scriptc/packages/compiler/test/inline-array-fields.test.ts

import { mkdtemp, readFile, rm, symlink, writeFile } from "node:fs/promises";
import { tmpdir } from "node:os";
import { join } from "node:path";
import { expect, test } from "vitest";
import { compile } from "../src/index.js";

// InlineArray fields (@scriptc/experimental, ir/inline-arrays.ts): the
// elements of a ProgramLifetime class's array field written once from a
// constructor parameter live in the instance, after its fixed fields.

const repoRoot = join(import.meta.dirname, "../../..");

const header = `
import type { ProgramLifetime } from "@scriptc/types";
import type { InlineArray } from "@scriptc/experimental";
`;

async function build(
  source: string,
): Promise<{ ok: boolean; codes: string[]; llvm: string; messages: string[] }> {
  const dir = await mkdtemp(join(tmpdir(), "scriptc-inline-array-"));
  try {
    // The workspace's packages, so that the program resolves both imports.
    await symlink(join(repoRoot, "node_modules"), join(dir, "node_modules"));
    const entry = join(dir, "main.ts");
    const outPath = join(dir, "main.ll");
    await writeFile(entry, header + source);
    const result = await compile(entry, { outDir: dir, outPath, outputKind: "llvm" });
    const llvm = result.ok ? await readFile(outPath, "utf8") : "";
    return {
      ok: result.ok,
      codes: (result.diagnostics ?? []).map((d) => d.code),
      messages: (result.diagnostics ?? []).map((d) => d.message),
      llvm,
    };
  } finally {
    await rm(dir, { recursive: true, force: true });
  }
}

const classes = `
class Item implements ProgramLifetime {
  readonly kind: number;
  constructor(kind: number) {
    this.kind = kind;
  }
}
class List implements ProgramLifetime {
  readonly pos: number;
  readonly items: InlineArray<Item>;
  constructor(pos: number, items: readonly Item[]) {
    this.pos = pos;
    this.items = items;
  }
}
class Flagged extends List {
  readonly flags: number;
  constructor(pos: number, items: readonly Item[], flags: number) {
    super(pos, items);
    this.flags = flags;
  }
}
`;

const body = (fn: string, llvm: string): string =>
  new RegExp(`^define internal [^@]+@sc_bf_${fn}\\([^]*?^}`, "m").exec(llvm)?.[0] ?? "";

// The inline layout applies to executables whose compact instances live in
// the low region: Linux, 64-bit.
const lowRegion =
  process.platform === "linux" && (process.arch === "x64" || process.arch === "arm64");

test.runIf(lowRegion)("the elements follow the fixed fields, which keep their count", async () => {
  const { ok, llvm } = await build(
    classes +
      `
const a = new List(1, [new Item(1), new Item(2)]);
const b = new Flagged(2, [new Item(3)], 7);
console.log(a.items.length, b.items.length, b.flags);
`,
  );
  expect(ok).toBe(true);
  // The field's slot is an i32: the header, pos and the count.
  expect(llvm).toMatch(/^%sc_o_List = type \{ i32, i32, i32 \}/m);
  expect(llvm).toMatch(/^%sc_o_Flagged = type \{ i32, i32, i32, i32 \}/m);
  // `new` takes the count and allocates room for the 32-bit references
  // after the largest fixed part in the subtree (Flagged's 16 bytes).
  expect(llvm).toContain("define internal ptr @sc_new_List(i32 %inl.len)");
  expect(llvm).toContain("%inl.size = add nuw nsw i64 %inl.bytes, 16");
  // The constructor copies the argument's elements into the instance.
  expect(llvm).toContain("call void @scr_arr_copy_cref_tail(");
});

test.runIf(lowRegion)("indexing, length and local aliases read the instance", async () => {
  const { ok, llvm } = await build(
    classes +
      `
function sum(list: List): number {
  let s = 0;
  const items = list.items;
  for (let i = 0; i < items.length; i++) s += items[i]!.kind;
  for (const item of list.items) s += item.kind;
  return s + list.items[0]!.kind;
}
const list = new List(0, [new Item(1), new Item(2)]);
console.log(sum(list));
`,
  );
  expect(ok).toBe(true);
  const sum = body("sum", llvm);
  expect(sum).not.toBe("");
  // Elements are 32-bit references loaded from the instance; only the
  // out-of-bounds path makes an array of them, for the runtime getter.
  expect(sum).toMatch(/getelementptr inbounds i32, ptr %\S+, i64 %\S+\n\s*%\S+ = load i32/);
  const hits = sum.split(/\n(?=\S)/).filter((block) => block.startsWith("inl.get.hit"));
  expect(hits.length).toBeGreaterThan(0);
  for (const block of hits) expect(block).not.toContain("scr_arr_view_cref");
  for (const line of sum.split("\n").filter((l) => l.includes("scr_arr_view_cref(")))
    expect(line).not.toContain("scr_arr_get_ref");
});

test.runIf(lowRegion)("for...of tests presence on the instance", async () => {
  const { ok, llvm } = await build(
    classes +
      `
// An array that may have holes: each loop over a list tests each index.
function holed(items: readonly Item[]): Item[] {
  const out: Item[] = new Array<Item>(items.length);
  for (let i = 0; i < items.length; i++) out[i] = items[i]!;
  return out;
}
function kinds(list: List): number {
  let s = 0;
  for (const item of list.items) s += item.kind;
  return s;
}
console.log(kinds(new List(0, holed([new Item(1), new Item(2)]))));
`,
  );
  expect(ok).toBe(true);
  const kinds = body("kinds", llvm);
  expect(kinds).not.toBe("");
  expect(kinds).not.toContain("scr_arr_state");
  // Only an index outside the count makes an array, for the runtime getter.
  for (const block of kinds.split(/\n(?=\S)/).filter((b) => b.includes("scr_arr_view_cref(")))
    expect(block.startsWith("inl.get.miss")).toBe(true);
});

test.runIf(lowRegion)("a read that escapes gives an array of the elements", async () => {
  const { ok, llvm } = await build(
    classes +
      `
function count(items: readonly Item[]): number {
  return items.length;
}
function use(list: List): number {
  return count(list.items) + list.items.indexOf(list.items[0]!);
}
console.log(use(new List(0, [new Item(1)])));
`,
  );
  expect(ok).toBe(true);
  expect(body("use", llvm)).toContain("call ptr @scr_arr_view_cref(");
});

test("writes to the arrays fields hold are refused", async () => {
  for (const write of [
    // Through a read of the field.
    `function grow(list: List): void {
  (list.items as Item[]).push(new Item(5));
}
grow(new List(0, [new Item(1)]));`,
    // Through a parameter and an array element.
    `function clear(items: readonly Item[]): void {
  (items as Item[]).length = 0;
}
const all = [new List(0, [new Item(1)]).items];
clear(all[0]!);`,
    // Through a Map value.
    `const byPos = new Map<number, readonly Item[]>();
const list = new List(0, [new Item(1)]);
byPos.set(list.pos, list.items);
(byPos.get(0)! as Item[])[0] = new Item(2);`,
  ]) {
    const result = await build(classes + write);
    expect(result.ok).toBe(false);
    expect(result.codes).toContain("SC7009");
    expect(result.messages.join("\n")).toContain(
      "writes to an array that may be an InlineArray field's",
    );
  }
});

test("a write names the field read whose array it may reach", async () => {
  const result = await build(
    classes +
      `
function same(items: readonly Item[]): readonly Item[] {
  return items;
}
const list = new List(0, [new Item(1)]);
const all: (readonly Item[])[] = [same(list.items)];
(all[0]! as Item[]).pop();
`,
  );
  expect(result.ok).toBe(false);
  expect(result.messages.join("\n")).toMatch(
    /writes to an array that may be an InlineArray field's \(from main\.ts:\d+:\d+\)/,
  );
});

test("other arrays of the element type stay writable", async () => {
  // Arrays are followed by where they are held, not by type: a helper that
  // returns its argument gives each caller its own array back.
  const result = await build(
    classes +
      `
function same(items: readonly Item[]): readonly Item[] {
  return items;
}
const list = new List(0, [new Item(1)]);
const views: (readonly Item[])[] = [same(list.items)];
const scratch: Item[][] = [[]];
const own = same([new Item(2)]) as Item[];
scratch[0]!.push(new Item(3));
own.push(new Item(4));
console.log(views[0]!.length, scratch[0]!.length, own.length);
`,
  );
  expect(result.messages).toEqual([]);
});

test("a read of the field may reach printing and copies, but no other library call", async () => {
  const reads = await build(
    classes +
      `
const list = new List(0, [new Item(1)]);
console.log(list.items, JSON.stringify(list.items), [...list.items].length);
console.log(new List(1, list.items.slice()).items.length);
`,
  );
  expect(reads.ok).toBe(true);
  const frozen = await build(
    classes +
      `
console.log(Object.isFrozen(new List(0, [new Item(1)]).items));
`,
  );
  expect(frozen.ok).toBe(false);
  expect(frozen.messages.join("\n")).toContain("reaches the library call");
});

test("the constructor is passed an array nothing else keeps", async () => {
  const accepted = [
    // A literal, a copy, and a factory's result.
    `function fresh(n: number): Item[] {
  const out: Item[] = [];
  for (let i = 0; i < n; i++) out.push(new Item(i));
  return out;
}
const a = new List(0, [new Item(1)]);
const b = new List(1, a.items.concat([new Item(2)]));
console.log(a.items.length, b.items.length, new List(2, fresh(3)).items.length);`,
    // A local's last use, after writes in place, in either arm of a
    // conditional, and after an early return.
    `function make(c: boolean): List {
  const items = [new Item(1)];
  items.push(new Item(2));
  if (items.length > 5) return new List(-1, items);
  return c ? new List(0, items) : new List(1, items);
}
console.log(make(true).items.length, make(false).pos);`,
    // A parameter its callers move.
    `function wrap(pos: number, items: Item[]): List {
  items.reverse();
  return new List(pos, items);
}
function build(n: number): List {
  return wrap(n, Array.from({ length: n }, (_, i) => new Item(i)));
}
console.log(build(2).items[0]!.kind);`,
    // An array a field already holds.
    `const a = new List(0, [new Item(1)]);
const shared = a.items;
console.log(new List(1, shared).items.length, new List(2, shared).pos);`,
    // An array that is never written, shared by several constructors.
    `const none: Item[] = [];
function make(items: Item[]): List {
  return new List(0, items.length === 0 ? none : items);
}
const lists: List[] = [];
for (let i = 0; i < 2; i++) lists.push(new List(i, none));
console.log(lists.length, make([]).items.length, make([new Item(1)]).items.length);`,
    // A local that each pass of a loop moves and then replaces.
    `function pairs(n: number): List[] {
  const lists: List[] = [];
  let items: Item[] = [];
  for (let i = 0; i < n; i++) {
    items.push(new Item(i));
    if (i % 2 === 1) {
      lists.push(new List(i, items));
      items = [];
    }
  }
  return lists;
}
console.log(pairs(4).length);`,
    // A top-level array, read elsewhere.
    `const items = [new Item(1), new Item(2)];
function count(): number {
  return items.length;
}
console.log(count());
const list = new List(0, items);
console.log(list.items.length);`,
  ];
  for (const source of accepted) {
    const result = await build(classes + source);
    expect(result.messages).toEqual([]);
  }
  const refused = [
    // Written after the move.
    `const items = [new Item(1)];
const list = new List(0, items);
items.push(new Item(2));
console.log(list.items.length);`,
    // Kept in another variable.
    `const items = [new Item(1)];
const kept = items;
const list = new List(0, items);
kept.push(new Item(2));
console.log(list.items.length);`,
    // A parameter whose caller keeps the array.
    `function wrap(items: Item[]): List {
  return new List(0, items);
}
const items = [new Item(1)];
const list = wrap(items);
items.push(new Item(2));
console.log(list.items.length);`,
    // A parameter of another class's constructor, and of a method.
    `class Section {
  readonly list: List;
  constructor(items: Item[]) {
    this.list = new List(0, items);
  }
}
const items = [new Item(1)];
const section = new Section(items);
items.push(new Item(2));
console.log(section.list.items.length);`,
    `class Maker {
  make(items: Item[]): List {
    return new List(0, items);
  }
}
class FlagMaker extends Maker {
  override make(items: Item[]): List {
    return new Flagged(0, items, 1);
  }
}
function run(maker: Maker): number {
  const items = [new Item(1)];
  const list = maker.make(items);
  items.push(new Item(2));
  return list.items.length;
}
console.log(run(new Maker()), run(new FlagMaker()));`,
    // A shared array written elsewhere.
    `const none: Item[] = [];
const a = new List(0, none);
const b = new List(1, none);
function add(items: Item[]): void {
  items.push(new Item(2));
}
add(none);
console.log(a.items.length, b.items.length);`,
    // A function returning a shared array.
    `const all: Item[] = [new Item(1)];
function current(): Item[] {
  return all;
}
const list = new List(0, current());
all.push(new Item(2));
console.log(list.items.length);`,
  ];
  for (const source of refused) {
    const result = await build(classes + source);
    expect(result.ok).toBe(false);
    expect(result.codes).toContain("SC7009");
    expect(result.messages.join("\n")).toContain("may be kept elsewhere");
  }
});

test("an InlineArray field must keep its contract", async () => {
  const twice = await build(`
class Item implements ProgramLifetime {}
class List implements ProgramLifetime {
  readonly items: InlineArray<Item>;
  constructor(items: readonly Item[], more: readonly Item[]) {
    this.items = items;
    if (more.length > 0) (this as { items: readonly Item[] }).items = more;
  }
}
console.log(new List([new Item()], []).items.length);
`);
  expect(twice.ok).toBe(false);
  expect(twice.codes).toContain("SC7009");

  const mortal = await build(`
class Item implements ProgramLifetime {}
class List {
  readonly items: InlineArray<Item>;
  constructor(items: readonly Item[]) {
    this.items = items;
  }
}
console.log(new List([new Item()]).items.length);
`);
  expect(mortal.ok).toBe(false);
  expect(mortal.codes).toContain("SC7009");
  expect(mortal.messages.join("\n")).toContain("not ProgramLifetime");

  const computed = await build(`
class Item implements ProgramLifetime {}
class List implements ProgramLifetime {
  readonly items: InlineArray<Item>;
  constructor(n: number) {
    const items: Item[] = [];
    for (let i = 0; i < n; i++) items.push(new Item());
    this.items = items;
  }
}
console.log(new List(2).items.length);
`);
  expect(computed.ok).toBe(false);
  expect(computed.codes).toContain("SC7009");
  expect(computed.messages.join("\n")).toContain("constructor parameter");
});

test.runIf(lowRegion)(
  "an instance inside a dynamic value shows the field as an array",
  async () => {
    const { ok, llvm } = await build(
      classes +
        `
class Holder {
  readonly list: List;
  constructor(list: List) {
    this.list = list;
  }
}
const list = new List(3, [new Item(1), new Item(2)]);
console.log(JSON.stringify({ list }), JSON.stringify(new Holder(list)));
`,
    );
    expect(ok).toBe(true);
    // The instance's dynamic view reads the field as an array of the elements.
    const views = llvm
      .split(/\n(?=define )/)
      .filter((f) => f.startsWith("define") && f.includes("_materialize("));
    expect(views.some((f) => f.includes("call ptr @scr_arr_view_cref("))).toBe(true);
  },
);

test("the constructor stores the array parameter and does nothing else with it", async () => {
  const result = await build(`
class Item implements ProgramLifetime {}
class List implements ProgramLifetime {
  readonly items: InlineArray<Item>;
  readonly count: number;
  constructor(items: Item[]) {
    items.push(new Item());
    this.items = items;
    this.count = items.length;
  }
}
console.log(new List([new Item()]).count);
`);
  expect(result.ok).toBe(false);
  expect(result.codes).toContain("SC7009");
  expect(result.messages.join("\n")).toContain("besides storing it in the field");
});

test("a read of an InlineArray field is not compared by identity", async () => {
  const result = await build(`
class Item implements ProgramLifetime {}
class List implements ProgramLifetime {
  readonly items: InlineArray<Item>;
  constructor(items: readonly Item[]) {
    this.items = items;
  }
}
const items = [new Item()];
const list = new List(items);
console.log(list.items === items);
`);
  expect(result.ok).toBe(false);
  expect(result.codes).toContain("SC7009");
  expect(result.messages.join("\n")).toContain("compared by identity");
});

test("InlineArray is checked on instance fields only", async () => {
  const result = await build(`
class Item implements ProgramLifetime {}
function count(items: InlineArray<Item>): number {
  return items.length;
}
console.log(count([new Item()]));
`);
  expect(result.ok).toBe(false);
  expect(result.codes).toContain("SC7006");
});