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Explain redundant mapping.

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This commit is contained in:
Camille GILLOT
2022-10-24 17:15:42 +00:00
parent b77674d254
commit 94234065cf
1 changed files with 4 additions and 0 deletions
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4
compiler/rustc_middle/src/ty/mod.rs
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@@ -1332,6 +1332,10 @@ impl<'tcx> OpaqueHiddenType<'tcx> {
let id_substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id()); let id_substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id());
debug!(?id_substs); debug!(?id_substs);
// This zip may have several times the same lifetime in `substs` paired with a different
// lifetime from `id_substs`. In that case, we actually want to pick the last one, as it
// is the one we introduced in the impl-trait desugaring to be meaningful. The other ones
// are redundant.
let map = substs.iter().zip(id_substs); let map = substs.iter().zip(id_substs);
let map: FxHashMap<GenericArg<'tcx>, GenericArg<'tcx>> = match origin { let map: FxHashMap<GenericArg<'tcx>, GenericArg<'tcx>> = match origin {