.tcx.predicates_of(def_id);
let spans: Vec<Span> = bounds.predicates.iter().map(|(_, span)| *span).collect();
let result = bounds.instantiate(self.tcx, substs);
let result = self.normalize_associated_types_in(span, &result);
debug!("instantiate_bounds(bounds={:?}, substs={:?}) = {:?}",
debug!(
"instantiate_bounds(bounds={:?}, substs={:?}) = {:?}, {:?}",
bounds,
substs,
result);
result
result,
spans,
);
(result, spans)
}

/// Replaces the opaque types from the given value with type variables,
@@ -3151,8 +3159,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {

// All the input types from the fn signature must outlive the call
// so as to validate implied bounds.
for &fn_input_ty in fn_inputs {
self.register_wf_obligation(fn_input_ty, sp, traits::MiscObligation);
for (fn_input_ty, arg_expr) in fn_inputs.iter().zip(args.iter()) {
self.register_wf_obligation(fn_input_ty, arg_expr.span, traits::MiscObligation);
}

let expected_arg_count = fn_inputs.len();
@@ -3513,7 +3521,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
self.write_user_type_annotation_from_substs(hir_id, did, substs, None);

// Check bounds on type arguments used in the path.
let bounds = self.instantiate_bounds(path_span, did, substs);
let (bounds, _) = self.instantiate_bounds(path_span, did, substs);
let cause = traits::ObligationCause::new(path_span, self.body_id,
traits::ItemObligation(did));
self.add_obligations_for_parameters(cause, &bounds);
@@ -4634,12 +4642,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
// First, store the "user substs" for later.
self.write_user_type_annotation_from_substs(hir_id, def_id, substs, user_self_ty);

// Add all the obligations that are required, substituting and
// normalized appropriately.
let bounds = self.instantiate_bounds(span, def_id, &substs);
self.add_obligations_for_parameters(
traits::ObligationCause::new(span, self.body_id, traits::ItemObligation(def_id)),
&bounds);
self.add_required_obligations(span, def_id, &substs);

// Substitute the values for the type parameters into the type of
// the referenced item.
@@ -4676,6 +4679,27 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
(ty_substituted, res)
}

/// Add all the obligations that are required, substituting and normalized appropriately.
fn add_required_obligations(&self, span: Span, def_id: DefId, substs: &SubstsRef<'tcx>) {
let (bounds, spans) = self.instantiate_bounds(span, def_id, &substs);

for (i, mut obligation) in traits::predicates_for_generics(
traits::ObligationCause::new(
span,
self.body_id,
traits::ItemObligation(def_id),
),
self.param_env,
&bounds,
).into_iter().enumerate() {
// This makes the error point at the bound, but we want to point at the argument
if let Some(span) = spans.get(i) {
obligation.cause.code = traits::BindingObligation(def_id, *span);
}
self.register_predicate(obligation);
}
}

fn check_rustc_args_require_const(&self,
def_id: DefId,
hir_id: hir::HirId,
11 changes: 6 additions & 5 deletions src/libsyntax/parse/parser/path.rs
Original file line number Diff line number Diff line change
@@ -129,10 +129,11 @@ impl<'a> Parser<'a> {
self.parse_path(style)
}

crate fn parse_path_segments(&mut self,
segments: &mut Vec<PathSegment>,
style: PathStyle)
-> PResult<'a, ()> {
crate fn parse_path_segments(
&mut self,
segments: &mut Vec<PathSegment>,
style: PathStyle,
) -> PResult<'a, ()> {
loop {
let segment = self.parse_path_segment(style)?;
if style == PathStyle::Expr {
@@ -201,7 +202,7 @@ impl<'a> Parser<'a> {
} else {
// `(T, U) -> R`
let (inputs, _) = self.parse_paren_comma_seq(|p| p.parse_ty())?;
let span = lo.to(self.prev_span);
let span = ident.span.to(self.prev_span);
let output = if self.eat(&token::RArrow) {
Some(self.parse_ty_common(false, false, false)?)
} else {
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