Rust中Vec的内存布局是什么？

Question

我有一个看起来像这样的枚举：

    package com.airobotfyp.livecricket;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

import com.google.android.gms.ads.AdListener;
import com.google.android.gms.ads.AdRequest;
import com.google.android.gms.ads.AdSize;
import com.google.android.gms.ads.AdView;
import com.google.android.gms.ads.InterstitialAd;
import com.google.android.gms.ads.MobileAds;


public class SplashScreen extends AppCompatActivity {
    private InterstitialAd mInterstitialAd;
    private AdView mAdView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_splash_screen);
        Button btnclk1 = (Button) findViewById(R.id.startbtn);
        Button btnclk2 = (Button) findViewById(R.id.startbtn2);

        MobileAds.initialize(this, "ca-app-pub-8972808858904277~8136901702");

        mAdView = findViewById(R.id.adView);
        AdRequest adRequest = new AdRequest.Builder().build();
        mAdView.loadAd(adRequest);
        AdView adView = new AdView(this);
        adView.setAdSize(AdSize.BANNER);
        adView.setAdUnitId("ca-app-pub-8972808858904277/7753758329");
        mAdView.setAdListener(new AdListener() {
            @Override
            public void onAdLoaded() {
                // Code to be executed when an ad finishes loading.
            }

            @Override
            public void onAdFailedToLoad(int errorCode) {
                // Code to be executed when an ad request fails.
            }

            @Override
            public void onAdOpened() {
                // Code to be executed when an ad opens an overlay that
                // covers the screen.
            }

            @Override
            public void onAdLeftApplication() {
                // Code to be executed when the user has left the app.
            }

            @Override
            public void onAdClosed() {
                // Code to be executed when the user is about to return
                // to the app after tapping on an ad.
            }
        });
        //full
        mInterstitialAd = new InterstitialAd(this);
        mInterstitialAd.setAdUnitId("ca-app-pub-8972808858904277/3431369930");
        mInterstitialAd.loadAd(new AdRequest.Builder().build());
        mInterstitialAd.setAdListener(new AdListener() {
            @Override
            public void onAdClosed() {
                // Load the next interstitial.
                mInterstitialAd.loadAd(new AdRequest.Builder().build());
            }
        });
        mInterstitialAd.setAdListener(new AdListener() {
            @Override
            public void onAdLoaded() {
                // Code to be executed when an ad finishes loading.
            }

            @Override
            public void onAdFailedToLoad(int errorCode) {
                // Code to be executed when an ad request fails.
            }

            @Override
            public void onAdOpened() {
                // Code to be executed when the ad is displayed.
            }

            @Override
            public void onAdLeftApplication() {
                // Code to be executed when the user has left the app.
            }

            @Override
            public void onAdClosed() {
                // Code to be executed when when the interstitial ad is closed.
            }
        });

        btnclk1.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                if (mInterstitialAd.isLoaded()) {
                    mInterstitialAd.show();
                } else {
                    Log.d("TAG", "The interstitial wasn't loaded yet.");
                }
                Intent mainIntent = new Intent(SplashScreen.this,Menu.class);
                startActivity(mainIntent);
            }
        });
        btnclk2.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                if (mInterstitialAd.isLoaded()) {
                    mInterstitialAd.show();
                } else {
                    Log.d("TAG", "The interstitial wasn't loaded yet.");
                }
            }
        });

    }
}

它正在用于为我正在教自己的Rust编写的一个简单解释器实现可变的整数存储（在Vec中），但是我在推理需要引用什么时遇到问题。

Vec在内存中的实际布局是什么样的？