Bun gets a new bundler (#2312)

* alright now just gotta try running it

* fix a gajillion compiler errors

* even more code

* okay i fixed more errors

* wip

* Update launch.json

* Update string_builder.zig

* `fast_debug_build_mode` makes debug build 2x faster

* Update bundle_v2.zig

* more code!

* It bundles!

* Rename `Bun.Transpiler` to `Bun.Bundler`

* `import()` expressions almost work

* wip attempt to get import() expr to work

* Bundle namespace imports

* Attempt to fix the issue with import() unsuccessfully

* consider current working directory when resolving relative paths (#2313)

* consider current working directory when resolving relative paths

fixes #2298

* comment test

---------

Co-authored-by: Jarred Sumner <709451+Jarred-Sumner@users.noreply.github.com>

* support `expect().toThrow(/pattern/)` (#2314)

- fix time-zone-dependent test failure

* fix missing `Blob` error messages on Linux (#2315)

* fix & clean up tests (#2318)

- skip flaky tests when running as `root`
- use `expect().toThrow()`
- clean up temporary files after tests

* feat(tty): add some `tty.WriteStream` methods to `process.{stdout, stderr}` (#2320)

* feat(stdio): add some `tty.WriteStream` methods

* chore(builtins): add process builtin gen'd code

* Fix docker install command

* `bun test` on macOS in GitHub Actions (#2322)

* Fixes #2323

* throw invalid parameter errors in `crypto.scryptSync` (#2331)

* throw invalid parameter errors

* remove comptime, add empty buffer function

* remove error_name comptime

* Add reference documentation for bun:test (#2327)

* Reorganize tests (#2332)

* Fix html-rewriter.test.js

* fix the wrong thing being incremented in hmr example (#2334)

* Add more test harness

* Improve Benchmarking page, small fixes (#2339)

* Improve benchmarking page

* WIP

* Add typescript instructions to hot

* Document preload in Plugins. Fix loader in plugin types.

* Fix typo

* Fix links

* run prettier

* Document openInEditor

* improve `Buffer` compatibility with Node.js (#2341)

* improve `Buffer` compatibility with Node.js

* use `memmove()`
allow `encoding` to be `undefined`

* run `bun test` after macOS builds (#2343)

* "binary" is an alias of "latin1"

Fixes https://github.com/oven-sh/bun/issues/2110

* More spec compliant `Blob.prototype.type` (#2340)

* Make `Blob.prototype. type` more spec compliant

* Add a few more checks for isNumber()

* Fix `make headers`

* Safer JSValue.isString()

* More tests for blob.slice

* Make `Blob.prototype.type` more spec compliant

* Add isASCII check

* Fix types

* Fix failing type test

* Update blob.zig

* Update blob.zig

* Fix .eql check on empty values

---------

Co-authored-by: Jarred Sumner <709451+Jarred-Sumner@users.noreply.github.com>

* Fix bug in test runner

* Support `import()` expressions

* Implement `require()`

* clean up bit_set.zig slightly

* Move some things around

* misc cleanup

* Cleanup some things

* Fix a lot of stuff

* Fix `module.exports.fn = fn;` in ESM entry point

* Fix crash due when printing file

* Fix issue with class names

* Fix issue with `export default identifier`

* Update js_parser.zig

* optimization: inline single-property object acceses and arrays

* Fix undefined memory in renamed symbols list

* Handle call target

* wip

* Inline it

* Fix undefined memory issue when reclaiming blocks in ast

* Halt linking on any parse errors

* alias

* Rename `enable_bundling` to `enable_legacy_bundling`

* Workaround anonymous struct literal zig bug

* Use slower approach (without bitset) because it doesn't break after 8 symbols

* Fix incorrectly-renaming statically defined symbols

* Handle more edgecases in our bit_set fork

* Reduce number of allocations for `define`

* Do not rename unbound symbols

* Clean up dot defines a little more

* Make the generated names prettier

* Workaround runtime symbol missing issue

* Fail the build on errors

* Support export * from

* Support `--outfile`

* partially fix renaming

* fanicer symbol renaming impl

* misc, extremely revertible cleanup

* Fix up some bugs with symbol renaming

* formatting

* Update launch.json

* Parse `__PURE__` comments

* clean up simd code for pure comments

* changes to merge

* workaround runtime issue

* Fix issue with `export * as` not propagating correctly

* Make all top-level declarations `var` when bundling

* Fix missing prefix

* Fix assigning to stack copy

* Fix missing runtime symbol

* Fix bug with namespace exports

* Dramatically reduce allocations

* Update launch.json

* Add missing flags

* Update js_parser.zig

* small cleanup

* Make the export name better

* Fix unnecessary `var foo = foo`

* Implement CommonJS -> ESM conversion

* Implement module redirects

* Port esbuild bundler tests for new bundler (#2380)

* started porting esbuild tests

* clean up test names and api before moving on

* port tests using a program i wrote

* replace todo generated comment

* fix generated tests not including some files

* work on tests

* [github web editor] add define, external, inject, minifySyntax, minifyWhitespace options.

* get most of the todo comments out of the way, but expectBundled does not handle most of the cases

* continue working on esbuild tests

* use test.skip for unsupported tests

* Fixups for test runner

* Hoist imports & exports

* Fix test

* Hoist classes

* bundler test refining, 51/835

* Fix runtime require

* bundler test refining, 81/835

* bundler test refining, 93/835

* Make the test work in any timezone

* feat(expect): update toBeInstanceOf (#2396)

* feat: update instanceof binding

* fix: according to PR comments

* Rename `expectObjectTypeCount` to `expectMaxObjectTypeCount`

* Fix socket tests with connection errors (#2403)

* release pending activity with connection error handler

* unref poll_ref

* remove trailing comma

* Organize Dockerfiles for official status

* Remove test Dockerfile

* Remove old Docker workflow

* Feat(test): add toMatch (#2404)

* Fix various fetch/response/request tests (#2416)

* fix most fetch tests, skip a few

* fastGet, toValueGC, and invalid init

* bigint unreachable, range error, log process as process

* remove extra fetch_headers

* remove js_type parameter, check isObject()

* throw invalid mime type error, use enum literal

* switch back to promise rejection

* RangeError pascal case

* Fix several bugs (#2418)

* utf16 codepoint with replacement character

* Fix test failure with `TextEncoder("ascii')`

* Add missing type

* Fix Response.prototype.bodyUsed and Request.prototype.bodyUsed

* Fix bug with scrypt error not clearing

* Update server.zig

* oopsie

* :nail_care:

* docs: Use correct url in the 'Issues' link in README header (#2420)

* Fix crash when rendering error page and the server or network is slow

* [fetch] Make the default body value `null` when unspecified

This is better aligned with the fetch spec

* Make node-net tests less flaky

* [node:net] Fix issue with `listen` callback firing before it's listening

* Always clear timers in node test harness

* Fix out of bounds access

Repro'd in Buffer tests

* Update UWS

cc @cirospaciari

* Make this test more thorough

* Hanging abort test

* 0 length body is a null stream

* Several bug fixes (#2427)

* Fix test

* Fix segfault when unexpected type is passed in `expect().toThrow`

* Fix issues with request constructor

* Don't bother cloning headers when its empty

* woops

* more tests

* fix incorrect test

* Make the fetch error messages better

* Update response.zig

* Fix test that failed on macOS

* Fix test

* Remove extra hash table lookups

* Support running dummy registry directly

cc @alexlamsl

* Update test

* Update test

* fixup

* Workaround crash in test runner

* Fixup test

* Fixup test

* Update os.test.js

---------

Co-authored-by: Jarred Sumner <709451+Jarred-Sumner@users.noreply.github.com>

* Remove usages of port numbers in tests

* Set -O2 and -fno-rtti

* Remove -g

* Prevent undefined memory access

* [bun test] Implement `--rerun-each` flag to run each test N times

* Reduce number of module scopes created

* add some extra abort checks into streams (#2430)

* add some checks to avoid UAF

* avoid multiple calls to finalize if endFromJS is called more than once

* fix no-op comment

* mark as requested_end on abort

* remove requested_end from abort

* remove unnecessary check (#2432)

* Fix bug with scoped aliased dependencies in bun install on macOS

* remove `addLog`, remove `--prominent-compile-errors`

* Finish the upgrade

* Optional chaining flag

* Implement same_target_becomes_destructuring optimization

* bundler test refining, 109/835

* Reset bindings

* Support multiple entry points

* Implement `--entry-names` flag

* Use a tempdir with a better name

* prettier

* Log file name

* Update js_parser.zig

* Mark all bun builtins as external

* Make resolve errors actually errors

* Update bundler_default.test.ts

* Fix `await import(foo)`

* WIP react server components

* Do more stuff at runtime

* :scissors:

* Support automatic JSX imports

* Use a module cache for now

* Update tsconfig.base.json

* Fix ThisOutsideFunctionNotRenamed

* woopsie

* moar cpu

* clamp it

* fixup

* Add a bunch of assertions

* Bun uses automatic runtime by default

* Parse Import Attributes

* Add a note about Valgrind

* Update developing.md

* Fix up code splitting for React Server Components

* Implement client component manifest

* Fix crash with --react-server-components and no client components

* Backport https://github.com/ziglang/zig/commit/4d31e3c917a05541394c544708f0047cfb53331a

* Update launch.json

* Fix for latest zig

* Workaround bug with ?[]const string

Occasionally saw alignment errors in this code

Workaround https://github.com/ziglang/zig/issues/15085

related: https://github.com/ziglang/zig/pull/15089

* switch to regular slice

* Avoid initializing named_imports and named_exports as undefined

* Reduce usages of `undefined`

* Add more assertions

* --watch wip

* Update javascript.zig

* Possibly fix the race condition

* Faster `do`

* bump allocator

* Reduce the size of `Symbol` slightly

* Alphabetically sort runtime import symbols, for determinism

* Prepare for code splitting

* handle overlapping stdout

* pure

* clean up some things

* Fix bug with `$$typeof`

* Address CommonJS -> ESM hoisting bug

* Support `"use server"` in manifest

* Implement `"use server"`

* Fix importing bun builtins when bundling

* Make `commonjs_to_esm` a feature flag, fix some splitting bugs

* :scissors:

* fixme remove this

* Fix crash in longestCommonPath

* Chunking! Just need to do import paths now.

* Import paths work...now trying to figure out how to make runtime symbols work

* add workaround

* Replace `bun bun` with `bun build`

* Fix crash with dual package hazard

* Fix many CommonJS <> ESM interop bugs

* Support package.json `"sideEffects"`

also skip loading unnecessary package.json data in `bun run`

* add a not good --watch implementation

* bundler test refining, 140/831

* remove accidentally committed file

* do not return status code 1 on successful bundles

* bundler test refining, 159/830

* pass exit code to exitOrWatch

* clean up help menu

-remove two spaces to line up bun build
-moved all <r> tags to the end of the text they are colorizing
-moved other colors to the start of the text they colorize
-removed unneeded <r> tags, keeping only one at the start of the block

* importstar is fully ported

* wip

* you can run code in this branch now

* Disable this transform

* organize and document bundler tests

* Fix double import

* Fix sloppy mode function declarations

* Disable our CommonJS transform for now

* add `assertNotPresent` to make splitting cases easier

* Bump!

* Update bun.d.ts

* use import.meta.require in runtime code

* Disable this again

* Fix dirname

* Fix ESM -> CJS wrapper

* :nail_care:

---------

Co-authored-by: Jarred Sumner <709451+Jarred-Sumner@users.noreply.github.com>
Co-authored-by: Alex Lam S.L <alexlamsl@gmail.com>
Co-authored-by: Derrick Farris <mr.dcfarris@gmail.com>
Co-authored-by: Ashcon Partovi <ashcon@partovi.net>
Co-authored-by: Dylan Conway <35280289+dylan-conway@users.noreply.github.com>
Co-authored-by: pfg <pfg@pfg.pw>
Co-authored-by: Colin McDonnell <colinmcd94@gmail.com>
Co-authored-by: dave caruso <me@paperdave.net>
Co-authored-by: zhiyuan <32867472+zhiyuang@users.noreply.github.com>
Co-authored-by: Dylan Conway <dylan.conway567@gmail.com>
Co-authored-by: Kamil Ogórek <kamil.ogorek@gmail.com>
Co-authored-by: Ciro Spaciari <ciro.spaciari@gmail.com>

1 files changed, 341 insertions, 0 deletions

diff --git a/src/util.zig b/src/util.zig
new file mode 100644
index 000000000..8e06df9a1
--- /dev/null
+++ b/src/util.zig
@@ -0,0 +1,341 @@
+// Things that maybe should go in Zig standard library at some point
+const std = @import("std");
+const bun = @import("bun");
+
+pub fn Key(comptime Map: type) type {
+    return FieldType(Map.KV, "key").?;
+}
+
+pub fn Value(comptime Map: type) type {
+    return FieldType(Map.KV, "value").?;
+}
+
+pub fn fromEntries(
+    comptime Map: type,
+    allocator: std.mem.Allocator,
+    comptime EntryType: type,
+    entries: EntryType,
+) !Map {
+    var map: Map = undefined;
+    if (@hasField(Map, "allocator")) {
+        map = Map.init(allocator);
+    } else {
+        map = Map{};
+    }
+
+    if (comptime std.meta.trait.isIndexable(EntryType)) {
+        if (comptime !needsAllocator(Map.ensureUnusedCapacity)) {
+            try map.ensureUnusedCapacity(entries.len);
+        } else {
+            try map.ensureUnusedCapacity(allocator, entries.len);
+        }
+
+        comptime var i: usize = 0;
+
+        inline while (i < std.meta.fields(EntryType).len) : (i += 1) {
+            map.putAssumeCapacity(entries[i].@"0", entries[i].@"1");
+        }
+
+        return map;
+    } else if (comptime std.meta.trait.isContainer(EntryType) and @hasDecl(EntryType, "count")) {
+        if (comptime !needsAllocator(Map.ensureUnusedCapacity)) {
+            try map.ensureUnusedCapacity(entries.count());
+        } else {
+            try map.ensureUnusedCapacity(allocator, entries.count());
+        }
+
+        if (comptime @hasDecl(EntryType, "iterator")) {
+            var iter = entries.iterator();
+            while (iter.next()) |entry| {
+                map.putAssumeCapacity(entry.@"0", entry.@"1");
+            }
+
+            return map;
+        }
+    } else if (comptime std.meta.trait.isContainer(EntryType) and std.meta.fields(EntryType).len > 0) {
+        if (comptime !needsAllocator(Map.ensureUnusedCapacity)) {
+            try map.ensureUnusedCapacity(std.meta.fields(EntryType).len);
+        } else {
+            try map.ensureUnusedCapacity(allocator, std.meta.fields(EntryType).len);
+        }
+
+        inline for (comptime std.meta.fieldNames(@TypeOf(EntryType))) |entry| {
+            map.putAssumeCapacity(entry.@"0", entry.@"1");
+        }
+
+        return map;
+    } else if (comptime std.meta.trait.isConstPtr(EntryType) and std.meta.fields(std.meta.Child(EntryType)).len > 0) {
+        if (comptime !needsAllocator(Map.ensureUnusedCapacity)) {
+            try map.ensureUnusedCapacity(std.meta.fields(std.meta.Child(EntryType)).len);
+        } else {
+            try map.ensureUnusedCapacity(allocator, std.meta.fields(std.meta.Child(EntryType)).len);
+        }
+
+        comptime var i: usize = 0;
+
+        inline while (i < std.meta.fields(std.meta.Child(EntryType)).len) : (i += 1) {
+            map.putAssumeCapacity(entries.*[i].@"0", entries.*[i].@"1");
+        }
+
+        return map;
+    }
+
+    @compileError("Cannot construct Map from entries of type " ++ @typeName(EntryType));
+}
+
+pub fn fromMapLike(
+    comptime Map: type,
+    allocator: std.mem.Allocator,
+    entries: anytype,
+) !Map {
+    var map: Map = undefined;
+    if (comptime @hasField(Map, "allocator")) {
+        map = Map.init(allocator);
+    } else {
+        map = Map{};
+    }
+
+    try map.ensureUnusedCapacity(entries.count());
+
+    var iter = entries.iterator();
+    while (iter.next()) |entry| {
+        map.putAssumeCapacityNoClobber(entry.key_ptr.*, entry.value_ptr.*);
+    }
+
+    return map;
+}
+
+pub fn FieldType(comptime Map: type, comptime name: []const u8) ?type {
+    const i = std.meta.fieldIndex(Map, name) orelse return null;
+    const field = std.meta.fields(Map)[i];
+    return field.field_type;
+}
+
+pub fn Of(comptime ArrayLike: type) type {
+    if (std.meta.trait.isSlice(ArrayLike)) {
+        return std.meta.Child(ArrayLike);
+    }
+
+    if (comptime @hasDecl(ArrayLike, "Elem")) {
+        return ArrayLike.Elem;
+    }
+
+    if (comptime @hasField(ArrayLike, "items")) {
+        return std.meta.Child(FieldType(ArrayLike, "items").?);
+    }
+
+    if (comptime @hasField(ArrayLike, "ptr")) {
+        return std.meta.Child(FieldType(ArrayLike, "ptr").?);
+    }
+
+    @compileError("Cannot infer type within " ++ @typeName(ArrayLike));
+}
+
+pub inline fn from(
+    comptime Array: type,
+    allocator: std.mem.Allocator,
+    default: anytype,
+) !Array {
+    const DefaultType = @TypeOf(default);
+    if (comptime std.meta.trait.isSlice(DefaultType)) {
+        return fromSlice(Array, allocator, DefaultType, default);
+    }
+
+    if (comptime std.meta.trait.isContainer(DefaultType)) {
+        if (comptime std.meta.trait.isContainer(Array) and @hasDecl(DefaultType, "put")) {
+            return fromMapLike(Array, allocator, default);
+        }
+
+        if (comptime @hasField(DefaultType, "items")) {
+            if (Of(FieldType(DefaultType, "items").?) == Of(Array)) {
+                return fromSlice(Array, allocator, @TypeOf(default.items), default.items);
+            }
+        }
+    }
+
+    if (comptime std.meta.trait.isContainer(Array) and @hasDecl(Array, "put")) {
+        if (comptime std.meta.trait.isConstPtr(DefaultType) and std.meta.fields(std.meta.Child(DefaultType)).len > 0) {
+            return fromEntries(Array, allocator, @TypeOf(default.*), default.*);
+        }
+        return fromEntries(Array, allocator, DefaultType, default);
+    }
+
+    if (comptime @typeInfo(DefaultType) == .Struct) {
+        return fromSlice(Array, allocator, DefaultType, default);
+    }
+
+    if (comptime @typeInfo(DefaultType) == .Array) {
+        return fromSlice(Array, allocator, []const Of(Array), @as([]const Of(Array), &default));
+    }
+
+    return fromSlice(Array, allocator, []const Of(Array), @as([]const Of(Array), default));
+}
+
+pub fn concat(
+    comptime T: type,
+    dest: []T,
+    src: []const []const T,
+) void {
+    var remain = dest;
+    for (src) |group| {
+        bun.copy(T, remain[0..group.len], group);
+        remain = remain[group.len..];
+    }
+}
+
+pub fn fromSlice(
+    comptime Array: type,
+    allocator: std.mem.Allocator,
+    comptime DefaultType: type,
+    default: DefaultType,
+) !Array {
+    var map: Array = undefined;
+    if (comptime std.meta.trait.isSlice(Array)) {} else if (comptime @hasField(Array, "allocator")) {
+        map = Array.init(allocator);
+    } else {
+        map = Array{};
+    }
+
+    // is it a MultiArrayList?
+    if (comptime !std.meta.trait.isSlice(Array) and @hasField(Array, "bytes")) {
+        try map.ensureUnusedCapacity(allocator, default.len);
+        for (default) |elem| {
+            map.appendAssumeCapacity(elem);
+        }
+
+        return map;
+    } else {
+        var slice: []Of(Array) = undefined;
+        if (comptime !std.meta.trait.isSlice(Array)) {
+            // is it an ArrayList with an allocator?
+            if (comptime !needsAllocator(Array.ensureUnusedCapacity)) {
+                try map.ensureUnusedCapacity(default.len);
+                // is it an ArrayList without an allocator?
+            } else {
+                try map.ensureUnusedCapacity(allocator, default.len);
+            }
+            if (comptime @hasField(Array, "items")) {
+                map.items.len = default.len;
+                slice = map.items;
+            } else if (comptime @hasField(Array, "len")) {
+                map.len = @intCast(u32, default.len);
+                slice = map.slice();
+            } else {
+                @compileError("Cannot set length of " ++ @typeName(Array));
+            }
+        } else if (comptime std.meta.trait.isSlice(Array)) {
+            slice = try allocator.alloc(Of(Array), default.len);
+        } else if (comptime @hasField(map, "ptr")) {
+            slice = try allocator.alloc(Of(Array), default.len);
+            map = .{
+                .ptr = slice.ptr,
+                .len = @truncate(u32, default.len),
+                .cap = @truncate(u32, default.len),
+            };
+        }
+
+        if (comptime std.meta.trait.isIndexable(DefaultType) and (std.meta.trait.isSlice(DefaultType) or std.meta.trait.is(.Array)(DefaultType))) {
+            var in = std.mem.sliceAsBytes(default);
+            var out = std.mem.sliceAsBytes(slice);
+            @memcpy(out.ptr, in.ptr, in.len);
+        } else {
+            @compileError("Needs a more specific type to copy from");
+        }
+
+        if (comptime std.meta.trait.isSlice(Array)) {
+            return @as(Array, slice);
+        }
+
+        return map;
+    }
+}
+
+/// Say you need to allocate a bunch of tiny arrays
+/// You could just do separate allocations for each, but that is slow
+/// With std.ArrayList, pointers invalidate on resize and that means it will crash.
+/// So a better idea is to batch up your allocations into one larger allocation
+/// and then just make all the arrays point to different parts of the larger allocation
+pub fn Batcher(comptime Type: type) type {
+    return struct {
+        head: []Type,
+
+        pub fn init(allocator: std.mem.Allocator, count: usize) !@This() {
+            var all = try allocator.alloc(Type, count);
+            return @This(){ .head = all };
+        }
+
+        pub inline fn done(this: *@This()) void {
+            std.debug.assert(this.head.len == 0);
+        }
+
+        pub inline fn eat(this: *@This(), value: Type) *Type {
+            return @ptrCast(*Type, &this.head.eat1(value).ptr);
+        }
+
+        pub inline fn eat1(this: *@This(), value: Type) []Type {
+            var prev = this.head[0..1];
+            prev[0] = value;
+            this.head = this.head[1..];
+            return prev;
+        }
+
+        pub inline fn next(this: *@This(), values: anytype) []Type {
+            this.head[0..values.len].* = values;
+            var prev = this.head[0..values.len];
+            this.head = this.head[values.len..];
+            return prev;
+        }
+    };
+}
+
+test "fromEntries" {
+    const values = try from(std.AutoHashMap(u32, u32), std.heap.page_allocator, .{
+        .{ 123, 456 },
+        .{ 789, 101112 },
+    });
+    const mapToMap = try from(std.AutoHashMap(u32, u32), std.heap.page_allocator, values);
+    try std.testing.expectEqual(values.get(123).?, 456);
+    try std.testing.expectEqual(values.get(789).?, 101112);
+    try std.testing.expectEqual(mapToMap.get(123).?, 456);
+    try std.testing.expectEqual(mapToMap.get(789).?, 101112);
+}
+
+test "from" {
+    const values = try from(
+        []const u32,
+        std.heap.page_allocator,
+        &.{ 1, 2, 3, 4, 5, 6 },
+    );
+    try std.testing.expectEqualSlices(u32, &.{ 1, 2, 3, 4, 5, 6 }, values);
+}
+
+test "from arraylist" {
+    const values = try from(
+        std.ArrayList(u32),
+        std.heap.page_allocator,
+        &.{ 1, 2, 3, 4, 5, 6 },
+    );
+    try std.testing.expectEqualSlices(u32, &.{ 1, 2, 3, 4, 5, 6 }, values.items);
+
+    const cloned = try from(
+        std.ArrayListUnmanaged(u32),
+        std.heap.page_allocator,
+        values,
+    );
+
+    try std.testing.expectEqualSlices(u32, &.{ 1, 2, 3, 4, 5, 6 }, cloned.items);
+}
+
+test "from arraylist with struct" {
+    const Entry = std.meta.Tuple(&.{ u32, u32 });
+    const values = try from(
+        std.ArrayList(Entry),
+        std.heap.page_allocator,
+        &.{ Entry{ 123, 456 }, Entry{ 123, 456 }, Entry{ 123, 456 }, Entry{ 123, 456 } },
+    );
+    try std.testing.expectEqualSlices(Entry, &[_]Entry{ .{ 123, 456 }, .{ 123, 456 }, .{ 123, 456 }, .{ 123, 456 } }, values.items);
+}
+
+fn needsAllocator(comptime Fn: anytype) bool {
+    return std.meta.fields(std.meta.ArgsTuple(@TypeOf(Fn))).len > 2;
+}