实例化合约时报错

[missop]

   public async getFungibleToken(): Promise<FungibleToken> {
        const _fungibleToken = await Provable.witnessAsync(PublicKey, async () => {
            let pk = await this.fungibleToken.fetch()
            assert(pk !== undefined, "fungible token not found")
            return pk
        });
        this.fungibleToken.requireEquals(_fungibleToken);
        return (new Crowdfunding.FungibleTokenContract(_fungibleToken));
    }

x.toConstant() was called on a variable field element x in provable code.
This is not supported, because variables represent an abstract computation,
which only carries actual values during proving, but not during compiling.

Also, reading out JS values means that whatever you're doing with those values will no longer be
linked to the original variable in the proof, which makes this pattern prone to security holes.

You can check whether your field element is a variable or a constant by using x.isConstant().

To inspect values for debugging, use Provable.log(x). For more advanced use cases,
there is `Provable.asProver(() => { ... })` which allows you to use x.toConstant() inside the callback.
Warning: whatever happens inside asProver() will not be part of the zk proof.

  37 |     public async getFungibleToken(): Promise<FungibleToken> {
  38 |         const _fungibleToken = await Provable.witnessAsync(PublicKey, async () => {
> 39 |             let pk = await this.fungibleToken.fetch()
     |                                               ^
  40 |             assert(pk !== undefined, "fungible token not found")
  41 |             return pk
  42 |         });