From e1d38c4f361441007430a621d6df5a4c1896bf96 Mon Sep 17 00:00:00 2001
From: JothamWong <45916998+JothamWong@users.noreply.github.com>
Date: Tue, 9 Apr 2024 15:54:18 +0800
Subject: [PATCH] Make runThread throw an error

---
 src/vm/oogavm-errors.ts    | 6 ++++++
 src/vm/oogavm-scheduler.ts | 5 +++--
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/src/vm/oogavm-errors.ts b/src/vm/oogavm-errors.ts
index 059d7aa..778f1af 100644
--- a/src/vm/oogavm-errors.ts
+++ b/src/vm/oogavm-errors.ts
@@ -31,6 +31,12 @@ export class HeapDeadError extends OogaError {
     }
 }
 
+export class RuntimeError extends OogaError {
+    constructor(msg: string) {
+        super(msg);
+    }
+}
+
 export class CompilerError extends OogaError {
     constructor(msg: string) {
         super(msg);
diff --git a/src/vm/oogavm-scheduler.ts b/src/vm/oogavm-scheduler.ts
index dd26491..87740e7 100644
--- a/src/vm/oogavm-scheduler.ts
+++ b/src/vm/oogavm-scheduler.ts
@@ -1,3 +1,5 @@
+import { RuntimeError } from './oogavm-errors.js';
+
 export type ThreadId = number;
 
 export interface Scheduler {
@@ -65,9 +67,8 @@ export class RoundRobinScheduler implements Scheduler {
     }
 
     runThread(): [ThreadId, number] | null {
-        // Arnav: When will this be 0? This will cause a crash because the callee assumes the tuple result
         if (this._idleThreads.length === 0) {
-            return null;
+            throw new RuntimeError("Expected a thread but nothing.");
         } else {
             // The ! is a non-null assertion operator
             const nextThread = this._idleThreads.shift()!;