@massaExport transformer fails when used with more than one function that are using custom_type

[bilboquet]

I created an SC with the generator.
I added

import { u128, u256 } from "as-bignum/assembly";

// @ts-ignore: decorator
@massaExport()
export function test1(arg: u128) : u128 {
  return arg;
}

build, it worked
then I added a second function

// @ts-ignore: decorator
@massaExport()
export function test2(arg: u256) : u256 {
  return arg;
}

The build fails with (most relevant part of the trace):

MassaExport Function: generated 'test1' function's wrapper
contract to compile assembly/contracts/main.ts
Compilation failed: Cannot read properties of undefined (reading '0')
stderr FAILURE TypeError: Cannot read properties of undefined (reading '0')
    at file:///home/jf/workspace/assemblyscript/as/packages/as-transformer/dist/transformers/massaExport.js:42:94