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Don't ICE when ambiguity is found when selecting Index implementation in typeck

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This commit is contained in:
Michael Goulet 2023-11-20 23:35:20 +00:00
parent 46ecc10c69
commit 273dc22b04
3 changed files with 56 additions and 4 deletions
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22
compiler/rustc_hir_typeck/src/expr.rs
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@ -3064,7 +3064,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
return None;
};
self.commit_if_ok(|_| {
self.commit_if_ok(|snapshot| {
let outer_universe = self.universe();
let ocx = ObligationCtxt::new(self);
let impl_args = self.fresh_args_for_item(base_expr.span, impl_def_id);
let impl_trait_ref =
@ -3074,7 +3076,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
// Match the impl self type against the base ty. If this fails,
// we just skip this impl, since it's not particularly useful.
let impl_trait_ref = ocx.normalize(&cause, self.param_env, impl_trait_ref);
ocx.eq(&cause, self.param_env, impl_trait_ref.self_ty(), base_ty)?;
ocx.eq(&cause, self.param_env, base_ty, impl_trait_ref.self_ty())?;
// Register the impl's predicates. One of these predicates
// must be unsatisfied, or else we wouldn't have gotten here
@ -3110,11 +3112,23 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
Ty::new_projection(self.tcx, index_trait_output_def_id, impl_trait_ref.args),
);
let errors = ocx.select_where_possible();
let true_errors = ocx.select_where_possible();
// Do a leak check -- we can't really report report a useful error here,
// but it at least avoids an ICE when the error has to do with higher-ranked
// lifetimes.
self.leak_check(outer_universe, Some(snapshot))?;
// Bail if we have ambiguity errors, which we can't report in a useful way.
let ambiguity_errors = ocx.select_all_or_error();
if true_errors.is_empty() && !ambiguity_errors.is_empty() {
return Err(NoSolution);
}
// There should be at least one error reported. If not, we
// will still delay a span bug in `report_fulfillment_errors`.
Ok::<_, NoSolution>((
self.err_ctxt().report_fulfillment_errors(errors),
self.err_ctxt().report_fulfillment_errors(true_errors),
impl_trait_ref.args.type_at(1),
element_ty,
))