Assert ErrorIs(): failure message shows identical strings when errors differ only by memory address.

[tscales]

context

the Assert.ErrorIs() method seems to expect that if the errors are not equal that the error chain will differ. This however is not the case when the errors are identical but differ in memory address.

current result

Error:      	Target error should be in err chain:
                 expected: "ERROR"
        	 in chain: "ERROR"
Test:       	TestAssertIs

expected result

the scenario described should still fail, but since the chains are identical, It might be helpful to have a different message.

files affected

https://github.com/stretchr/testify/blob/v1.8.1/assert/assertions.go#L1794-L1813

reproduce

type A struct {
	Value bool
}

func (a *A) Error() string {
	return "ERROR"
}

var aErr = A{}

func returnErr() error {
	return &aErr
}
func TestAssertIs(t *testing.T) {
	err := returnErr()
	target := A{}
	assert.ErrorIs(t, err, &target)
}