go explicit 源码
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{}
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