finish RegionKind rename

- `ReFree` -> `ReLateParam`
- `ReEarlyBound` -> `ReEarlyParam`

compiler/rustc_infer/src/errors/note_and_explain.rs

@@ -17,7 +17,7 @@ impl<'a> DescriptionCtx<'a> {
         alt_span: Option<Span>,
     ) -> Option<Self> {
         let (span, kind, arg) = match *region {
-            ty::ReEarlyBound(ref br) => {
+            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))
@@ -32,7 +32,7 @@ impl<'a> DescriptionCtx<'a> {
                     (Some(span), "as_defined_anon", String::new())
                 }
             }
-            ty::ReFree(ref fr) => {
+            ty::ReLateParam(ref fr) => {
                 if !fr.bound_region.is_named()
                     && let Some((ty, _)) = find_anon_type(tcx, region, &fr.bound_region)
                 {
@@ -70,7 +70,7 @@ impl<'a> DescriptionCtx<'a> {
             ty::RePlaceholder(_) | ty::ReError(_) => return None,
 
             // FIXME(#13998) RePlaceholder should probably print like
-            // ReFree rather than dumping Debug output on the user.
+            // ReLateParam rather than dumping Debug output on the user.
             //
             // We shouldn't really be having unification failures with ReVar
             // and ReBound though.