package main

import (
	"fmt"
	"github.com/go-test/deep"
)

type foo struct {
	bar error
}

func main() {
	deep.CompareUnexportedFields = true
	e1 := foo{bar: fmt.Errorf("error")}
	e2 := foo{bar: fmt.Errorf("error")}
	deep.Equal(e1, e2)
}

$ go run deep_panic.go
panic: reflect: reflect.flag.mustBeExported using value obtained using unexported field

goroutine 1 [running]:
reflect.flag.mustBeExportedSlow(0x2b3)
	/usr/local/Cellar/go/1.14.3/libexec/src/reflect/value.go:225 +0x12e
reflect.flag.mustBeExported(...)
	/usr/local/Cellar/go/1.14.3/libexec/src/reflect/value.go:216
reflect.Value.Call(0x10e1ca0, 0xc00008e230, 0x2b3, 0x0, 0x0, 0x0, 0xc00008e230, 0x2b3, 0x0)
	/usr/local/Cellar/go/1.14.3/libexec/src/reflect/value.go:320 +0x4d
github.com/go-test/deep.(*cmp).equals(0xc00009aeb0, 0x10e1ca0, 0xc00008e230, 0xb4, 0x10e1ca0, 0xc00008e240, 0xb4, 0x1)
	/Users/seveas/go/pkg/mod/github.com/go-test/deep@v1.0.7/deep.go:145 +0x335b
github.com/go-test/deep.(*cmp).equals(0xc00009aeb0, 0x10e3040, 0xc00008e230, 0x99, 0x10e3040, 0xc00008e240, 0x99, 0x0)
	/Users/seveas/go/pkg/mod/github.com/go-test/deep@v1.0.7/deep.go:223 +0x246c
github.com/go-test/deep.Equal(0x10e3040, 0xc00008e230, 0x10e3040, 0xc00008e240, 0x0, 0x11203e0, 0xc00008e220)
	/Users/seveas/go/pkg/mod/github.com/go-test/deep@v1.0.7/deep.go:88 +0x2b4
main.main()
	/Users/seveas/code/katyusha/deep_panic.go:16 +0x118
exit status 2