golang explicit 代码
文件路径：/test/interface/explicit.go
/ errorcheck
/ 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.
/ Verify compiler messages about erroneous static interface conversions.
/ Does not compile.
package main
type T struct {
a int
}
var t *T
type X int
func (x *X) M() {}
type I interface {
M()
}
var i I
type I2 interface {
M()
N()
}
var i2 I2
type E interface{}
var e E
func main() {
e = t / ok
t = e / ERROR "need explicit|need type assertion"
/ neither of these can work,
/ because i has an extra method
/ that t does not, so i cannot contain a t.
i = t / ERROR "incompatible|missing M method"
t = i / ERROR "incompatible|assignment$"
i = i2 / ok
i2 = i / ERROR "incompatible|missing N method"
i = I(i2) / ok
i2 = I2(i) / ERROR "invalid|missing N method|cannot convert"
e = E(t) / ok
t = T(e) / ERROR "need explicit|need type assertion|incompatible|cannot convert"
/ cannot type-assert non-interfaces
f := 2.0
_ = f.(int) / ERROR "non-interface type|only valid for interface types|not an interface"
}
type M interface {
M()
}
var m M
var _ = m.(int) / ERROR "impossible type assertion"
type Int int
func (Int) M(float64) {}
var _ = m.(Int) / ERROR "impossible type assertion"
var _ = m.(X) / ERROR "pointer receiver"
var ii int
var jj Int
var m1 M = ii / ERROR "incompatible|missing"
var m2 M = jj / ERROR "incompatible|wrong type for M method"
var m3 = M(ii) / ERROR "invalid|missing|cannot convert"
var m4 = M(jj) / ERROR "invalid|wrong type for M method|cannot convert"
type B1 interface {
_() / ERROR "methods must have a unique non-blank name"
}
type B2 interface {
M()
_() / ERROR "methods must have a unique non-blank name"
}
type T2 struct{}
func (t *T2) M() {}
func (t *T2) _() {}
/ Already reported about the invalid blank interface method above;
/ no need to report about not implementing it.
var b1 B1 = &T2{}
var b2 B2 = &T2{}