From 0ff8eeb308e1aa322cce35db125715cbaffc2341 Mon Sep 17 00:00:00 2001
From: Nathan Shively-Sanders <nathansa@microsoft.com>
Date: Wed, 23 Aug 2017 11:57:06 -0700
Subject: [PATCH] Comment getTypeReferenceId and getRelationKey

---
 src/compiler/checker.ts | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index e07ab5c7a28..272369df1ef 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -9774,6 +9774,10 @@ namespace ts {
             return getObjectFlags(type) & ObjectFlags.Reference && some((<TypeReference>type).typeArguments, isUnconstrainedTypeParameter);
         }
 
+        /**
+         * getTypeReferenceId(A<T, number, U>) returns "111=0-12=1"
+         *   where A.id=111 and number.id=12
+         */
         function getTypeReferenceId(type: TypeReference, typeParameters: Type[]) {
             let result = "" + type.target.id;
             for (const t of type.typeArguments) {
@@ -9792,6 +9796,10 @@ namespace ts {
             return result;
         }
 
+        /**
+         * To improve caching, the relation key for two generic types uses the target's id plus ids of the type parameters.
+         * For other cases, the types ids are used.
+         */
         function getRelationKey(source: Type, target: Type, relation: Map<RelationComparisonResult>) {
             if (relation === identityRelation && source.id > target.id) {
                 const temp = source;