microsoft
diff --git a/‎src/compiler/checker.ts‎
Lines changed: 5 additions & 1 deletion b/‎src/compiler/checker.ts‎
Lines changed: 5 additions & 1 deletion
diff --git a/‎src/compiler/types.ts‎
Lines changed: 2 additions & 0 deletions b/‎src/compiler/types.ts‎
Lines changed: 2 additions & 0 deletions
@@ -13457,9 +13457,13 @@ namespace ts {
             return type;
         }
 
+        function getRegularTypeOfUnion(type: UnionType) {
+            return type.regularType || (type.regularType = getUnionType(sameMap((<UnionType>type).types, getRegularTypeOfLiteralType)) as UnionType);
+        }
+
         function getRegularTypeOfLiteralType(type: Type): Type {
             return type.flags & TypeFlags.Literal ? (<LiteralType>type).regularType :
-                type.flags & TypeFlags.Union ? getUnionType(sameMap((<UnionType>type).types, getRegularTypeOfLiteralType)) :
+                type.flags & TypeFlags.Union ? getRegularTypeOfUnion(<UnionType>type) :
                 type;
         }
 
 
@@ -4651,6 +4651,8 @@ namespace ts {
     export interface UnionType extends UnionOrIntersectionType {
         /* @internal */
         resolvedReducedType: Type;
+        /* @internal */
+        regularType: UnionType;
     }
 
     export interface IntersectionType extends UnionOrIntersectionType {
Original file line number	Diff line number	Diff line change
`@@ -13457,9 +13457,13 @@ namespace ts {`
`13457`	`13457`	`return type;`
`13458`	`13458`	`}`
`13459`	`13459`
	`13460`	`+ function getRegularTypeOfUnion(type: UnionType) {`
	`13461`	`+ return type.regularType \|\| (type.regularType = getUnionType(sameMap((<UnionType>type).types, getRegularTypeOfLiteralType)) as UnionType);`
	`13462`	`+ }`
	`13463`	`+`
`13460`	`13464`	`function getRegularTypeOfLiteralType(type: Type): Type {`
`13461`	`13465`	`return type.flags & TypeFlags.Literal ? (<LiteralType>type).regularType :`
`13462`		`- type.flags & TypeFlags.Union ? getUnionType(sameMap((<UnionType>type).types, getRegularTypeOfLiteralType)) :`
	`13466`	`+ type.flags & TypeFlags.Union ? getRegularTypeOfUnion(<UnionType>type) :`
`13463`	`13467`	`type;`
`13464`	`13468`	`}`
`13465`	`13469`
Original file line number	Diff line number	Diff line change
`@@ -4651,6 +4651,8 @@ namespace ts {`
`4651`	`4651`	`export interface UnionType extends UnionOrIntersectionType {`
`4652`	`4652`	`/* @internal */`
`4653`	`4653`	`resolvedReducedType: Type;`
	`4654`	`+ /* @internal */`
	`4655`	`+ regularType: UnionType;`
`4654`	`4656`	`}`
`4655`	`4657`
`4656`	`4658`	`export interface IntersectionType extends UnionOrIntersectionType {`