From 97ef839a03fc16ea1aa5a7242ed68ad26814443f Mon Sep 17 00:00:00 2001
From: Nathan Shively-Sanders <nathansa@microsoft.com>
Date: Fri, 22 Jul 2016 13:48:43 -0700
Subject: [PATCH] Protected ctors are accessible in subclass static methods

Previously, it was an error to refer to a protected constructor from a
base class, even in a static method where the semantics work. Now it is
not an error in static methods.
---
 src/compiler/checker.ts | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 1cebd469388..ff248d75941 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -11544,8 +11544,23 @@ namespace ts {
             const declaringClassDeclaration = <ClassLikeDeclaration>getClassLikeDeclarationOfSymbol(declaration.parent.symbol);
             const declaringClass = <InterfaceType>getDeclaredTypeOfSymbol(declaration.parent.symbol);
 
-            // A private or protected constructor can only be instantiated within it's own class
+            // A private or protected constructor can only be instantiated within its own class or a static method of a subclass
             if (!isNodeWithinClass(node, declaringClassDeclaration)) {
+                const containingFunction = getContainingFunction(node);
+                const containingClass = getContainingClass(node);
+                if (containingClass) {
+                    const containingType = getTypeOfNode(containingClass);
+                    const baseTypes = getBaseTypes(<InterfaceType>containingType);
+                    if (baseTypes.length) {
+                        const baseType = baseTypes[0];
+                        if (containingFunction &&
+                            containingFunction.flags & NodeFlags.Static &&
+                            flags & NodeFlags.Protected &&
+                            baseType.symbol === declaration.parent.symbol) {
+                            return true;
+                        }
+                    }
+                }
                 if (flags & NodeFlags.Private) {
                     error(node, Diagnostics.Constructor_of_class_0_is_private_and_only_accessible_within_the_class_declaration, typeToString(declaringClass));
                 }