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Use ocx.normalize in report_projection_error #104903

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merged 2 commits into from
Dec 3, 2022
Merged

Use ocx.normalize in report_projection_error #104903

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4dacf4f
Use ocx.normalize in report_projection_error
spastorino Nov 25, 2022
8904743
Define values and err as non mutable
spastorino Nov 30, 2022
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18 changes: 18 additions & 0 deletions compiler/rustc_trait_selection/src/traits/engine.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -112,6 +112,24 @@ impl<'a, 'tcx> ObligationCtxt<'a, 'tcx> {
self.register_infer_ok_obligations(infer_ok)
}

/// Makes `expected <: actual`.
pub fn eq_exp<T>(
&self,
cause: &ObligationCause<'tcx>,
param_env: ty::ParamEnv<'tcx>,
a_is_expected: bool,
a: T,
b: T,
) -> Result<(), TypeError<'tcx>>
where
T: ToTrace<'tcx>,
{
self.infcx
.at(cause, param_env)
.eq_exp(a_is_expected, a, b)
.map(|infer_ok| self.register_infer_ok_obligations(infer_ok))
}

pub fn eq<T: ToTrace<'tcx>>(
&self,
cause: &ObligationCause<'tcx>,
Expand Down
51 changes: 30 additions & 21 deletions compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1577,32 +1577,26 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
}

self.probe(|_| {
let mut err = error.err;
let mut values = None;
let ocx = ObligationCtxt::new_in_snapshot(self);

// try to find the mismatched types to report the error with.
//
// this can fail if the problem was higher-ranked, in which
// cause I have no idea for a good error message.
let bound_predicate = predicate.kind();
if let ty::PredicateKind::Clause(ty::Clause::Projection(data)) =
let (values, err) = if let ty::PredicateKind::Clause(ty::Clause::Projection(data)) =
bound_predicate.skip_binder()
{
let mut selcx = SelectionContext::new(self);
let data = self.replace_bound_vars_with_fresh_vars(
obligation.cause.span,
infer::LateBoundRegionConversionTime::HigherRankedType,
bound_predicate.rebind(data),
);
let mut obligations = vec![];
// FIXME(normalization): Change this to use `At::normalize`
let normalized_ty = super::normalize_projection_type(
&mut selcx,
let normalized_ty = ocx.normalize(
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&obligation.cause,
obligation.param_env,
data.projection_ty,
obligation.cause.clone(),
0,
&mut obligations,
self.tcx
.mk_projection(data.projection_ty.item_def_id, data.projection_ty.substs),
);

debug!(?obligation.cause, ?obligation.param_env);
Expand All @@ -1618,19 +1612,34 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
| ObligationCauseCode::ObjectCastObligation(..)
| ObligationCauseCode::OpaqueType
);
if let Err(new_err) = self.at(&obligation.cause, obligation.param_env).eq_exp(
let expected_ty = data.term.ty().unwrap();

// constrain inference variables a bit more to nested obligations from normalize so
// we can have more helpful errors.
ocx.select_where_possible();

if let Err(new_err) = ocx.eq_exp(
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&obligation.cause,
obligation.param_env,
is_normalized_ty_expected,
normalized_ty,
data.term,
expected_ty,
) {
values = Some((data, is_normalized_ty_expected, normalized_ty, data.term));
err = new_err;
(Some((data, is_normalized_ty_expected, normalized_ty, expected_ty)), new_err)
} else {
(None, error.err)
}
}
} else {
(None, error.err)
};

let msg = values
.and_then(|(predicate, _, normalized_ty, expected_ty)| {
self.maybe_detailed_projection_msg(predicate, normalized_ty, expected_ty)
self.maybe_detailed_projection_msg(
predicate,
normalized_ty.into(),
expected_ty.into(),
)
})
.unwrap_or_else(|| format!("type mismatch resolving `{}`", predicate));
let mut diag = struct_span_err!(self.tcx.sess, obligation.cause.span, E0271, "{msg}");
Expand Down Expand Up @@ -1672,11 +1681,11 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
&mut diag,
&obligation.cause,
secondary_span,
values.map(|(_, is_normalized_ty_expected, normalized_ty, term)| {
values.map(|(_, is_normalized_ty_expected, normalized_ty, expected_ty)| {
infer::ValuePairs::Terms(ExpectedFound::new(
is_normalized_ty_expected,
normalized_ty,
term,
normalized_ty.into(),
expected_ty.into(),
))
}),
err,
Expand Down