From a5cda4633bab250114fa24a87d02d495c01e6ef7 Mon Sep 17 00:00:00 2001
From: Troy Tae <tjy970721@gmail.com>
Date: Wed, 18 Sep 2019 16:19:18 +0900
Subject: [PATCH] fix: permit string/number literal in union type

---
 src/compiler/checker.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index f8c88178885..5f88cd7bebc 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -32797,7 +32797,7 @@ namespace ts {
                         typeToString(node.type ? getTypeFromTypeNode(node.type) : anyType));
                 }
 
-                if (type.flags & TypeFlags.Union && allTypesAssignableToKind(type, TypeFlags.StringLiteral, /*strict*/ true)) {
+                if (type.flags & TypeFlags.Union && allTypesAssignableToKind(type, TypeFlags.StringOrNumberLiteral, /*strict*/ true)) {
                     return grammarErrorOnNode(parameter.name,
                         Diagnostics.An_index_signature_parameter_type_cannot_be_a_union_type_Consider_using_a_mapped_object_type_instead);
                 }