From 0037cca2f79c63143e3849ec84eebdaf4b451712 Mon Sep 17 00:00:00 2001
From: Niko Matsakis <niko@alum.mit.edu>
Date: Fri, 9 Feb 2018 10:43:36 -0500
Subject: [PATCH] comment the purpose of `TransNormalize`

---
 src/librustc/infer/mod.rs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/librustc/infer/mod.rs b/src/librustc/infer/mod.rs
index d952e430f61..713cf560851 100644
--- a/src/librustc/infer/mod.rs
+++ b/src/librustc/infer/mod.rs
@@ -487,6 +487,10 @@ pub struct CombinedSnapshot<'a, 'tcx:'a> {
 
 /// Helper trait for shortening the lifetimes inside a
 /// value for post-type-checking normalization.
+///
+/// This trait offers a normalization method where the inputs and
+/// outputs both have the `'gcx` lifetime; the implementations
+/// internally create inference contexts and/or lift as needed.
 pub trait TransNormalize<'gcx>: TypeFoldable<'gcx> {
     fn trans_normalize<'a, 'tcx>(&self,
                                  infcx: &InferCtxt<'a, 'gcx, 'tcx>,