CR

simulator/src/jack/compiler.ts

@@ -30,7 +30,11 @@ import {
   isPrimitive,
 } from "../languages/jack.js";
 import { Segment } from "../languages/vm.js";
-import { VM_BUILTINS } from "../vm/builtins.js";
+import {
+  VM_BUILTINS,
+  makeInterface,
+  overridesOsCorrectly,
+} from "../vm/builtins.js";
 import { validateSubroutine } from "./controlFlow.js";
 
 const osClasses = new Set([
@@ -299,16 +303,10 @@ export class Compiler {
 
     if (isOsClass(this.className)) {
       const builtin = VM_BUILTINS[`${this.className}.${subroutine.name.value}`];
-      const argTypes = subroutine.parameters.map((arg) => arg.type.value);
-
-      if (
-        builtin &&
-        (builtin.args.length != argTypes.length ||
-          builtin.args.some((arg, index) => arg != argTypes[index]) ||
-          builtin.returnType != subroutine.returnType.value)
-      ) {
+
+      if (builtin && !overridesOsCorrectly(this.className, subroutine)) {
         throw createError(
-          `OS subroutine ${this.className}.${subroutine.name.value} must follow the interface ${builtin.returnType} ${subroutine.name.value}(${builtin.args.join(",")})`,
+          `OS subroutine ${this.className}.${subroutine.name.value} must follow the interface ${makeInterface(subroutine.name.value, builtin)})`,
         );
       }
     }

simulator/src/vm/builtins.ts

@@ -1,4 +1,9 @@
-import { ReturnType, SubroutineType, Type } from "../languages/jack.js";
+import {
+  ReturnType,
+  Subroutine,
+  SubroutineType,
+  Type,
+} from "../languages/jack.js";
 import { VmMemory } from "./memory.js";
 import { ERRNO } from "./os/errors.js";
 import { OS } from "./os/os.js";
@@ -21,6 +26,23 @@ function getArgs(memory: VmMemory, n: number) {
   return args;
 }
 
+export function overridesOsCorrectly(cls: string, subroutine: Subroutine) {
+  const builtin = VM_BUILTINS[`${cls}.${subroutine.name.value}`];
+
+  return (
+    builtin &&
+    builtin.args.length == subroutine.parameters.length &&
+    builtin.args.every(
+      (arg, index) => arg == subroutine.parameters[index].type.value,
+    ) &&
+    builtin.returnType == subroutine.returnType.value
+  );
+}
+
+export function makeInterface(name: string, builtin: VmBuiltin) {
+  return `${builtin.returnType} ${name}(${builtin.args.join(",")}`;
+}
+
 export const VM_BUILTINS: Record<string, VmBuiltin> = {
   "Math.multiply": {
     func: (memory, _) => {