go method 源码

golang method 代码

文件路径：/test/method.go

// run

// 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.

// Test simple methods of various types, with pointer and
// value receivers.

package main

type S string
type S1 string
type I int
type I1 int
type T struct {
	x int
}
type T1 T

func (s S) val() int   { return 1 }
func (s *S1) val() int { return 2 }
func (i I) val() int   { return 3 }
func (i *I1) val() int { return 4 }
func (t T) val() int   { return 7 }
func (t *T1) val() int { return 8 }

type Val interface {
	val() int
}

func val(v Val) int { return v.val() }

func main() {
	var s S
	var ps *S1
	var i I
	var pi *I1
	var pt *T1
	var t T
	var v Val

	if s.val() != 1 {
		println("s.val:", s.val())
		panic("fail")
	}
	if S.val(s) != 1 {
		println("S.val(s):", S.val(s))
		panic("fail")
	}
	if (*S).val(&s) != 1 {
		println("(*S).val(s):", (*S).val(&s))
		panic("fail")
	}
	if ps.val() != 2 {
		println("ps.val:", ps.val())
		panic("fail")
	}
	if (*S1).val(ps) != 2 {
		println("(*S1).val(ps):", (*S1).val(ps))
		panic("fail")
	}
	if i.val() != 3 {
		println("i.val:", i.val())
		panic("fail")
	}
	if I.val(i) != 3 {
		println("I.val(i):", I.val(i))
		panic("fail")
	}
	if (*I).val(&i) != 3 {
		println("(*I).val(&i):", (*I).val(&i))
		panic("fail")
	}
	if pi.val() != 4 {
		println("pi.val:", pi.val())
		panic("fail")
	}
	if (*I1).val(pi) != 4 {
		println("(*I1).val(pi):", (*I1).val(pi))
		panic("fail")
	}
	if t.val() != 7 {
		println("t.val:", t.val())
		panic("fail")
	}
	if pt.val() != 8 {
		println("pt.val:", pt.val())
		panic("fail")
	}
	if (*T1).val(pt) != 8 {
		println("(*T1).val(pt):", (*T1).val(pt))
		panic("fail")
	}

	if val(s) != 1 {
		println("val(s):", val(s))
		panic("fail")
	}
	if val(ps) != 2 {
		println("val(ps):", val(ps))
		panic("fail")
	}
	if val(i) != 3 {
		println("val(i):", val(i))
		panic("fail")
	}
	if val(pi) != 4 {
		println("val(pi):", val(pi))
		panic("fail")
	}
	if val(t) != 7 {
		println("val(t):", val(t))
		panic("fail")
	}
	if val(pt) != 8 {
		println("val(pt):", val(pt))
		panic("fail")
	}

	if Val.val(i) != 3 {
		println("Val.val(i):", Val.val(i))
		panic("fail")
	}
	v = i
	if Val.val(v) != 3 {
		println("Val.val(v):", Val.val(v))
		panic("fail")
	}

	var zs struct{ S }
	var zps struct{ *S1 }
	var zi struct{ I }
	var zpi struct{ *I1 }
	var zpt struct{ *T1 }
	var zt struct{ T }
	var zv struct{ Val }

	if zs.val() != 1 {
		println("zs.val:", zs.val())
		panic("fail")
	}
	if zps.val() != 2 {
		println("zps.val:", zps.val())
		panic("fail")
	}
	if zi.val() != 3 {
		println("zi.val:", zi.val())
		panic("fail")
	}
	if zpi.val() != 4 {
		println("zpi.val:", zpi.val())
		panic("fail")
	}
	if zt.val() != 7 {
		println("zt.val:", zt.val())
		panic("fail")
	}
	if zpt.val() != 8 {
		println("zpt.val:", zpt.val())
		panic("fail")
	}

	if val(zs) != 1 {
		println("val(zs):", val(zs))
		panic("fail")
	}
	if val(zps) != 2 {
		println("val(zps):", val(zps))
		panic("fail")
	}
	if val(zi) != 3 {
		println("val(zi):", val(zi))
		panic("fail")
	}
	if val(zpi) != 4 {
		println("val(zpi):", val(zpi))
		panic("fail")
	}
	if val(zt) != 7 {
		println("val(zt):", val(zt))
		panic("fail")
	}
	if val(zpt) != 8 {
		println("val(zpt):", val(zpt))
		panic("fail")
	}

	zv.Val = zi
	if zv.val() != 3 {
		println("zv.val():", zv.val())
		panic("fail")
	}

	if (&zs).val() != 1 {
		println("(&zs).val:", (&zs).val())
		panic("fail")
	}
	if (&zps).val() != 2 {
		println("(&zps).val:", (&zps).val())
		panic("fail")
	}
	if (&zi).val() != 3 {
		println("(&zi).val:", (&zi).val())
		panic("fail")
	}
	if (&zpi).val() != 4 {
		println("(&zpi).val:", (&zpi).val())
		panic("fail")
	}
	if (&zt).val() != 7 {
		println("(&zt).val:", (&zt).val())
		panic("fail")
	}
	if (&zpt).val() != 8 {
		println("(&zpt).val:", (&zpt).val())
		panic("fail")
	}

	if val(&zs) != 1 {
		println("val(&zs):", val(&zs))
		panic("fail")
	}
	if val(&zps) != 2 {
		println("val(&zps):", val(&zps))
		panic("fail")
	}
	if val(&zi) != 3 {
		println("val(&zi):", val(&zi))
		panic("fail")
	}
	if val(&zpi) != 4 {
		println("val(&zpi):", val(&zpi))
		panic("fail")
	}
	if val(&zt) != 7 {
		println("val(&zt):", val(&zt))
		panic("fail")
	}
	if val(&zpt) != 8 {
		println("val(&zpt):", val(&zpt))
		panic("fail")
	}

	zv.Val = &zi
	if zv.val() != 3 {
		println("zv.val():", zv.val())
		panic("fail")
	}

	promotion()
}

type A struct{ B }
type B struct {
	C
	*D
}
type C int

func (C) f()  {} // value receiver, direct field of A
func (*C) g() {} // pointer receiver

type D int

func (D) h()  {} // value receiver, indirect field of A
func (*D) i() {} // pointer receiver

func expectPanic() {
	if r := recover(); r == nil {
		panic("expected nil dereference")
	}
}

func promotion() {
	var a A
	// Addressable value receiver.
	a.f()
	a.g()
	func() {
		defer expectPanic()
		a.h() // dynamic error: nil dereference in a.B.D->f()
	}()
	a.i()

	// Non-addressable value receiver.
	A(a).f()
	// A(a).g() // static error: cannot call pointer method on A literal.B.C
	func() {
		defer expectPanic()
		A(a).h() // dynamic error: nil dereference in A().B.D->f()
	}()
	A(a).i()

	// Pointer receiver.
	(&a).f()
	(&a).g()
	func() {
		defer expectPanic()
		(&a).h() // dynamic error: nil deref: nil dereference in (&a).B.D->f()
	}()
	(&a).i()

	c := new(C)
	c.f() // makes a copy
	c.g()
}

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