runtime: honor fromIndex for Array and TypedArray indexOf/includes

[andrewtdiz]

Summary

Array.prototype.indexOf, Array.prototype.includes, and the matching %TypedArray% methods should honor the optional fromIndex argument. Perry's static indexOf / includes codegen currently accepts exactly one argument, and the runtime helpers / dynamic dispatch paths only search from index 0.

Node parity probe

Run with Node v25.9.0:

const arr = [1, 2, 1, NaN];
const ta = new Float64Array([1, 2, 1, NaN]);
for (const [label, recv] of [["Array", arr], ["TypedArray", ta]]) {
  for (const [caseLabel, fn] of [
    ["indexOf from 1", () => recv.indexOf(1, 1)],
    ["indexOf from -2", () => recv.indexOf(1, -2)],
    ["indexOf from Infinity", () => recv.indexOf(1, Infinity)],
    ["includes NaN", () => recv.includes(NaN)],
    ["includes from 4", () => recv.includes(1, 4)],
    ["includes from -2", () => recv.includes(1, -2)],
    ["includes from Infinity", () => recv.includes(1, Infinity)],
  ]) {
    try {
      console.log(`${label}.${caseLabel}: ${JSON.stringify(fn())}`);
    } catch (e) {
      console.log(`${label}.${caseLabel}: throws ${e.name}: ${e.message}`);
    }
  }
}

Output:

Array.indexOf from 1: 2
Array.indexOf from -2: 2
Array.indexOf from Infinity: -1
Array.includes NaN: true
Array.includes from 4: false
Array.includes from -2: true
Array.includes from Infinity: false
TypedArray.indexOf from 1: 2
TypedArray.indexOf from -2: 2
TypedArray.indexOf from Infinity: -1
TypedArray.includes NaN: true
TypedArray.includes from 4: false
TypedArray.includes from -2: true
TypedArray.includes from Infinity: false

Current Perry behavior in source

lastIndexOf already has an optional-from path, but forward search does not:

• crates/perry-codegen/src/lower_array_method.rs:420-450 requires Array.includes to have exactly one argument and calls js_array_includes_jsvalue(arr, value).
• crates/perry-codegen/src/lower_array_method.rs:451-472 requires Array.indexOf to have exactly one argument and calls js_array_indexOf_jsvalue(arr, value).
• By contrast, crates/perry-codegen/src/lower_array_method.rs:474-492 accepts one or two args for lastIndexOf and passes fromIndex plus a has_from flag.

The runtime helpers also search from the beginning only:

• crates/perry-runtime/src/array/search.rs:41-65 implements js_array_indexOf_jsvalue(arr, value) and loops from 0 for Arrays and TypedArrays.
• crates/perry-runtime/src/array/search.rs:175-206 implements js_array_includes_jsvalue(arr, value) and loops from 0 for Arrays and TypedArrays while using SameValueZero.
• crates/perry-runtime/src/object/native_call_method.rs:1262-1271 dynamic dispatch for indexOf / includes reads only the first argument and calls those two-argument helpers.

So indexOf(value, fromIndex) and includes(value, fromIndex) either fail the static codegen arity check or silently ignore fromIndex in dynamic dispatch.

Expected fix shape

Add from-index-aware helpers or extend the existing helpers so both static and dynamic paths can pass the optional second argument:

• Omitted fromIndex: start at 0.
• Positive finite fromIndex: start at that index, returning not-found when it is >= length.
• Negative fromIndex: start at max(length + fromIndex, 0).
• NaN: treat as 0.
• Infinity: return not-found for forward search.
• Preserve indexOf strict-equality behavior and includes SameValueZero behavior, including includes(NaN) === true.

Please cover Array and TypedArray receivers, static and dynamic dispatch, and fromIndex values undefined, positive, negative, NaN, and Infinity.

Related but separate: #2457 / PR #2501 covered TypedArray lastIndexOf; this issue is for forward indexOf / includes optional fromIndex handling.