Program:

export function test(): void {
  let foo = 0
  while (true) {
    foo++
    if (foo < 10) {
      3
    } else {
      break
    }
  }
  return
}

compiled with: asc test.ts -o test.wasm -O3 --runtime none
run with wasmtime results in

Error: failed to run main module `test.wasm`

Caused by:
    0: failed to invoke `test`
    1: wasm trap: unreachable, source location: @0049
       wasm backtrace:
         0: <unknown>!<wasm function 0>

I originally discovered this running on Node.js, but checked with wasmtime as well.

If the logic is reversed and the break is in the if clause, this works just fine.