Fix issue rust-lang#125143

 - More than one unnamed lifetimes gave incorrect spans when lookup
   was done by name (since they both had name "'_"). Use DefId instead
   to get correct spans.

compiler/rustc_hir/src/hir.rs

@@ -571,6 +571,10 @@ impl<'hir> Generics<'hir> {
         self.params.iter().find(|&param| name == param.name.ident().name)
     }
 
+    pub fn get_with_def_id(&self, id: DefId) -> Option<&GenericParam<'hir>> {
+        self.params.iter().find(|&param| id.index == param.def_id.local_def_index)
+    }
+
     /// If there are generic parameters, return where to introduce a new one.
     pub fn span_for_lifetime_suggestion(&self) -> Option<Span> {
         if let Some(first) = self.params.first()

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -201,8 +201,10 @@ fn msg_span_from_named_region<'tcx>(
     match *region {
         ty::ReEarlyParam(ref br) => {
             let scope = region.free_region_binding_scope(tcx).expect_local();
-            let span = if let Some(param) =
-                tcx.hir().get_generics(scope).and_then(|generics| generics.get_named(br.name))
+            let span = if let Some(param) = tcx
+                .hir()
+                .get_generics(scope)
+                .and_then(|generics| generics.get_with_def_id(br.def_id))
             {
                 param.span
             } else {