Is there a problem with iface's nil judgment?

[ztorchan]

tencentcloud-sdk-go/tencentcloud/sts/v20180813/client.go

Lines 182 to 184 in 60b9839

	if c.GetCredential() == nil {
	return nil, errors.New("AssumeRole require credential")
	}

tencentcloud-sdk-go/tencentcloud/common/client.go

Lines 546 to 548 in 60b9839

	func (c *Client) GetCredential() CredentialIface {
	return c.credential
	}

tencentcloud-sdk-go/tencentcloud/common/credentials.go

Lines 5 to 12 in 60b9839

	type CredentialIface interface {
	GetSecretId() string
	GetToken() string
	GetSecretKey() string
	GetCredential() (string, string, string)
	// needRefresh() bool
	// refresh()
	}

GetCredential() return a iface. Even if its value is nil, no error will be reported here when its type is not nil, which will cause panic in the following process.

[sesky4]

hi ztorchan, can you elaborate more on when its type is not nil ? im not sure what that means.

[sesky4]

oh, I see.

a interface will not be equal to nil even the value it contains is nil.
the following example will output

true true
false true
false false

package main

import (
	"io"
)

type Fake struct {
}

func (f *Fake) Write(b []byte) (int, error) {
	return 0, nil
}

func main() {
	var a io.Writer
	var b *Fake
	println(a == nil, b == nil)
	a = b
	println(a == nil, b == nil)
	b = &Fake{}
	println(a == nil, b == nil)
}

But i think its fine, since it will panic and show you the error stack.