@@ -2089,13 +2089,19 @@ fn lint_redundant_lifetimes<'tcx>(
20892089 let mut shadowed = FxHashSet :: default ( ) ;
20902090
20912091 for ( idx, & candidate) in lifetimes. iter ( ) . enumerate ( ) {
2092- // Don't suggest removing a lifetime twice.
2092+ // Don't suggest removing a lifetime twice. We only need to check this
2093+ // here and not up in the `victim` loop because equality is transitive,
2094+ // so if A = C and B = C, then A must = B, so it'll be shadowed too in
2095+ // A's victim loop.
20932096 if shadowed. contains ( & candidate) {
20942097 continue ;
20952098 }
20962099
20972100 for & victim in & lifetimes[ ( idx + 1 ) ..] {
2098- // We only care about lifetimes that are "real", i.e. that have a def-id.
2101+ // We should only have late-bound lifetimes of the `BrNamed` variety,
2102+ // since we get these signatures straight from `hir_lowering`. And any
2103+ // other regions (ReError/ReStatic/etc.) shouldn't matter, since we
2104+ // can't really suggest to remove them.
20992105 let ( ty:: ReEarlyParam ( ty:: EarlyParamRegion { def_id, .. } )
21002106 | ty:: ReLateParam ( ty:: LateParamRegion {
21012107 bound_region : ty:: BoundRegionKind :: BrNamed ( def_id, _) ,
@@ -2113,7 +2119,7 @@ fn lint_redundant_lifetimes<'tcx>(
21132119 continue ;
21142120 }
21152121
2116- // If there are no lifetime errors, then we have proven that `' candidate = 'victim`!
2122+ // If `candidate <: victim` and `victim <: candidate`, then they're equal.
21172123 if outlives_env. free_region_map ( ) . sub_free_regions ( tcx, candidate, victim)
21182124 && outlives_env. free_region_map ( ) . sub_free_regions ( tcx, victim, candidate)
21192125 {
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