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Do not initiate nested probe within assemble_probe.

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In particular, the table entries (associated with type-variables
created during the probe) must persist as long as the candidates
assembled during the probe. If you make a nested probe without
creating a nested `ProbeContext`, the table entries are popped at the
end of the nested probe, while the type-variables would leak out via
the assembled candidates attached to `self` (the outer
`ProbeContext`). This causes an ICE (*if you are lucky*)!
This commit is contained in:
Felix S. Klock II 2019-01-22 13:51:30 +01:00
parent 38650b69ca
commit 2dea8ec630
1 changed files with 7 additions and 9 deletions
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16
src/librustc_typeck/check/method/probe.rs
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@ -506,15 +506,13 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
match self_ty.value.value.sty {
ty::Dynamic(ref data, ..) => {
if let Some(p) = data.principal() {
self.fcx.probe(|_| {
let InferOk { value: self_ty, obligations: _ } =
self.fcx.probe_instantiate_query_response(
self.span, &self.orig_steps_var_values, self_ty)
.unwrap_or_else(|_| {
span_bug!(self.span, "{:?} was applicable but now isn't?", self_ty)
});
self.assemble_inherent_candidates_from_object(self_ty);
});
let InferOk { value: instantiated_self_ty, obligations: _ } =
self.fcx.probe_instantiate_query_response(
self.span, &self.orig_steps_var_values, self_ty)
.unwrap_or_else(|_| {
span_bug!(self.span, "{:?} was applicable but now isn't?", self_ty)
});
self.assemble_inherent_candidates_from_object(instantiated_self_ty);
self.assemble_inherent_impl_candidates_for_type(p.def_id());
}
}