Incorrect schema generation for `NonNullable` of union type

[loucadufault]

Seems like a very simple repro:

Simpler repro:

export type SomeType = {
  foo: NonNullable<'a' | 'b'>
}

{
  "$ref": "#/definitions/RelaxedMatchedHeadline",
  "$schema": "http://json-schema.org/draft-07/schema#",
  "definitions": {
    "RelaxedMatchedHeadline": {
      "properties": {
        "foo": {
          "anyOf": [
            {
              "properties": {},
              "type": "object"
            },
            {
              "properties": {},
              "type": "object"
            }
          ]
        }
      },
      "type": "object"
    }
  }
}

on @2.4.0

[loucadufault]

Another weird example:

type A = {
  foo: 'a' | 'b'
}
export type SomeType = {
  foo: (Partial<A> & A)['foo']
}

{
  "$ref": "#/definitions/SomeType",
  "$schema": "http://json-schema.org/draft-07/schema#",
  "definitions": {
    "SomeType": {
      "additionalProperties": false,
      "properties": {
        "foo": {
          "anyOf": [
            {
              "const": "a",
              "type": "string"
            },
            {
              "properties": {},
              "type": "object"
            },
            {
              "properties": {},
              "type": "object"
            },
            {
              "const": "b",
              "type": "string"
            }
          ]
        }
      },
      "type": "object"
    }
  }
}

[domoritz]

NonNullable internally uses T & {} which I guess we don't handle well. Pull request welcome.

[loucadufault]

any hints on where to start looking @domoritz? Pretty unfamiliar with ts introspection but happy to take a stab at it

[domoritz]

Step through (instructions in the repo) the parsers with a debugger to see what it constructs and at which points it's wrong. If the parsing looks fine, step through at the formatters.