From 01c96868697163cbb4f6f7135a882d14eeaa31e8 Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Mon, 18 Jan 2016 17:35:10 -0800
Subject: [PATCH] Allow 'readonly' only on property and index signature
 declarations

---
 src/compiler/checker.ts              | 9 +++------
 src/compiler/diagnosticMessages.json | 4 ++++
 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 9fcf951ce83..937065cd559 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -10378,7 +10378,7 @@ namespace ts {
         }
 
         function isReadonlySymbol(symbol: Symbol): boolean {
-            if (symbol.flags & (SymbolFlags.Property | SymbolFlags.Method)) {
+            if (symbol.flags & SymbolFlags.Property) {
                 return symbol === undefinedSymbol || (getDeclarationFlagsFromSymbol(symbol) & NodeFlags.Readonly) !== 0;
             }
             if (symbol.flags & SymbolFlags.Accessor) {
@@ -15786,11 +15786,8 @@ namespace ts {
                         if (flags & NodeFlags.Readonly) {
                             return grammarErrorOnNode(modifier, Diagnostics._0_modifier_already_seen, "readonly");
                         }
-                        else if (flags & NodeFlags.Async) {
-                            return grammarErrorOnNode(modifier, Diagnostics._0_modifier_must_precede_1_modifier, "readonly", "async");
-                        }
-                        else if (node.parent.kind === SyntaxKind.ModuleBlock || node.parent.kind === SyntaxKind.SourceFile) {
-                            return grammarErrorOnNode(modifier, Diagnostics._0_modifier_cannot_appear_on_a_module_element, "readonly");
+                        else if (node.kind !== SyntaxKind.PropertyDeclaration && node.kind !== SyntaxKind.PropertySignature && node.kind !== SyntaxKind.IndexSignature) {
+                            return grammarErrorOnNode(modifier, Diagnostics.readonly_modifier_can_only_appear_on_a_property_declaration_or_index_signature);
                         }
                         flags |= NodeFlags.Readonly;
                         lastReadonly = modifier;
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index 6599a35f494..fc4aae4ed30 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -67,6 +67,10 @@
         "category": "Error",
         "code": 1023
     },
+    "'readonly' modifier can only appear on a property declaration or index signature.": {
+        "category": "Error",
+        "code": 1024
+    },
     "Accessibility modifier already seen.": {
         "category": "Error",
         "code": 1028