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Placeholder lifetime error cleanup #81972

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merged 7 commits into from
Feb 18, 2021
Merged

Placeholder lifetime error cleanup #81972

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1eb79f3
Use longer lifetime in `try_report_from_nll` return type
matthewjasper Feb 9, 2021
638980a
Using tracing macros in placeholder_error.rs
matthewjasper Feb 9, 2021
c2066cf
Remove unnecessary note on errors
matthewjasper Feb 9, 2021
daab6db
Avoid repeating self type in placeholder error
matthewjasper Feb 9, 2021
94c11df
Report "nice" placeholder errors more often
matthewjasper Feb 9, 2021
9337d4f
Print closure signatures when reporting placeholder errors
matthewjasper Feb 9, 2021
f852160
Keep existing names of regions in placeholder_error
matthewjasper Feb 10, 2021
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2 changes: 1 addition & 1 deletion compiler/rustc_infer/src/infer/error_reporting/nice_region_error/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -43,7 +43,7 @@ impl<'cx, 'tcx> NiceRegionError<'cx, 'tcx> {
self.infcx.tcx
}

pub fn try_report_from_nll(&self) -> Option<DiagnosticBuilder<'cx>> {
pub fn try_report_from_nll(&self) -> Option<DiagnosticBuilder<'tcx>> {
// Due to the improved diagnostics returned by the MIR borrow checker, only a subset of
// the nice region errors are required when running under the MIR borrow checker.
self.try_report_named_anon_conflict().or_else(|| self.try_report_placeholder_conflict())
Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_infer/src/infer/error_reporting/nice_region_error/named_anon_conflict.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,7 @@ use rustc_middle::ty;
impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
/// When given a `ConcreteFailure` for a function with parameters containing a named region and
/// an anonymous region, emit an descriptive diagnostic error.
pub(super) fn try_report_named_anon_conflict(&self) -> Option<DiagnosticBuilder<'a>> {
pub(super) fn try_report_named_anon_conflict(&self) -> Option<DiagnosticBuilder<'tcx>> {
let (span, sub, sup) = self.regions()?;

debug!(
Expand Down
232 changes: 126 additions & 106 deletions compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -16,7 +16,7 @@ use std::fmt::{self, Write};
impl NiceRegionError<'me, 'tcx> {
/// When given a `ConcreteFailure` for a function with arguments containing a named region and
/// an anonymous region, emit a descriptive diagnostic error.
pub(super) fn try_report_placeholder_conflict(&self) -> Option<DiagnosticBuilder<'me>> {
pub(super) fn try_report_placeholder_conflict(&self) -> Option<DiagnosticBuilder<'tcx>> {
match &self.error {
///////////////////////////////////////////////////////////////////////////
// NB. The ordering of cases in this match is very
Expand All @@ -30,157 +30,153 @@ impl NiceRegionError<'me, 'tcx> {
Some(RegionResolutionError::SubSupConflict(
vid,
_,
SubregionOrigin::Subtype(box TypeTrace {
cause,
values: ValuePairs::TraitRefs(ExpectedFound { expected, found }),
}),
SubregionOrigin::Subtype(box TypeTrace { cause, values }),
sub_placeholder @ ty::RePlaceholder(_),
_,
sup_placeholder @ ty::RePlaceholder(_),
)) if expected.def_id == found.def_id => Some(self.try_report_placeholders_trait(
)) => self.try_report_trait_placeholder_mismatch(
Some(self.tcx().mk_region(ty::ReVar(*vid))),
cause,
Some(sub_placeholder),
Some(sup_placeholder),
expected.def_id,
expected.substs,
found.substs,
)),
values,
),

Some(RegionResolutionError::SubSupConflict(
vid,
_,
SubregionOrigin::Subtype(box TypeTrace {
cause,
values: ValuePairs::TraitRefs(ExpectedFound { expected, found }),
}),
SubregionOrigin::Subtype(box TypeTrace { cause, values }),
sub_placeholder @ ty::RePlaceholder(_),
_,
_,
)) if expected.def_id == found.def_id => Some(self.try_report_placeholders_trait(
)) => self.try_report_trait_placeholder_mismatch(
Some(self.tcx().mk_region(ty::ReVar(*vid))),
cause,
Some(sub_placeholder),
None,
expected.def_id,
expected.substs,
found.substs,
)),
values,
),

Some(RegionResolutionError::SubSupConflict(
vid,
_,
SubregionOrigin::Subtype(box TypeTrace {
cause,
values: ValuePairs::TraitRefs(ExpectedFound { expected, found }),
}),
SubregionOrigin::Subtype(box TypeTrace { cause, values }),
_,
_,
sup_placeholder @ ty::RePlaceholder(_),
)) if expected.def_id == found.def_id => Some(self.try_report_placeholders_trait(
)) => self.try_report_trait_placeholder_mismatch(
Some(self.tcx().mk_region(ty::ReVar(*vid))),
cause,
None,
Some(*sup_placeholder),
expected.def_id,
expected.substs,
found.substs,
)),
values,
),

Some(RegionResolutionError::SubSupConflict(
vid,
_,
_,
_,
SubregionOrigin::Subtype(box TypeTrace {
cause,
values: ValuePairs::TraitRefs(ExpectedFound { expected, found }),
}),
SubregionOrigin::Subtype(box TypeTrace { cause, values }),
sup_placeholder @ ty::RePlaceholder(_),
)) if expected.def_id == found.def_id => Some(self.try_report_placeholders_trait(
)) => self.try_report_trait_placeholder_mismatch(
Some(self.tcx().mk_region(ty::ReVar(*vid))),
cause,
None,
Some(*sup_placeholder),
expected.def_id,
expected.substs,
found.substs,
)),
values,
),

Some(RegionResolutionError::UpperBoundUniverseConflict(
vid,
_,
_,
SubregionOrigin::Subtype(box TypeTrace {
cause,
values: ValuePairs::TraitRefs(ExpectedFound { expected, found }),
}),
SubregionOrigin::Subtype(box TypeTrace { cause, values }),
sup_placeholder @ ty::RePlaceholder(_),
)) if expected.def_id == found.def_id => Some(self.try_report_placeholders_trait(
)) => self.try_report_trait_placeholder_mismatch(
Some(self.tcx().mk_region(ty::ReVar(*vid))),
cause,
None,
Some(*sup_placeholder),
expected.def_id,
expected.substs,
found.substs,
)),
values,
),

Some(RegionResolutionError::ConcreteFailure(
SubregionOrigin::Subtype(box TypeTrace {
cause,
values: ValuePairs::TraitRefs(ExpectedFound { expected, found }),
}),
SubregionOrigin::Subtype(box TypeTrace { cause, values }),
sub_region @ ty::RePlaceholder(_),
sup_region @ ty::RePlaceholder(_),
)) if expected.def_id == found.def_id => Some(self.try_report_placeholders_trait(
)) => self.try_report_trait_placeholder_mismatch(
None,
cause,
Some(*sub_region),
Some(*sup_region),
expected.def_id,
expected.substs,
found.substs,
)),
values,
),

Some(RegionResolutionError::ConcreteFailure(
SubregionOrigin::Subtype(box TypeTrace {
cause,
values: ValuePairs::TraitRefs(ExpectedFound { expected, found }),
}),
SubregionOrigin::Subtype(box TypeTrace { cause, values }),
sub_region @ ty::RePlaceholder(_),
sup_region,
)) if expected.def_id == found.def_id => Some(self.try_report_placeholders_trait(
Some(sup_region),
)) => self.try_report_trait_placeholder_mismatch(
(!sup_region.has_name()).then_some(sup_region),
cause,
Some(*sub_region),
Some(sub_region),
None,
expected.def_id,
expected.substs,
found.substs,
)),
values,
),

Some(RegionResolutionError::ConcreteFailure(
SubregionOrigin::Subtype(box TypeTrace {
cause,
values: ValuePairs::TraitRefs(ExpectedFound { expected, found }),
}),
SubregionOrigin::Subtype(box TypeTrace { cause, values }),
sub_region,
sup_region @ ty::RePlaceholder(_),
)) if expected.def_id == found.def_id => Some(self.try_report_placeholders_trait(
Some(sub_region),
)) => self.try_report_trait_placeholder_mismatch(
(!sub_region.has_name()).then_some(sub_region),
cause,
None,
Some(*sup_region),
expected.def_id,
expected.substs,
found.substs,
)),
Some(sup_region),
values,
),

_ => None,
}
}

fn try_report_trait_placeholder_mismatch(
&self,
vid: Option<ty::Region<'tcx>>,
cause: &ObligationCause<'tcx>,
sub_placeholder: Option<ty::Region<'tcx>>,
sup_placeholder: Option<ty::Region<'tcx>>,
value_pairs: &ValuePairs<'tcx>,
) -> Option<DiagnosticBuilder<'tcx>> {
let (expected_substs, found_substs, trait_def_id) = match value_pairs {
ValuePairs::TraitRefs(ExpectedFound { expected, found })
if expected.def_id == found.def_id =>
{
(expected.substs, found.substs, expected.def_id)
}
ValuePairs::PolyTraitRefs(ExpectedFound { expected, found })
if expected.def_id() == found.def_id() =>
{
// It's possible that the placeholders come from a binder
// outside of this value pair. Use `no_bound_vars` as a
// simple heuristic for that.
(expected.no_bound_vars()?.substs, found.no_bound_vars()?.substs, expected.def_id())
}
_ => return None,
};

Some(self.report_trait_placeholder_mismatch(
vid,
cause,
sub_placeholder,
sup_placeholder,
trait_def_id,
expected_substs,
found_substs,
))
}

// error[E0308]: implementation of `Foo` does not apply to enough lifetimes
// --> /home/nmatsakis/tmp/foo.rs:12:5
// |
Expand All @@ -190,7 +186,8 @@ impl NiceRegionError<'me, 'tcx> {
// = note: Due to a where-clause on the function `all`,
// = note: `T` must implement `...` for any two lifetimes `'1` and `'2`.
// = note: However, the type `T` only implements `...` for some specific lifetime `'2`.
fn try_report_placeholders_trait(
#[instrument(level = "debug", skip(self))]
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ths is so nice!

fn report_trait_placeholder_mismatch(
&self,
vid: Option<ty::Region<'tcx>>,
cause: &ObligationCause<'tcx>,
Expand All @@ -199,28 +196,13 @@ impl NiceRegionError<'me, 'tcx> {
trait_def_id: DefId,
expected_substs: SubstsRef<'tcx>,
actual_substs: SubstsRef<'tcx>,
) -> DiagnosticBuilder<'me> {
debug!(
"try_report_placeholders_trait(\
vid={:?}, \
sub_placeholder={:?}, \
sup_placeholder={:?}, \
trait_def_id={:?}, \
expected_substs={:?}, \
actual_substs={:?})",
vid, sub_placeholder, sup_placeholder, trait_def_id, expected_substs, actual_substs
);

) -> DiagnosticBuilder<'tcx> {
let span = cause.span(self.tcx());
let msg = format!(
"implementation of `{}` is not general enough",
self.tcx().def_path_str(trait_def_id),
);
let mut err = self.tcx().sess.struct_span_err(span, &msg);
err.span_label(
self.tcx().def_span(trait_def_id),
format!("trait `{}` defined here", self.tcx().def_path_str(trait_def_id)),
);

let leading_ellipsis = if let ObligationCauseCode::ItemObligation(def_id) = cause.code {
err.span_label(span, "doesn't satisfy where-clause");
Expand Down Expand Up @@ -285,17 +267,13 @@ impl NiceRegionError<'me, 'tcx> {

let any_self_ty_has_vid = actual_self_ty_has_vid || expected_self_ty_has_vid;

debug!("try_report_placeholders_trait: actual_has_vid={:?}", actual_has_vid);
debug!("try_report_placeholders_trait: expected_has_vid={:?}", expected_has_vid);
debug!("try_report_placeholders_trait: has_sub={:?}", has_sub);
debug!("try_report_placeholders_trait: has_sup={:?}", has_sup);
debug!(
"try_report_placeholders_trait: actual_self_ty_has_vid={:?}",
actual_self_ty_has_vid
);
debug!(
"try_report_placeholders_trait: expected_self_ty_has_vid={:?}",
expected_self_ty_has_vid
?actual_has_vid,
?expected_has_vid,
?has_sub,
?has_sup,
?actual_self_ty_has_vid,
?expected_self_ty_has_vid,
);

self.explain_actual_impl_that_was_found(
Expand Down Expand Up @@ -388,6 +366,8 @@ impl NiceRegionError<'me, 'tcx> {
value: trait_ref,
};

let same_self_type = actual_trait_ref.self_ty() == expected_trait_ref.self_ty();

let mut expected_trait_ref = highlight_trait_ref(expected_trait_ref);
expected_trait_ref.highlight.maybe_highlighting_region(sub_placeholder, has_sub);
expected_trait_ref.highlight.maybe_highlighting_region(sup_placeholder, has_sup);
Expand All @@ -403,7 +383,42 @@ impl NiceRegionError<'me, 'tcx> {
}
};

let mut note = if passive_voice {
let mut note = if same_self_type {
let mut self_ty = expected_trait_ref.map(|tr| tr.self_ty());
self_ty.highlight.maybe_highlighting_region(vid, actual_has_vid);

if self_ty.value.is_closure()
&& self
.tcx()
.fn_trait_kind_from_lang_item(expected_trait_ref.value.def_id)
.is_some()
{
let closure_sig = self_ty.map(|closure| {
if let ty::Closure(_, substs) = closure.kind() {
self.tcx().signature_unclosure(
substs.as_closure().sig(),
rustc_hir::Unsafety::Normal,
)
} else {
bug!("type is not longer closure");
}
});

format!(
"{}closure with signature `{}` must implement `{}`",
if leading_ellipsis { "..." } else { "" },
closure_sig,
expected_trait_ref.map(|tr| tr.print_only_trait_path()),
)
} else {
format!(
"{}`{}` must implement `{}`",
if leading_ellipsis { "..." } else { "" },
self_ty,
expected_trait_ref.map(|tr| tr.print_only_trait_path()),
)
}
} else if passive_voice {
format!(
"{}`{}` would have to be implemented for the type `{}`",
if leading_ellipsis { "..." } else { "" },
Expand Down Expand Up @@ -449,7 +464,12 @@ impl NiceRegionError<'me, 'tcx> {
None => true,
};

let mut note = if passive_voice {
let mut note = if same_self_type {
format!(
"...but it actually implements `{}`",
actual_trait_ref.map(|tr| tr.print_only_trait_path()),
)
} else if passive_voice {
format!(
"...but `{}` is actually implemented for the type `{}`",
actual_trait_ref.map(|tr| tr.print_only_trait_path()),
Expand Down
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