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// $G $D/$F.go && $L $F.$A && ./$A.out

// Copyright 2009 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.

// Check uses of all the different interface

// conversion runtime functions.

package main

type Stringer interface {

        String() string

}

type StringLengther interface {

        String() string

        Length() int

}

type Empty interface{}

type T string

func (t T) String() string {

        return string(t)

}

func (t T) Length() int {

        return len(t)

}

type U string

func (u U) String() string {

        return string(u)

}

var t = T("hello")

var u = U("goodbye")

var e Empty

var s Stringer = t

var sl StringLengther = t

var i int

var ok bool

func hello(s string) {

        if s != "hello" {

                println("not hello: ", s)

                panic("fail")

        }

}

func five(i int) {

        if i != 5 {

                println("not 5: ", i)

                panic("fail")

        }

}

func true(ok bool) {

        if !ok {

                panic("not true")

        }

}

func false(ok bool) {

        if ok {

                panic("not false")

        }

}

func main() {

        // T2I

        s = t

        hello(s.String())

        // I2T

        t = s.(T)

        hello(t.String())

        // T2E

        e = t

        // E2T

        t = e.(T)

        hello(t.String())

        // T2I again

        sl = t

        hello(sl.String())

        five(sl.Length())

        // I2I static

        s = sl

        hello(s.String())

        // I2I dynamic

        sl = s.(StringLengther)

        hello(sl.String())

        five(sl.Length())

        // I2E (and E2T)

        e = s

        hello(e.(T).String())

        // E2I

        s = e.(Stringer)

        hello(s.String())

        // I2T2 true

        t, ok = s.(T)

        true(ok)

        hello(t.String())

        // I2T2 false

        _, ok = s.(U)

        false(ok)

        // I2I2 true

        sl, ok = s.(StringLengther)

        true(ok)

        hello(sl.String())

        five(sl.Length())

        // I2I2 false (and T2I)

        s = u

        sl, ok = s.(StringLengther)

        false(ok)

        // E2T2 true

        t, ok = e.(T)

        true(ok)

        hello(t.String())

        // E2T2 false

        i, ok = e.(int)

        false(ok)

        // E2I2 true

        sl, ok = e.(StringLengther)

        true(ok)

        hello(sl.String())

        five(sl.Length())

        // E2I2 false (and T2E)

        e = u

        sl, ok = e.(StringLengther)

        false(ok)

}