0.20.0-beta.24: constraint type parameters results in an error

[runarberg]

Search terms

• template constraints
• type parameter extends
• generic constraints

Expected Behavior

Docs should be generated without errors

Actual Behavior

Docs are not generated with the following error:

Error output

TypeDoc exiting with unexpected error:
AssertionError [ERR_ASSERTION]: The expression evaluated to a falsy value:

  assert(params.length === 1)

    at Object.convertType (/home/user/src/andcetera/node_modules/typedoc/dist/lib/converter/types.js:96:9)
    at Object.convertType (/home/user/src/andcetera/node_modules/typedoc/dist/lib/converter/types.js:80:34)
    at Converter.convertType (/home/user/src/andcetera/node_modules/typedoc/dist/lib/converter/converter.js:55:24)
    at /home/user/src/andcetera/node_modules/typedoc/dist/lib/converter/factories/signature.js:47:33
    at Array.map (<anonymous>)
    at convertTypeParameters (/home/user/src/andcetera/node_modules/typedoc/dist/lib/converter/factories/signature.js:43:79)
    at Object.createSignature (/home/user/src/andcetera/node_modules/typedoc/dist/lib/converter/factories/signature.js:20:29)
    at Object.convertFunctionOrMethod (/home/user/src/andcetera/node_modules/typedoc/dist/lib/converter/symbols.js:158:39)
    at Object.convertSymbol (/home/user/src/andcetera/node_modules/typedoc/dist/lib/converter/symbols.js:75:79)
    at Converter.convertExports (/home/user/src/andcetera/node_modules/typedoc/dist/lib/converter/converter.js:157:23) {
  generatedMessage: true,
  code: 'ERR_ASSERTION',
  actual: false,
  expected: true,
  operator: '=='
}

Steps to reproduce the bug

Note: I’m using TypeScript in JavaScript, but the bug is also reproducible in TypeScript (i.e. function foo<T extends unknown[]>()):

Write a function that uses a constraint generic type parameter (i.e. @template {Constraint} T):

src/combinators/zip.js

/**
 * Take any number of iterators, and zip them together into one iterator of
 * tuples. Closes after the shortest of the inputs closes.
 *
 * @template {unknown[]} A Tuple type with item type of each input iterator
 * @param {{ [K in keyof A]: Iterable<A[K]> }} items The iterators to be zipped
 * @returns {Iterable<A>}
 */
export default function* zip(...items) {
  const iters = items.map((item) => item[Symbol.iterator]());
  let buffer = iters.map((iter) => iter.next());

  while (!buffer.some(({ done }) => done)) {
    yield /** @type {A} */ (buffer.map(({ value }) => value));

    buffer = iters.map((iter) => iter.next());
  }
}

Try to generate the docs:

npx typecheck src/combinators/zip.js

See the error above.

tsconfig.json

{
  "compilerOptions": {
    "module": "ESNext",
    "target": "ESNext",
    "moduleResolution": "node",
    "allowSyntheticDefaultImports": true,
    "allowJs": true,
    "checkJs": true,
    "strict": true,
    "noEmit": true
  },
  "include": ["src/**/*.js"],
  "typedocOptions": {
    "mode": "library",
    "inputFiles": ["src/index.js"],
    "entryPoint": "index",
    "out": "docs"
  }
}

Environment

• Typedoc version: 0.20.0-beta.24
• TypeScript version: 4.1.2
• Node.js version: v15.1.0
• OS: Linux Ubuntu 20.10

[runarberg]

Possible related to #202

[Gerrit0]

This is.... really weird. The assert seems reasonable to me, and most of the time it works properly. The only time it doesn't appears to be when the array is in a constraint of a type parameter. Fixed in beta 25, and I've reached out of to some of the compiler team to see if they can enlighten me as to why an array has more than one type argument...