functionalscript · sergey-shandar · Aug 7, 2026 · Aug 7, 2026 · Aug 7, 2026 · Aug 7, 2026
diff --git a/fjs/asn.1/proof.f.ts b/fjs/asn.1/proof.f.ts
@@ -17,7 +17,7 @@ import {
     decodeObjectIdentifier,
     type ObjectIdentifier,
 } from "./module.f.ts"
-import { assert, assertEq } from '../asserts/module.f.ts'
+import { assert, assertEq } from '../asserts/module.f.mjs'
 
 const { concat, popFront: pop, listToVec } = msb
 const pop8 = pop(8n)

diff --git a/fjs/asserts/module.f.ts → fjs/asserts/module.f.mjs b/fjs/asserts/module.f.ts → fjs/asserts/module.f.mjs
@@ -6,24 +6,29 @@
 
 /**
  * Marks a code path as unimplemented. Always throws.
+ * @type {() => never}
  */
-export const todo = (): never => { throw 'not implemented' }
+export const todo = () => { throw 'not implemented' }
 
 /**
  * Throws `msg` (default `'assertion failed'`) if `v` is `false`.
  *
  * Narrows `v` to `true` via `asserts v`, so callers can rely on the
  * condition holding for the rest of the enclosing scope.
+ *
+ * @type {(v: boolean, msg?: unknown) => asserts v}
  */
-export const assert: (v: boolean, msg?: unknown) => asserts v = (v, msg = 'assertion failed') => {
+export const assert = (v, msg = 'assertion failed') => {
     if (!v) throw msg
 }
 
 /**
  * Asserts that `a` and `b` are `===`, throwing `x` (the `[a, b]` pair, plus
  * an optional third element used as an extra message) if they differ.
+ *
+ * @type {<T>(...x: readonly[T, T, unknown?]) => void}
  */
-export const assertEq = <T>(...x: readonly[T, T, unknown?]): void => {
+export const assertEq = (...x) => {
     const [a, b] = x
     assert(a === b, x)
 }
@@ -32,8 +37,10 @@ export const assertEq = <T>(...x: readonly[T, T, unknown?]): void => {
  * Compile-time-only check: a type resolves only if it is exactly `true`.
  * Used to assert type-level properties without any runtime cost, e.g.
  * `type _ = Assert<Equal<A, B>>`.
+ *
+ * @template {true} T
+ * @typedef {T} Assert
  */
-export type Assert<T extends true> = T
 
 /**
  * Asserts that `a` is neither `null` nor `undefined` and returns it,
@@ -42,8 +49,10 @@ export type Assert<T extends true> = T
  * Use this to chain directly off a call that may return a nullish value,
  * e.g. `const r = assertNotNullish(f(x))`. For a variable that already
  * exists, prefer `assert(a !== null && a !== undefined)` instead.
+ *
+ * @type {<T>(a: T|null|undefined, msg?: unknown) => T}
  */
-export const assertNotNullish = <T>(a: T|null|undefined, msg?: unknown): T => {
+export const assertNotNullish = (a, msg) => {
     assert(a !== null && a !== undefined, msg)
     return a
 }
diff --git a/fjs/asserts/proof.f.ts b/fjs/asserts/proof.f.ts
@@ -1,4 +1,4 @@
-import { assert, assertEq, todo } from './module.f.ts'
+import { assert, assertEq, todo } from './module.f.mjs'
 
 export const proof = {
     assertPassesOnTrue: () => {

diff --git a/fjs/base_n/proof.f.ts b/fjs/base_n/proof.f.ts
@@ -1,4 +1,4 @@
-import { assertEq } from '../asserts/module.f.ts'
+import { assertEq } from '../asserts/module.f.mjs'
 import { empty, maxLength, vec, length } from '../types/bit_vec/module.f.ts'
 import { baseN } from './module.f.ts'
 

diff --git a/fjs/basen/base64/proof.f.ts b/fjs/basen/base64/proof.f.ts
@@ -1,4 +1,4 @@
-import { assertEq } from '../../asserts/module.f.ts'
+import { assertEq } from '../../asserts/module.f.mjs'
 import { empty, vec, repeat, vec8, maxLength, type Vec } from "../../types/bit_vec/module.f.ts"
 import { encode, decode } from "./module.f.ts"
 

diff --git a/fjs/basen/cbase32/proof.f.ts b/fjs/basen/cbase32/proof.f.ts
@@ -1,6 +1,6 @@
 import { empty, vec, type Vec } from "../../types/bit_vec/module.f.ts"
 import { cBase32ToVec, cBase32ToVec5x, vec5xToCBase32, vecToCBase32 } from "./module.f.ts"
-import { assertEq } from '../../asserts/module.f.ts'
+import { assertEq } from '../../asserts/module.f.mjs'
 
 const check5x = (s: string, v: Vec) => {
     const sr = vec5xToCBase32(v)

diff --git a/fjs/bnf/data/proof.f.ts b/fjs/bnf/data/proof.f.ts
@@ -4,7 +4,7 @@ import { sort } from '../../types/object/module.f.ts'
 import { oneEncode, option, range, rangeDecode, repeat0Plus, set } from '../module.f.ts'
 import { classic, deterministic } from '../testlib.f.ts'
 import { emptyTagMap, type RuleSet, toData } from './module.f.ts'
-import { assertEq } from '../../asserts/module.f.ts'
+import { assertEq } from '../../asserts/module.f.mjs'
 
 export const proof = {
     rangeDecode: () => {

diff --git a/fjs/bnf/descent/proof.f.ts b/fjs/bnf/descent/proof.f.ts
@@ -4,7 +4,7 @@ import { commaJoin0Plus, option, range, repeat0Plus, set } from '../module.f.ts'
 import { deterministic } from '../testlib.f.ts'
 import { emptyTagMap, toData } from '../data/module.f.ts'
 import { descentParser, type DescentMatch, type CodePointMeta, type DescentMatchResult } from './module.f.ts'
-import { assertEq, assertNotNullish } from '../../asserts/module.f.ts'
+import { assertEq, assertNotNullish } from '../../asserts/module.f.mjs'
 
 const mapCodePoint = (cp: CodePoint): CodePointMeta<unknown> => [cp, undefined]
 

diff --git a/fjs/bnf/ll1/proof.f.ts b/fjs/bnf/ll1/proof.f.ts
@@ -4,7 +4,7 @@ import { commaJoin0Plus, option, range, repeat0Plus, set } from '../module.f.ts'
 import { deterministic } from '../testlib.f.ts'
 import { type RuleSet, toData } from '../data/module.f.ts'
 import { dispatchMap, type MatchResult, parser, parserRuleSet } from './module.f.ts'
-import { assertEq } from '../../asserts/module.f.ts'
+import { assertEq } from '../../asserts/module.f.mjs'
 
 export const proof = {
     dispatch: [

diff --git a/fjs/bnf/module.f.ts b/fjs/bnf/module.f.ts
@@ -11,7 +11,7 @@ import { definedValues, type StringMap } from '../types/object/module.f.ts'
 import { type Array2, isArray2 } from '../types/array/module.f.ts'
 import { map, toArray, repeat as listRepeat } from '../types/list/module.f.ts'
 import { contains } from '../types/range/module.f.ts'
-import { assert } from '../asserts/module.f.ts'
+import { assert } from '../asserts/module.f.mjs'
 
 // Types
 

diff --git a/fjs/bnf/proof.f.ts b/fjs/bnf/proof.f.ts
@@ -1,4 +1,4 @@
-import { assert, assertEq } from '../asserts/module.f.ts'
+import { assert, assertEq } from '../asserts/module.f.mjs'
 import { classic, deterministic } from './testlib.f.ts'
 import {
     rangeEncode,

diff --git a/fjs/bnf/token_symbol/module.f.ts b/fjs/bnf/token_symbol/module.f.ts
@@ -8,7 +8,7 @@
  *
  * @module
  */
-import { assert } from '../../asserts/module.f.ts'
+import { assert } from '../../asserts/module.f.mjs'
 import { fromUndefined, type Nullable } from '../../types/nullable/module.f.ts'
 import { eof, rangeDecode, unicodeRange } from '../module.f.ts'
 

diff --git a/fjs/bnf/token_symbol/proof.f.ts b/fjs/bnf/token_symbol/proof.f.ts
@@ -1,4 +1,4 @@
-import { assertEq } from '../../asserts/module.f.ts'
+import { assertEq } from '../../asserts/module.f.mjs'
 import { capacity, encoding } from './module.f.ts'
 
 const names = ['>>', '>>>=', 'instanceof'] as const

diff --git a/fjs/cas/cli/proof.f.ts b/fjs/cas/cli/proof.f.ts
@@ -5,7 +5,7 @@ import { defaultNodeProgramOptions, emptyState, virtual } from '../../effects/no
 import { type NodeProgramOptions } from '../../effects/node/module.f.ts'
 import { dispatch } from '../../cli/module.f.ts'
 import { vecToCBase32 } from '../../basen/cbase32/module.f.ts'
-import { assert, assertEq } from '../../asserts/module.f.ts'
+import { assert, assertEq } from '../../asserts/module.f.mjs'
 
 const makeOptions = (args: readonly string[]): NodeProgramOptions =>
     ({ ...defaultNodeProgramOptions, args })

diff --git a/fjs/cas/evo/proof.f.ts b/fjs/cas/evo/proof.f.ts
@@ -1,4 +1,4 @@
-import { assert, assertEq } from '../../asserts/module.f.ts'
+import { assert, assertEq } from '../../asserts/module.f.mjs'
 import { pure } from '../../effects/module.f.ts'
 import { fileCas, type Cas } from '../module.f.ts'
 import { sha256 } from '../../crypto/sha2/module.f.ts'

diff --git a/fjs/cas/proof.f.ts b/fjs/cas/proof.f.ts
@@ -8,7 +8,7 @@ import { error, ok, type Ok } from '../types/result/module.f.ts'
 import { emptyState, virtual } from '../effects/node/virtual/module.f.ts'
 import { join } from '../path/module.f.ts'
 import { nonEmpty, empty, type List } from '../effects/list/module.f.ts'
-import { assert, assertEq, assertNotNullish } from '../asserts/module.f.ts'
+import { assert, assertEq, assertNotNullish } from '../asserts/module.f.mjs'
 
 const testDir = './test-cas-cli'
 

diff --git a/fjs/ci/deno/proof.f.ts b/fjs/ci/deno/proof.f.ts
@@ -1,6 +1,6 @@
 import { coverageInclude, denoSteps } from './module.f.ts'
 import { toSteps } from '../common/module.f.ts'
-import { assert, assertEq } from '../../asserts/module.f.ts'
+import { assert, assertEq } from '../../asserts/module.f.mjs'
 
 const coverageRuns = (version: string): readonly string[] =>
     toSteps(denoSteps(version))

diff --git a/fjs/ci/nix/proof.f.ts b/fjs/ci/nix/proof.f.ts
@@ -3,7 +3,7 @@
  *
  * @module
  */
-import { assert, assertEq } from '../../asserts/module.f.ts'
+import { assert, assertEq } from '../../asserts/module.f.mjs'
 import { step } from '../../effects/module.f.ts'
 import { readUtf8File } from '../../effects/node/module.f.ts'
 import { emptyState, virtual } from '../../effects/node/virtual/module.f.ts'

diff --git a/fjs/ci/node/proof.f.ts b/fjs/ci/node/proof.f.ts
@@ -1,6 +1,6 @@
 import { basicNode } from './module.f.ts'
 import { test } from '../common/module.f.ts'
-import { assertEq } from '../../asserts/module.f.ts'
+import { assertEq } from '../../asserts/module.f.mjs'
 
 export const proof = {
     basicNode: () => {

diff --git a/fjs/ci/proof.f.ts b/fjs/ci/proof.f.ts
@@ -5,7 +5,7 @@ import { coverageInclude } from './deno/module.f.ts'
 import { utf8, utf8ToString } from '../text/module.f.ts'
 import { empty as emptyVec, isVec } from '../types/bit_vec/module.f.ts'
 import { type MetaStep, type Os, test, ubuntu, type GitHubAction, parseGitHubAction } from './common/module.f.ts'
-import { assert, assertEq } from '../asserts/module.f.ts'
+import { assert, assertEq } from '../asserts/module.f.mjs'
 import type { State } from '../effects/node/virtual/module.f.ts'
 import { emptyState, virtual, type Dir } from '../effects/node/virtual/module.f.ts'
 import { parse as jsonParse } from '../media/json/module.f.ts'

diff --git a/fjs/cli/proof.f.ts b/fjs/cli/proof.f.ts
@@ -2,7 +2,7 @@ import { pure } from '../effects/module.f.ts'
 import type { NodeOp, NodeProgramOptions } from '../effects/node/module.f.ts'
 import { defaultNodeProgramOptions, emptyState, virtual } from '../effects/node/virtual/module.f.ts'
 import { dispatch, type Commands } from './module.f.ts'
-import { assert, assertEq } from '../asserts/module.f.ts'
+import { assert, assertEq } from '../asserts/module.f.mjs'
 
 const makeOptions = (args: readonly string[]): NodeProgramOptions =>
     ({ ...defaultNodeProgramOptions, args })

diff --git a/fjs/common/monoid/proof.f.ts b/fjs/common/monoid/proof.f.ts
@@ -1,5 +1,5 @@
 import { repeat, fold, type Monoid } from "./module.f.ts";
-import { assertEq } from '../../asserts/module.f.ts'
+import { assertEq } from '../../asserts/module.f.mjs'
 
 export const proof = {
     numberAdd: () => {

diff --git a/fjs/crypto/hmac/proof.f.ts b/fjs/crypto/hmac/proof.f.ts
@@ -1,4 +1,4 @@
-import { assertEq } from '../../asserts/module.f.ts'
+import { assertEq } from '../../asserts/module.f.mjs'
 import { utf8 } from '../../text/module.f.ts'
 import { uint, vec } from '../../types/bit_vec/module.f.ts'
 import { sha256, sha384, sha512 } from '../sha2/module.f.ts'

diff --git a/fjs/crypto/pow/proof.f.ts b/fjs/crypto/pow/proof.f.ts
@@ -2,7 +2,7 @@ import { utf8 } from '../../text/module.f.ts'
 import { empty, uint } from '../../types/bit_vec/module.f.ts'
 import { computeSync, sha224, sha256 } from '../sha2/module.f.ts'
 import { bitcoinPow, genesisNBits, genesisTarget, pow, sha256Pow, targetFromNBits } from './module.f.ts'
-import { assert, assertEq, assertNotNullish } from '../../asserts/module.f.ts'
+import { assert, assertEq, assertNotNullish } from '../../asserts/module.f.mjs'
 
 const p256 = sha256Pow
 const p224 = pow(sha224)

diff --git a/fjs/crypto/secp/proof.f.ts b/fjs/crypto/secp/proof.f.ts
@@ -1,4 +1,4 @@
-import { assert, assertEq, assertNotNullish } from '../../asserts/module.f.ts'
+import { assert, assertEq, assertNotNullish } from '../../asserts/module.f.mjs'
 import { prime_field } from '../../types/prime_field/module.f.ts'
 import { curve, secp256k1, secp192r1, secp256r1, eq, type Point, secp384r1, secp521r1, type Curve, type Init } from './module.f.ts'
 

diff --git a/fjs/crypto/sha2/proof.f.ts b/fjs/crypto/sha2/proof.f.ts
@@ -1,7 +1,7 @@
 import { utf8 } from '../../text/module.f.ts'
 import { repeat, uint, vec } from '../../types/bit_vec/module.f.ts'
 import { flip } from '../../types/function/module.f.ts'
-import { assertEq } from '../../asserts/module.f.ts'
+import { assertEq } from '../../asserts/module.f.mjs'
 import { map } from '../../types/list/module.f.ts'
 import {
     base32,

diff --git a/fjs/crypto/sign/module.f.ts b/fjs/crypto/sign/module.f.ts
@@ -3,7 +3,7 @@
  *
  * @module
  */
-import { assertNotNullish } from '../../asserts/module.f.ts'
+import { assertNotNullish } from '../../asserts/module.f.mjs'
 import type { Array2 } from '../../types/array/module.f.ts'
 import { bitLength, divUp8, roundUp8 } from '../../types/bigint/module.f.ts'
 import { empty, length, msb, repeat, unpack, vec, vec8, type Vec } from '../../types/bit_vec/module.f.ts'

diff --git a/fjs/crypto/sign/proof.f.ts b/fjs/crypto/sign/proof.f.ts
@@ -5,7 +5,7 @@ import { hmac } from "../hmac/module.f.ts"
 import { secp192r1, secp256r1, secp384r1, secp521r1, type Curve } from "../secp/module.f.ts"
 import { computeSync, sha224, sha256, sha384, sha512, type Sha2 } from "../sha2/module.f.ts"
 import { all, concat, computeK, fromCurve, sign } from "./module.f.ts"
-import { assertEq } from '../../asserts/module.f.ts'
+import { assertEq } from '../../asserts/module.f.mjs'
 
 const sample = utf8("sample")
 const test = utf8("test")

diff --git a/fjs/crypto/vdf/proof.f.ts b/fjs/crypto/vdf/proof.f.ts
@@ -1,5 +1,5 @@
 import { sloth, p } from './module.f.ts'
-import { assert, assertEq } from '../../asserts/module.f.ts'
+import { assert, assertEq } from '../../asserts/module.f.mjs'
 
 const { eval: evalVdf, verify, modSqrt, quadRes } = sloth
 

diff --git a/fjs/dev/module.f.ts b/fjs/dev/module.f.ts
@@ -18,7 +18,7 @@ import type { StringMap } from '../types/object/module.f.ts'
 import { unwrap } from '../types/result/module.f.ts'
 import { pure, step, type Effect } from '../effects/module.f.ts'
 import { join, relativize, toPosix } from '../path/module.f.ts'
-import { assert, assertEq } from '../asserts/module.f.ts'
+import { assert, assertEq } from '../asserts/module.f.mjs'
 import { emptyState, virtual, type Dir } from '../effects/node/virtual/module.f.ts'
 
 export type Module = {

diff --git a/fjs/dev/package_json/proof.f.ts b/fjs/dev/package_json/proof.f.ts
@@ -1,4 +1,4 @@
-import { assert, assertEq } from '../../asserts/module.f.ts'
+import { assert, assertEq } from '../../asserts/module.f.mjs'
 import { unwrap } from '../../types/result/module.f.ts'
 import {
     validatePackageJson,

diff --git a/fjs/dev/proof.f.ts b/fjs/dev/proof.f.ts
@@ -1,4 +1,4 @@
-import { assert, assertEq, todo } from '../asserts/module.f.ts'
+import { assert, assertEq, todo } from '../asserts/module.f.mjs'
 import { shouldLoad } from './module.f.ts'
 
 export const proof = {

diff --git a/fjs/dev/update/proof.f.ts b/fjs/dev/update/proof.f.ts
@@ -3,7 +3,7 @@
  *
  * @module
  */
-import { assert, assertEq } from '../../asserts/module.f.ts'
+import { assert, assertEq } from '../../asserts/module.f.mjs'
 import { utf8 } from '../../text/module.f.ts'
 import { readUtf8File } from '../../effects/node/module.f.ts'
 import { defaultNodeProgramOptions, emptyState, virtual } from '../../effects/node/virtual/module.f.ts'

diff --git a/fjs/djs/ast/proof.f.ts b/fjs/djs/ast/proof.f.ts
@@ -1,7 +1,7 @@
 import { sort } from '../../types/object/module.f.ts'
 import { run } from './module.f.ts'
 import { stringifyAsTree } from '../serializer/module.f.ts'
-import { assertEq } from '../../asserts/module.f.ts'
+import { assertEq } from '../../asserts/module.f.mjs'
 
 export const proof = {
     test: () => {

diff --git a/fjs/djs/parser/module.f.ts b/fjs/djs/parser/module.f.ts
@@ -11,7 +11,7 @@ import { setReplace, at, type OrderedMap } from '../../types/ordered_map/module.
 import { fromMap } from '../../types/object/module.f.ts'
 import type { AstArray, AstConst, AstModule, AstModuleRef } from '../ast/module.f.ts'
 import type { TokenMetadata } from '../../js/tokenizer/module.f.ts'
-import { assertEq } from '../../asserts/module.f.ts'
+import { assertEq } from '../../asserts/module.f.mjs'
 
 export type ParseError = {
     readonly message: string,

diff --git a/fjs/djs/parser/proof.f.ts b/fjs/djs/parser/proof.f.ts
@@ -5,7 +5,7 @@ import { sort } from '../../types/object/module.f.ts'
 import { stringToList } from '../../text/utf16/module.f.ts'
 import { stringifyAsTree } from '../serializer/module.f.ts'
 import { stringify } from '../../media/json/module.f.ts'
-import { assert, assertEq } from '../../asserts/module.f.ts'
+import { assert, assertEq } from '../../asserts/module.f.mjs'
 
 const tokenizeString
     : (s: string) => readonly DjsTokenWithMetadata[]

diff --git a/fjs/djs/proof.f.ts b/fjs/djs/proof.f.ts
@@ -2,7 +2,7 @@ import { compile } from './module.f.ts'
 import { virtual, emptyState } from '../effects/node/virtual/module.f.ts'
 import { utf8, utf8ToString } from '../text/module.f.ts'
 import type { Vec } from '../types/bit_vec/module.f.ts'
-import { assert, assertEq } from '../asserts/module.f.ts'
+import { assert, assertEq } from '../asserts/module.f.mjs'
 
 const readOutput = (root: typeof emptyState.root, path: string): string => {
     const file = root[path]

diff --git a/fjs/djs/serializer/proof.f.ts b/fjs/djs/serializer/proof.f.ts
@@ -2,7 +2,7 @@ import { countRefs, stringify, stringifyAsTree } from './module.f.ts'
 import { sort } from '../../types/object/module.f.ts'
 import { identity } from '../../types/function/module.f.ts'
 import { setProperty } from '../../media/json/module.f.ts'
-import { assertEq } from '../../asserts/module.f.ts'
+import { assertEq } from '../../asserts/module.f.mjs'
 
 export const proof = {
     stringify: [

diff --git a/fjs/djs/tokenizer/proof.f.ts b/fjs/djs/tokenizer/proof.f.ts
@@ -2,7 +2,7 @@ import { descentParser } from '../../bnf/descent/module.f.ts'
 import { stringToCodePointList, stringToList } from '../../text/utf16/module.f.ts'
 import { toArray } from '../../types/list/module.f.ts'
 import { jsGrammar, tokenizeString, descentParserCpOnly, tokenizeJs, tokenize } from './module.f.ts'
-import { assert, assertEq } from '../../asserts/module.f.ts'
+import { assert, assertEq } from '../../asserts/module.f.mjs'
 import { stringifyAsTree } from '../serializer/module.f.ts'
 import { sort } from '../../types/object/module.f.ts'
 import type { Unknown } from '../module.f.ts'

diff --git a/fjs/djs/transpiler/proof.f.ts b/fjs/djs/transpiler/proof.f.ts
@@ -3,7 +3,7 @@ import { transpile } from './module.f.ts'
 import { stringifyAsTree } from '../serializer/module.f.ts'
 import { virtual, emptyState, type Dir } from '../../effects/node/virtual/module.f.ts'
 import { utf8 } from '../../text/module.f.ts'
-import { assert, assertEq } from '../../asserts/module.f.ts'
+import { assert, assertEq } from '../../asserts/module.f.mjs'
 
 const run = (root: Dir) => (path: string) => {
     const [_, result] = virtual({ ...emptyState, root })(transpile(path))

diff --git a/fjs/effects/eff/proof.f.ts b/fjs/effects/eff/proof.f.ts
@@ -1,5 +1,5 @@
 import { do_, match, pure } from '../module.f.ts'
-import { assert, assertEq } from '../../asserts/module.f.ts'
+import { assert, assertEq } from '../../asserts/module.f.mjs'
 import { assertPure } from '../proof.f.ts'
 import { eff } from './module.f.ts'
 

diff --git a/fjs/effects/memory/proof.f.ts b/fjs/effects/memory/proof.f.ts
@@ -1,4 +1,4 @@
-import { assert, assertEq } from '../../asserts/module.f.ts'
+import { assert, assertEq } from '../../asserts/module.f.mjs'
 import { run, type MemOperationMap } from '../mock/module.f.ts'
 import { pure, step } from '../module.f.ts'
 import {

diff --git a/fjs/effects/module.f.ts b/fjs/effects/module.f.ts
@@ -95,7 +95,7 @@
  * @module
  */
 
-import { assert } from '../asserts/module.f.ts'
+import { assert } from '../asserts/module.f.mjs'
 import { fold, type List } from '../types/list/module.f.ts'
 import { at } from '../types/object/module.f.ts'
 import type { Option } from '../types/option/module.f.ts'