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Auto merge of #91030 - estebank:trait-bounds-are-tricky-2, r=oli-obk

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Properly track `ImplObligations`

Instead of probing for all possible `impl`s that could have caused an
`ImplObligation`, keep track of its `DefId` and obligation spans for
accurate error reporting.

Follow to #89580. Addresses #89418.
This commit is contained in:
bors 2022-03-24 10:24:54 +00:00
commit d2df372bca
24 changed files with 426 additions and 218 deletions
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27
compiler/rustc_middle/src/traits/mod.rs
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@ -257,7 +257,7 @@ pub enum ObligationCauseCode<'tcx> {
BuiltinDerivedObligation(DerivedObligationCause<'tcx>),
ImplDerivedObligation(DerivedObligationCause<'tcx>),
ImplDerivedObligation(Box<ImplDerivedObligationCause<'tcx>>),
DerivedObligation(DerivedObligationCause<'tcx>),
@ -396,16 +396,29 @@ pub enum WellFormedLoc {
},
}
#[derive(Clone, Debug, PartialEq, Eq, Hash, Lift)]
pub struct ImplDerivedObligationCause<'tcx> {
pub derived: DerivedObligationCause<'tcx>,
pub impl_def_id: DefId,
pub span: Span,
}
impl ObligationCauseCode<'_> {
// Return the base obligation, ignoring derived obligations.
pub fn peel_derives(&self) -> &Self {
let mut base_cause = self;
while let BuiltinDerivedObligation(DerivedObligationCause { parent_code, .. })
| ImplDerivedObligation(DerivedObligationCause { parent_code, .. })
| DerivedObligation(DerivedObligationCause { parent_code, .. })
| FunctionArgumentObligation { parent_code, .. } = base_cause
{
base_cause = &parent_code;
loop {
match base_cause {
BuiltinDerivedObligation(DerivedObligationCause { parent_code, .. })
| DerivedObligation(DerivedObligationCause { parent_code, .. })
| FunctionArgumentObligation { parent_code, .. } => {
base_cause = &parent_code;
}
ImplDerivedObligation(obligation_cause) => {
base_cause = &*obligation_cause.derived.parent_code;
}
_ => break,
}
}
base_cause
}