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// run
// Copyright 2019 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// short-circuiting interface-to-concrete comparisons
// will not miss panics
package main
import (
"log"
"strings"
)
func main() {
var (
x interface{}
p *int
s []int
l *interface{}
r []*int
)
tests := []struct {
name string
errStr string
f func()
}{
{"switch case", "", func() {
switch x {
case x.(*int):
}
}},
{"interface conversion", "", func() { _ = x == x.(error) }},
{"type assertion", "", func() { _ = x == x.(*int) }},
{"out of bounds", "", func() { _ = x == s[1] }},
{"nil pointer dereference #1", "", func() { _ = x == *p }},
// TODO(mdempsky): Restore "nil pointer dereference" check. The Go
// spec doesn't mandate an order for panics (or even panic
// messages), but left-to-right is less confusing to users.
{"nil pointer dereference #2", "", func() { _ = *l == r[0] }},
{"nil pointer dereference #3", "", func() { _ = *l == any(r[0]) }},
}
for _, tc := range tests {
testFuncShouldPanic(tc.name, tc.errStr, tc.f)
}
}
func testFuncShouldPanic(name, want string, f func()) {
defer func() {
e := recover()
if e == nil {
log.Fatalf("%s: comparison did not panic\n", name)
}
if have := e.(error).Error(); !strings.Contains(have, want) {
log.Fatalf("%s: wrong panic message: have %q, want %q\n", name, have, want)
}
}()
f()
}
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