From 871d6095efaf1d90e98a14f6cb1fc4223ad16911 Mon Sep 17 00:00:00 2001
From: Kanchalai Tanglertsampan <yuisu@microsoft.com>
Date: Tue, 21 Mar 2017 15:08:00 -0700
Subject: [PATCH] Report an error if dynamic import specifier is not assigable
 to type string

---
 src/compiler/checker.ts              | 4 ++++
 src/compiler/diagnosticMessages.json | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 51593839104..3b9b9166589 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -14873,6 +14873,10 @@ namespace ts {
                 grammarErrorOnNode(node, Diagnostics.Dynamic_import_cannot_be_used_when_targeting_ECMAScript_2015_modules);
             }
 
+            const specifierType = checkExpression(node.specifier);
+            if (!isTypeAssignableTo(specifierType, stringType)) {
+                error(node.specifier, Diagnostics.Dynamic_import_s_specifier_must_be_of_type_string_but_here_has_type_0, typeToString(specifierType));
+           }
             // resolveExternalModuleName will return undefined if the moduleReferenceExpression is not a string literal
             const moduleSymbol = resolveExternalModuleName(node, node.specifier);
             if (moduleSymbol) {
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index 8e1ee767c55..5e200cf4a93 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -3165,6 +3165,10 @@
       "category": "Error",
       "code": 7035
     },
+    "Dynamic import's specifier must be of type 'string', but here has type '{0}'.": {
+      "category": "Error",
+      "code": 7036
+    },
     "You cannot rename this element.": {
         "category": "Error",
         "code": 8000