Throw for DataView targets of borrowed typed array set calls

packages/compiler/src/frontend/lowering/containers/bytes.ts

@@ -927,8 +927,9 @@ function bytesSetIntrinsic(
 
 /** `Uint8Array.prototype.set.call(target, src, offset?)`, through any typed
  * array constructor's prototype (they share %TypedArray%.prototype.set). A
- * typed-array target lowers like `target.set(src, offset)`. Any other
- * target is checked at run time: a typed array calls its `set`, and
+ * target the checker types as a typed array or Buffer lowers like
+ * `target.set(src, offset)`. Any other target, a DataView included, is
+ * checked at run time: a typed array calls its `set`, and
  * anything else throws Node's TypeError "this is not a typed array.",
  * after every argument is evaluated. */
 export function lowerBytesPrototypeSetCall(
@@ -961,7 +962,16 @@ export function lowerBytesPrototypeSetCall(
   if (argNodes.length < 2 || argNodes.length > 3 || argNodes.some(ts.isSpreadElement)) return null;
   const loc = locOf(call);
   const target = lowerer.lowerExpr(argNodes[0]!);
-  if (target.type.kind === "bytes")
+  // A DataView lowers to the same bytes type, so the checker type decides:
+  // only a typed array (or a Buffer) takes the method's path.
+  const targetSymbol = lowerer.typeOf(argNodes[0]!).getSymbol();
+  if (
+    target.type.kind === "bytes" &&
+    targetSymbol !== undefined &&
+    lowerer.isStdlibSymbol(targetSymbol) &&
+    (own(BYTES_CTORS, ts.symbolName(targetSymbol)) !== undefined ||
+      ts.symbolName(targetSymbol) === "Buffer")
+  )
     return bytesSetIntrinsic(lowerer, target, argNodes.slice(1), loc);
   const slot = (value: IrExpr): { decl: IrStmt; read: IrExpr } => {
     const local = lowerer.declareHiddenLocal("%setArg", DYN);

packages/compiler/test/ts7/baselines/order-parity/tests/corpus/8100-typed-array-prototype-set-data-view.ts.json

@@ -0,0 +1,6 @@
+{
+ "order": [
+  "<repo>/tests/corpus/8100-typed-array-prototype-set-data-view.ts"
+ ],
+ "diags": []
+}

tests/corpus/8100-typed-array-prototype-set-data-view.ts

@@ -0,0 +1,30 @@
+// A borrowed TypedArray.prototype.set over a DataView target throws Node's
+// TypeError after evaluating its arguments, and leaves the view unchanged.
+const view = new DataView(new ArrayBuffer(4));
+const order: string[] = [];
+function arg<T>(label: string, value: T): T {
+  order.push(label);
+  return value;
+}
+try {
+  Uint8Array.prototype.set.call(arg("target", view), arg("source", [1, 2]), arg("offset", 1));
+  console.log("set");
+} catch (e) {
+  console.log(e instanceof TypeError, (e as Error).message, order.join(","));
+}
+console.log(view.getUint8(1), view.getUint8(2));
+
+function fill(target: DataView | Uint8Array, bytes: number[]): string {
+  try {
+    Uint8Array.prototype.set.call(target, bytes);
+    return "set";
+  } catch (e) {
+    return (e as Error).message;
+  }
+}
+console.log(fill(view, [7]), view.getUint8(0));
+const bytes = new Uint8Array(2);
+console.log(fill(bytes, [7]), bytes[0]);
+const buffer = Buffer.alloc(3);
+Uint8Array.prototype.set.call(buffer, [4, 5], 1);
+console.log(buffer.toString("hex"));