bjoernager/rust
bjoernager/rust
1
Fork 0
Code Issues Pull requests Activity

Improve cause information for NLL higher-ranked errors

Browse source 
This PR has several interconnected pieces:

1. In some of the NLL region error code, we now pass
   around an `ObligationCause`, instead of just a plain `Span`.
   This gets forwarded into `fulfill_cx.register_predicate_obligation`
   during error reporting.
2. The general InferCtxt error reporting code is extended to
   handle `ObligationCauseCode::BindingObligation`
3. A new enum variant `ConstraintCategory::Predicate` is added.
   We try to avoid using this as the 'best blame constraint' - instead,
   we use it to enhance the `ObligationCause` of the `BlameConstraint`
   that we do end up choosing.

As a result, several NLL error messages now contain the same
"the lifetime requirement is introduced here" message as non-NLL
errors.

Having an `ObligationCause` available will likely prove useful
for future improvements to NLL error messages.
This commit is contained in:
Aaron Hill 2021-08-28 18:45:37 -05:00
parent 3e8f32e1c5
commit 93ab12eeab
No known key found for this signature in database
GPG key ID: B4087E510E98B164
16 changed files with 194 additions and 82 deletions
Download patch file Download diff file Expand all files Collapse all files

18
compiler/rustc_borrowck/src/diagnostics/region_errors.rs
View file

@ -13,6 +13,7 @@ use rustc_span::{BytePos, Span};
use crate::borrowck_errors;
use super::{OutlivesSuggestionBuilder, RegionName};
use crate::region_infer::BlameConstraint;
use crate::{
nll::ConstraintDescription,
@ -21,8 +22,6 @@ use crate::{
MirBorrowckCtxt,
};
use super::{OutlivesSuggestionBuilder, RegionName};
impl ConstraintDescription for ConstraintCategory {
fn description(&self) -> &'static str {
// Must end with a space. Allows for empty names to be provided.
@ -41,7 +40,8 @@ impl ConstraintDescription for ConstraintCategory {
ConstraintCategory::OpaqueType => "opaque type ",
ConstraintCategory::ClosureUpvar(_) => "closure capture ",
ConstraintCategory::Usage => "this usage ",
ConstraintCategory::Boring
ConstraintCategory::Predicate(_, _)
| ConstraintCategory::Boring
| ConstraintCategory::BoringNoLocation
| ConstraintCategory::Internal => "",
}
@ -217,7 +217,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
let error_vid = self.regioncx.region_from_element(longer_fr, &error_element);
// Find the code to blame for the fact that `longer_fr` outlives `error_fr`.
let (_, span) = self.regioncx.find_outlives_blame_span(
let (_, cause) = self.regioncx.find_outlives_blame_span(
&self.body,
longer_fr,
NllRegionVariableOrigin::Placeholder(placeholder),
@ -227,7 +227,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
let universe = placeholder.universe;
let universe_info = self.regioncx.universe_info(universe);
universe_info.report_error(self, placeholder, error_element, span);
universe_info.report_error(self, placeholder, error_element, cause);
}
RegionErrorKind::RegionError { fr_origin, longer_fr, shorter_fr, is_reported } => {
@ -275,15 +275,15 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
) {
debug!("report_region_error(fr={:?}, outlived_fr={:?})", fr, outlived_fr);
let BlameConstraint { category, span, variance_info, from_closure: _ } =
let BlameConstraint { category, cause, variance_info, from_closure: _ } =
self.regioncx.best_blame_constraint(&self.body, fr, fr_origin, |r| {
self.regioncx.provides_universal_region(r, fr, outlived_fr)
});
debug!("report_region_error: category={:?} {:?} {:?}", category, span, variance_info);
debug!("report_region_error: category={:?} {:?} {:?}", category, cause, variance_info);
// Check if we can use one of the "nice region errors".
if let (Some(f), Some(o)) = (self.to_error_region(fr), self.to_error_region(outlived_fr)) {
let nice = NiceRegionError::new_from_span(self.infcx, span, o, f);
let nice = NiceRegionError::new_from_span(self.infcx, cause.span, o, f);
if let Some(diag) = nice.try_report_from_nll() {
diag.buffer(&mut self.errors_buffer);
return;
@ -306,7 +306,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
fr_is_local,
outlived_fr_is_local,
category,
span,
span: cause.span,
};
let mut diag = match (category, fr_is_local, outlived_fr_is_local) {