Union types of 3 types fail silently

[mimi89999]

Bug description

When using union types of 3 types, asbuild does not report any errors, but the functions are not exported

Steps to reproduce

1. Define a function accepting a parameter with a union type of 2 types. Notice that asc fails with an error:

ERROR AS100: Not implemented: union types
   :
 5 │ export function bar(a: i32 | u32): i32 {
   │                              ~~~
   └─ in assembly/index.ts(5,30)

2. Now use a union type of 3 types like in the following code:

export function foo(a: aaa | bbb | ccc): i32 {
  return 1;
}

export function bar(a: i32 | u32 | f32): i32 {
  return 1;
}

3. Run npm run asbuild
4. Notice that the build succeeds, but the functions are not present in the wasm file. When compiling the code I pasted, I got an empty .wat file and a minimal .wasm file:

$ xxd build/release.wasm
00000000: 0061 736d 0100 0000 0503 0100 0007 0a01  .asm............
00000010: 066d 656d 6f72 7902 0000 2410 736f 7572  .memory...$.sour
00000020: 6365 4d61 7070 696e 6755 524c 122e 2f72  ceMappingURL../r
00000030: 656c 6561 7365 2e77 6173 6d2e 6d61 70    elease.wasm.map

AssemblyScript version

0.27.29