From 3b84f76fb23bd39d14c7243e5cd495fd207916c0 Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Fri, 16 Sep 2022 07:14:14 -0700
Subject: [PATCH] Fix crash caused by incorrect bounds check (regression in
 4.8) (#50797)

* Fix bounds check

* Add regression test
---
 src/compiler/checker.ts                       |  4 +-
 ...rTypeConstraintInstantiationCircularity.js | 21 +++++++-
 ...ConstraintInstantiationCircularity.symbols | 48 +++++++++++++++++++
 ...peConstraintInstantiationCircularity.types | 31 ++++++++++++
 ...rTypeConstraintInstantiationCircularity.ts | 20 +++++++-
 5 files changed, 120 insertions(+), 4 deletions(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 9f38c49c50a31..32cee9afa06da 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -36070,8 +36070,8 @@ namespace ts {
         }
 
         function getEffectiveTypeArgumentAtIndex(node: TypeReferenceNode | ExpressionWithTypeArguments, typeParameters: readonly TypeParameter[], index: number): Type {
-            if (index < typeParameters.length) {
-                return getTypeFromTypeNode(node.typeArguments![index]);
+            if (node.typeArguments && index < node.typeArguments.length) {
+                return getTypeFromTypeNode(node.typeArguments[index]);
             }
             return getEffectiveTypeArguments(node, typeParameters)[index];
         }
diff --git a/tests/baselines/reference/inferTypeConstraintInstantiationCircularity.js b/tests/baselines/reference/inferTypeConstraintInstantiationCircularity.js
index ca1488ed98615..e47b01ff47753 100644
--- a/tests/baselines/reference/inferTypeConstraintInstantiationCircularity.js
+++ b/tests/baselines/reference/inferTypeConstraintInstantiationCircularity.js
@@ -70,7 +70,26 @@ type MyObject<T> = T extends ZodObject<infer U>
   ? U extends ZodRawShape
     ? U
     : never
-  : never;
+  : never;
+
+// Repro from #50479
+
+type Cell<Value extends BaseValue = any, BaseValue = unknown> = {
+  id: string
+}
+
+type Items<Type extends Cell = Cell> = {
+  type: Type
+  name: string
+}
+
+type InferIOItemToJSType<T extends Items> =
+  T extends { type: infer U }
+    ? U extends Cell<infer V/**, infer _ or unknown, or any valid type **/>
+      ? V
+      : never
+    : never
+
 
 //// [inferTypeConstraintInstantiationCircularity.js]
 "use strict";
diff --git a/tests/baselines/reference/inferTypeConstraintInstantiationCircularity.symbols b/tests/baselines/reference/inferTypeConstraintInstantiationCircularity.symbols
index 4feca7bdc5e0f..10837383c8843 100644
--- a/tests/baselines/reference/inferTypeConstraintInstantiationCircularity.symbols
+++ b/tests/baselines/reference/inferTypeConstraintInstantiationCircularity.symbols
@@ -204,3 +204,51 @@ type MyObject<T> = T extends ZodObject<infer U>
 
     : never
   : never;
+
+// Repro from #50479
+
+type Cell<Value extends BaseValue = any, BaseValue = unknown> = {
+>Cell : Symbol(Cell, Decl(inferTypeConstraintInstantiationCircularity.ts, 71, 10))
+>Value : Symbol(Value, Decl(inferTypeConstraintInstantiationCircularity.ts, 75, 10))
+>BaseValue : Symbol(BaseValue, Decl(inferTypeConstraintInstantiationCircularity.ts, 75, 40))
+>BaseValue : Symbol(BaseValue, Decl(inferTypeConstraintInstantiationCircularity.ts, 75, 40))
+
+  id: string
+>id : Symbol(id, Decl(inferTypeConstraintInstantiationCircularity.ts, 75, 65))
+}
+
+type Items<Type extends Cell = Cell> = {
+>Items : Symbol(Items, Decl(inferTypeConstraintInstantiationCircularity.ts, 77, 1))
+>Type : Symbol(Type, Decl(inferTypeConstraintInstantiationCircularity.ts, 79, 11))
+>Cell : Symbol(Cell, Decl(inferTypeConstraintInstantiationCircularity.ts, 71, 10))
+>Cell : Symbol(Cell, Decl(inferTypeConstraintInstantiationCircularity.ts, 71, 10))
+
+  type: Type
+>type : Symbol(type, Decl(inferTypeConstraintInstantiationCircularity.ts, 79, 40))
+>Type : Symbol(Type, Decl(inferTypeConstraintInstantiationCircularity.ts, 79, 11))
+
+  name: string
+>name : Symbol(name, Decl(inferTypeConstraintInstantiationCircularity.ts, 80, 12))
+}
+
+type InferIOItemToJSType<T extends Items> =
+>InferIOItemToJSType : Symbol(InferIOItemToJSType, Decl(inferTypeConstraintInstantiationCircularity.ts, 82, 1))
+>T : Symbol(T, Decl(inferTypeConstraintInstantiationCircularity.ts, 84, 25))
+>Items : Symbol(Items, Decl(inferTypeConstraintInstantiationCircularity.ts, 77, 1))
+
+  T extends { type: infer U }
+>T : Symbol(T, Decl(inferTypeConstraintInstantiationCircularity.ts, 84, 25))
+>type : Symbol(type, Decl(inferTypeConstraintInstantiationCircularity.ts, 85, 13))
+>U : Symbol(U, Decl(inferTypeConstraintInstantiationCircularity.ts, 85, 25))
+
+    ? U extends Cell<infer V/**, infer _ or unknown, or any valid type **/>
+>U : Symbol(U, Decl(inferTypeConstraintInstantiationCircularity.ts, 85, 25))
+>Cell : Symbol(Cell, Decl(inferTypeConstraintInstantiationCircularity.ts, 71, 10))
+>V : Symbol(V, Decl(inferTypeConstraintInstantiationCircularity.ts, 86, 26))
+
+      ? V
+>V : Symbol(V, Decl(inferTypeConstraintInstantiationCircularity.ts, 86, 26))
+
+      : never
+    : never
+
diff --git a/tests/baselines/reference/inferTypeConstraintInstantiationCircularity.types b/tests/baselines/reference/inferTypeConstraintInstantiationCircularity.types
index 4571ec23357eb..ffdc2752dca62 100644
--- a/tests/baselines/reference/inferTypeConstraintInstantiationCircularity.types
+++ b/tests/baselines/reference/inferTypeConstraintInstantiationCircularity.types
@@ -101,3 +101,34 @@ type MyObject<T> = T extends ZodObject<infer U>
     ? U
     : never
   : never;
+
+// Repro from #50479
+
+type Cell<Value extends BaseValue = any, BaseValue = unknown> = {
+>Cell : Cell<Value, BaseValue>
+
+  id: string
+>id : string
+}
+
+type Items<Type extends Cell = Cell> = {
+>Items : Items<Type>
+
+  type: Type
+>type : Type
+
+  name: string
+>name : string
+}
+
+type InferIOItemToJSType<T extends Items> =
+>InferIOItemToJSType : InferIOItemToJSType<T>
+
+  T extends { type: infer U }
+>type : U
+
+    ? U extends Cell<infer V/**, infer _ or unknown, or any valid type **/>
+      ? V
+      : never
+    : never
+
diff --git a/tests/cases/compiler/inferTypeConstraintInstantiationCircularity.ts b/tests/cases/compiler/inferTypeConstraintInstantiationCircularity.ts
index ad489da708312..6adf71624e28c 100644
--- a/tests/cases/compiler/inferTypeConstraintInstantiationCircularity.ts
+++ b/tests/cases/compiler/inferTypeConstraintInstantiationCircularity.ts
@@ -70,4 +70,22 @@ type MyObject<T> = T extends ZodObject<infer U>
   ? U extends ZodRawShape
     ? U
     : never
-  : never;
\ No newline at end of file
+  : never;
+
+// Repro from #50479
+
+type Cell<Value extends BaseValue = any, BaseValue = unknown> = {
+  id: string
+}
+
+type Items<Type extends Cell = Cell> = {
+  type: Type
+  name: string
+}
+
+type InferIOItemToJSType<T extends Items> =
+  T extends { type: infer U }
+    ? U extends Cell<infer V/**, infer _ or unknown, or any valid type **/>
+      ? V
+      : never
+    : never