From a8bea77d1efe4984e573760770b78486a5488366 Mon Sep 17 00:00:00 2001
From: Wesley Wigham <wewigham@microsoft.com>
Date: Wed, 2 Oct 2019 14:50:12 -0700
Subject: [PATCH] Backfill TypeReference.typeArguments in the API (#33714)

---
 src/services/services.ts                           | 9 +++++++++
 src/services/types.ts                              | 4 ++++
 tests/baselines/reference/api/tsserverlibrary.d.ts | 3 +++
 tests/baselines/reference/api/typescript.d.ts      | 3 +++
 4 files changed, 19 insertions(+)

diff --git a/src/services/services.ts b/src/services/services.ts
index 6a1c721cbba..acd06a8ac6d 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -452,6 +452,15 @@ namespace ts {
         isClass(): this is InterfaceType {
             return !!(getObjectFlags(this) & ObjectFlags.Class);
         }
+        /**
+         * This polyfills `referenceType.typeArguments` for API consumers
+         */
+        get typeArguments() {
+            if (getObjectFlags(this) & ObjectFlags.Reference) {
+                return this.checker.getTypeArguments(this as Type as TypeReference);
+            }
+            return undefined;
+        }
     }
 
     class SignatureObject implements Signature {
diff --git a/src/services/types.ts b/src/services/types.ts
index 65544d5677d..80a4c4c0650 100644
--- a/src/services/types.ts
+++ b/src/services/types.ts
@@ -68,6 +68,10 @@ namespace ts {
         isClass(): this is InterfaceType;
     }
 
+    export interface TypeReference {
+        typeArguments?: readonly Type[];
+    }
+
     export interface Signature {
         getDeclaration(): SignatureDeclaration;
         getTypeParameters(): TypeParameter[] | undefined;
diff --git a/tests/baselines/reference/api/tsserverlibrary.d.ts b/tests/baselines/reference/api/tsserverlibrary.d.ts
index 5ad30ae8803..0a1c7230dc8 100644
--- a/tests/baselines/reference/api/tsserverlibrary.d.ts
+++ b/tests/baselines/reference/api/tsserverlibrary.d.ts
@@ -4902,6 +4902,9 @@ declare namespace ts {
         isClassOrInterface(): this is InterfaceType;
         isClass(): this is InterfaceType;
     }
+    interface TypeReference {
+        typeArguments?: readonly Type[];
+    }
     interface Signature {
         getDeclaration(): SignatureDeclaration;
         getTypeParameters(): TypeParameter[] | undefined;
diff --git a/tests/baselines/reference/api/typescript.d.ts b/tests/baselines/reference/api/typescript.d.ts
index 7bf245876e5..932199e6e36 100644
--- a/tests/baselines/reference/api/typescript.d.ts
+++ b/tests/baselines/reference/api/typescript.d.ts
@@ -4902,6 +4902,9 @@ declare namespace ts {
         isClassOrInterface(): this is InterfaceType;
         isClass(): this is InterfaceType;
     }
+    interface TypeReference {
+        typeArguments?: readonly Type[];
+    }
     interface Signature {
         getDeclaration(): SignatureDeclaration;
         getTypeParameters(): TypeParameter[] | undefined;