From 4c82a2849f0dba8f6c51c7facbd95e68c388d324 Mon Sep 17 00:00:00 2001
From: ark120202 <ark120202@gmail.com>
Date: Fri, 19 Jul 2019 19:17:36 +0500
Subject: [PATCH] Fix readonly tuple detection

---
 src/TSHelper.ts          | 8 ++++----
 test/unit/tuples.spec.ts | 9 +++++++++
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/src/TSHelper.ts b/src/TSHelper.ts
index 6a9dc5a32..0d8276aa9 100644
--- a/src/TSHelper.ts
+++ b/src/TSHelper.ts
@@ -167,12 +167,12 @@ export function isExplicitArrayType(type: ts.Type, checker: ts.TypeChecker, prog
         return type.types.some(t => isExplicitArrayType(t, checker, program));
     }
 
-    if (isStandardLibraryType(type, "ReadonlyArray", program)) {
-        return true;
+    const flags = ts.NodeBuilderFlags.InTypeAlias | ts.NodeBuilderFlags.AllowEmptyTuple;
+    let typeNode = checker.typeToTypeNode(type, undefined, flags);
+    if (typeNode && ts.isTypeOperatorNode(typeNode) && typeNode.operator === ts.SyntaxKind.ReadonlyKeyword) {
+        typeNode = typeNode.type;
     }
 
-    const flags = ts.NodeBuilderFlags.InTypeAlias | ts.NodeBuilderFlags.AllowEmptyTuple;
-    const typeNode = checker.typeToTypeNode(type, undefined, flags);
     return typeNode !== undefined && (ts.isArrayTypeNode(typeNode) || ts.isTupleTypeNode(typeNode));
 }
 
diff --git a/test/unit/tuples.spec.ts b/test/unit/tuples.spec.ts
index 0f6aa6a39..4f527f29f 100644
--- a/test/unit/tuples.spec.ts
+++ b/test/unit/tuples.spec.ts
@@ -31,6 +31,15 @@ test("Tuple access", () => {
     expect(result).toBe(5);
 });
 
+test("Readonly Tuple access", () => {
+    const result = util.transpileAndExecute(
+        `const tuple: readonly [number, number, number] = [3,5,1];
+        return tuple[1];`
+    );
+
+    expect(result).toBe(5);
+});
+
 test("Tuple union access", () => {
     const result = util.transpileAndExecute(
         `function makeTuple(): [number, number, number] | [string, string, string] { return [3,5,1]; }