From 09be5377869041412a222d10be5ddb60ed7d4d29 Mon Sep 17 00:00:00 2001
From: Dick van den Brink <d_vandenbrink@outlook.com>
Date: Thu, 22 Jun 2017 16:41:40 +0200
Subject: [PATCH] Also check TypeAlias for unused type parameters Fixes #15208

---
 src/compiler/checker.ts | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 05c20ffb11a..e5c63cbd50c 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -19426,6 +19426,9 @@ namespace ts {
                         case SyntaxKind.ConstructorType:
                             checkUnusedTypeParameters(<FunctionLikeDeclaration>node);
                             break;
+                        case SyntaxKind.TypeAliasDeclaration:
+                            checkUnusedTypeParameters(<TypeAliasDeclaration>node);
+                            break;
                     }
                 }
             }
@@ -19503,7 +19506,7 @@ namespace ts {
             }
         }
 
-        function checkUnusedTypeParameters(node: ClassDeclaration | ClassExpression | FunctionDeclaration | MethodDeclaration | FunctionExpression | ArrowFunction | ConstructorDeclaration | SignatureDeclaration | InterfaceDeclaration) {
+        function checkUnusedTypeParameters(node: ClassDeclaration | ClassExpression | FunctionDeclaration | MethodDeclaration | FunctionExpression | ArrowFunction | ConstructorDeclaration | SignatureDeclaration | InterfaceDeclaration | TypeAliasDeclaration) {
             if (compilerOptions.noUnusedLocals && !isInAmbientContext(node)) {
                 if (node.typeParameters) {
                     // Only report errors on the last declaration for the type parameter container;
@@ -21208,6 +21211,7 @@ namespace ts {
             checkTypeNameIsReserved(node.name, Diagnostics.Type_alias_name_cannot_be_0);
             checkTypeParameters(node.typeParameters);
             checkSourceElement(node.type);
+            registerForUnusedIdentifiersCheck(node);
         }
 
         function computeEnumMemberValues(node: EnumDeclaration) {