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 1/2] 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) {

From 33224747b33ddf6218bdf1e9006ff9bd87902cab Mon Sep 17 00:00:00 2001
From: Dick van den Brink <d_vandenbrink@outlook.com>
Date: Thu, 22 Jun 2017 16:45:09 +0200
Subject: [PATCH 2/2] Added test for unused typeparameters in a typealias
 declaration

---
 .../reference/unusedTypeParameters10.errors.txt          | 9 +++++++++
 tests/baselines/reference/unusedTypeParameters10.js      | 6 ++++++
 tests/cases/compiler/unusedTypeParameters10.ts           | 5 +++++
 3 files changed, 20 insertions(+)
 create mode 100644 tests/baselines/reference/unusedTypeParameters10.errors.txt
 create mode 100644 tests/baselines/reference/unusedTypeParameters10.js
 create mode 100644 tests/cases/compiler/unusedTypeParameters10.ts

diff --git a/tests/baselines/reference/unusedTypeParameters10.errors.txt b/tests/baselines/reference/unusedTypeParameters10.errors.txt
new file mode 100644
index 00000000000..7bfd5676df3
--- /dev/null
+++ b/tests/baselines/reference/unusedTypeParameters10.errors.txt
@@ -0,0 +1,9 @@
+tests/cases/compiler/unusedTypeParameters10.ts(1,12): error TS6133: 'T' is declared but never used.
+
+
+==== tests/cases/compiler/unusedTypeParameters10.ts (1 errors) ====
+    type Alias<T> = { };
+               ~
+!!! error TS6133: 'T' is declared but never used.
+    type Alias2<T> = { x: T };
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/unusedTypeParameters10.js b/tests/baselines/reference/unusedTypeParameters10.js
new file mode 100644
index 00000000000..5738e6f48e8
--- /dev/null
+++ b/tests/baselines/reference/unusedTypeParameters10.js
@@ -0,0 +1,6 @@
+//// [unusedTypeParameters10.ts]
+type Alias<T> = { };
+type Alias2<T> = { x: T };
+
+
+//// [unusedTypeParameters10.js]
diff --git a/tests/cases/compiler/unusedTypeParameters10.ts b/tests/cases/compiler/unusedTypeParameters10.ts
new file mode 100644
index 00000000000..cda482e5bdc
--- /dev/null
+++ b/tests/cases/compiler/unusedTypeParameters10.ts
@@ -0,0 +1,5 @@
+//@noUnusedLocals:true
+//@noUnusedParameters:true
+
+type Alias<T> = { };
+type Alias2<T> = { x: T };