Wrong print msg when comparing initialized and uninitialized slice

[samlaf]

Actual behavior A clear and concise description of what the bug is.

=== RUN   TestA
    tests/A_test.go:15: Unexpected call to *tests.MockAer.Hello([[]]) at tests/A_test.go:15 because:
        expected call at tests/A_test.go:14 doesn't match the argument at index 0.
        Got: [] ([][32]uint8)
        Want: is equal to [] ([][32]uint8)

Expected behavior

=== RUN   TestA
    tests/A_test.go:15: Unexpected call to *tests.MockAer.Hello([[]]) at tests/A_test.go:15 because:
        expected call at tests/A_test.go:14 doesn't match the argument at index 0.
        Got: nil ([][32]uint8)
        Want: is equal to [] ([][32]uint8)

To Reproduce Steps to reproduce the behavior

Generate mocks for this interface

type Aer interface {
	Hello([][32]byte)
}

Then write this test

func TestA(t *testing.T) {
	ctrl := gomock.NewController(t)
	mockA := NewMockAer(ctrl)
	mockA.EXPECT().Hello([][32]byte{})
	mockA.Hello(nil)
}

You will reproduce the above error, which is very confusing. It's showing that Got and Want are the same, even though they actually aren't.

Additional Information

• gomock mode (reflect or source): not sure what this means.
• gomock version or git ref: go.uber.org/mock v0.2.0
• golang version: go version go1.20.6 darwin/arm64

[deansg]

Just wanted to mention that a similar issue was opened and not fixed in the archived golang/mock repo:
golang/mock#267
(it was merged into a different issue, whose solution didn't solve the original issue)