Cherry-pick PR #50797 into release-4.8 (#50798)

Component commits:
23a1dd4 Fix bounds check

23784d7 Add regression test

Co-authored-by: Anders Hejlsberg <[email protected]>

Author: TypeScript Bot

src/compiler/checker.ts

@@ -35931,8 +35931,8 @@ 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];
         }

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";

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
+

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
+

tests/cases/compiler/inferTypeConstraintInstantiationCircularity.ts

@@ -70,4 +70,22 @@ 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