From 385debec5f50ff96d561b9a3a52b041e586924c3 Mon Sep 17 00:00:00 2001
From: Blaine Bublitz <blaine.bublitz@gmail.com>
Date: Thu, 18 May 2017 14:19:30 -0700
Subject: [PATCH 1/2] Make {create/update}TypeAliasDeclaration API consistent
 (closes #15918)

---
 src/compiler/factory.ts | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/src/compiler/factory.ts b/src/compiler/factory.ts
index 63c2028c424..80e3e995e38 100644
--- a/src/compiler/factory.ts
+++ b/src/compiler/factory.ts
@@ -1502,19 +1502,23 @@ namespace ts {
             : node;
     }
 
-    export function createTypeAliasDeclaration(name: string | Identifier, typeParameters: TypeParameterDeclaration[] | undefined, type: TypeNode) {
+    export function createTypeAliasDeclaration(decorators: Decorator[] | undefined, modifiers: Modifier[] | undefined, name: string | Identifier, typeParameters: TypeParameterDeclaration[] | undefined, type: TypeNode) {
         const node = <TypeAliasDeclaration>createSynthesizedNode(SyntaxKind.TypeAliasDeclaration);
+        node.decorators = asNodeArray(decorators);
+        node.modifiers = asNodeArray(modifiers);
         node.name = asName(name);
         node.typeParameters = asNodeArray(typeParameters);
         node.type = type;
         return node;
     }
 
-    export function updateTypeAliasDeclaration(node: TypeAliasDeclaration, name: Identifier, typeParameters: TypeParameterDeclaration[] | undefined, type: TypeNode) {
-        return node.name !== name
+    export function updateTypeAliasDeclaration(node: TypeAliasDeclaration, decorators: Decorator[] | undefined, modifiers: Modifier[] | undefined, name: Identifier, typeParameters: TypeParameterDeclaration[] | undefined, type: TypeNode) {
+        return node.decorators !== decorators
+            || node.modifiers !== modifiers
+            || node.name !== name
             || node.typeParameters !== typeParameters
             || node.type !== type
-            ? updateNode(createTypeAliasDeclaration(name, typeParameters, type), node)
+            ? updateNode(createTypeAliasDeclaration(decorators, modifiers, name, typeParameters, type), node)
             : node;
     }
 

From 226b2ef08742ac3500a744b5c65563c2eca10afe Mon Sep 17 00:00:00 2001
From: Blaine Bublitz <blaine.bublitz@gmail.com>
Date: Fri, 19 May 2017 15:20:31 -0700
Subject: [PATCH 2/2] Fix updateTypeAliasDeclaration call

---
 src/compiler/visitor.ts | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/compiler/visitor.ts b/src/compiler/visitor.ts
index eb28721a142..af18a5620c6 100644
--- a/src/compiler/visitor.ts
+++ b/src/compiler/visitor.ts
@@ -700,6 +700,8 @@ namespace ts {
 
             case SyntaxKind.TypeAliasDeclaration:
                 return updateTypeAliasDeclaration(<TypeAliasDeclaration>node,
+                    nodesVisitor((<TypeAliasDeclaration>node).decorators, visitor, isDecorator),
+                    nodesVisitor((<TypeAliasDeclaration>node).modifiers, visitor, isModifier),
                     visitNode((<TypeAliasDeclaration>node).name, visitor, isIdentifier),
                     nodesVisitor((<TypeAliasDeclaration>node).typeParameters, visitor, isTypeParameter),
                     visitNode((<TypeAliasDeclaration>node).type, visitor, isTypeNode));