Out of bounds tuple elements have type 'undefined'

ahejlsberg · ahejlsberg · commit 7cdc65b2a5ec · 2019-06-21T18:00:26.000-10:00
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
@@ -14440,7 +14440,7 @@ namespace ts {
             if (propType) {
                 return propType;
             }
-            if (everyType(type, isTupleType) && !everyType(type, t => !(<TupleTypeReference>t).target.hasRestElement)) {
+            if (everyType(type, isTupleType)) {
                 return mapType(type, t => getRestTypeOfTupleType(<TupleTypeReference>t) || undefinedType);
             }
             return undefined;

Original file line number	Diff line number	Diff line change
`@@ -14440,7 +14440,7 @@ namespace ts {`
`14440`	`14440`	`if (propType) {`
`14441`	`14441`	`return propType;`
`14442`	`14442`	`}`
`14443`		`- if (everyType(type, isTupleType) && !everyType(type, t => !(<TupleTypeReference>t).target.hasRestElement)) {`
	`14443`	`+ if (everyType(type, isTupleType)) {`
`14444`	`14444`	`return mapType(type, t => getRestTypeOfTupleType(<TupleTypeReference>t) \|\| undefinedType);`
`14445`	`14445`	`}`
`14446`	`14446`	`return undefined;`