Fix invalid cast (microsoft#26462)

Andy · web-flow · commit fd948ac6d2a0 · 2018-08-15T10:17:18.000-07:00
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
@@ -26696,7 +26696,7 @@ namespace ts {
                 case SyntaxKind.ParenthesizedType:
                 case SyntaxKind.OptionalType:
                 case SyntaxKind.RestType:
-                    return checkSourceElement((<ParenthesizedTypeNode | OptionalTypeNode>node).type);
+                    return checkSourceElement((<ParenthesizedTypeNode | OptionalTypeNode | RestTypeNode>node).type);
                 case SyntaxKind.ThisType:
                     return checkThisType(<ThisTypeNode>node);
                 case SyntaxKind.TypeOperator:
