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package main
import (
"fmt"
"reflect"
"time"
)
type TestStruct struct{}
func (t TestStruct) String() string {
return "hello world"
}
type DummyStringer interface{
String() string
}
func main() {
aType := reflect.TypeOf((*fmt.Stringer)(nil)).Elem()
var t interface{}
t = time.Nanosecond
s, ok := t.(fmt.Stringer)
if !ok {
fmt.Println("time.Nanosecond does not implement fmt.Stringer")
return
}
fmt.Println(s.String())
fmt.Println(t.(fmt.Stringer).String())
bType := reflect.TypeOf(time.Nanosecond)
fmt.Println(bType.Implements(aType))
// not redundant with the above, because it goes through a slightly different code path.
if _, ok := t.(fmt.Stringer); !ok {
fmt.Println("time.Nanosecond does not implement fmt.Stringer")
return
} else {
fmt.Println("time.Nanosecond implements fmt.Stringer")
}
t = 42
foo, ok := t.(fmt.Stringer)
if !ok {
fmt.Println("42 does not implement fmt.Stringer")
} else {
fmt.Println("42 implements fmt.Stringer")
return
}
_ = foo
if _, ok := t.(fmt.Stringer); !ok {
fmt.Println("42 does not implement fmt.Stringer")
} else {
fmt.Println("42 implements fmt.Stringer")
return
}
// TODO(mpl): restore when fixed
// var tt interface{}
var tt DummyStringer
tt = TestStruct{}
ss, ok := tt.(fmt.Stringer)
if !ok {
fmt.Println("TestStuct does not implement fmt.Stringer")
return
}
fmt.Println(ss.String())
fmt.Println(tt.(fmt.Stringer).String())
if _, ok := tt.(fmt.Stringer); !ok {
fmt.Println("TestStuct does not implement fmt.Stringer")
return
} else {
fmt.Println("TestStuct implements fmt.Stringer")
}
}
// Output:
// 1ns
// 1ns
// true
// time.Nanosecond implements fmt.Stringer
// 42 does not implement fmt.Stringer
// 42 does not implement fmt.Stringer
// hello world
// hello world
// TestStuct implements fmt.Stringer
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