Error: Invalid index "length" in type "[]"

[EladBezalel]

Bug: Invalid index "length" in type "[]"

Description

When running ts-json-schema-generator on a file containing the following TypeScript type:

export type Test = []['length'];

the tool throws an error:

Invalid index "length" in type "[]"

Steps to Reproduce

1. Create a file with this content:

   export type Test = []['length'];

2. Run:

   npx ts-json-schema-generator --path file.ts --type Test
   

Real-World Usage Example

We encountered this issue while using the IntRange type from the type-fest package.
IntRange relies on tuple length indexing as part of its type-level computation. For example:

import { IntRange } from 'type-fest';

type Range = IntRange<0, 10>; // 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9

Internally, IntRange and similar utilities use expressions like []['length'] to compute numeric ranges.
This means the inability to handle such indexed access types prevents us from generating JSON schemas for types that depend on IntRange and similar utilities.

[arthurfiorette]

Hey @EladBezalel, would you like to work on a PR to fix this?

[EladBezalel]

@arthurfiorette no problem as long as you direct me to what kind of fix you were looking for?