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      1 // errorcheck
      2 
      3 // Copyright 2009 The Go Authors. All rights reserved.
      4 // Use of this source code is governed by a BSD-style
      5 // license that can be found in the LICENSE file.
      6 
      7 // Verify compiler messages about erroneous static interface conversions.
      8 // Does not compile.
      9 
     10 package main
     11 
     12 type T struct {
     13 	a int
     14 }
     15 
     16 var t *T
     17 
     18 type X int
     19 
     20 func (x *X) M() {}
     21 
     22 type I interface {
     23 	M()
     24 }
     25 
     26 var i I
     27 
     28 type I2 interface {
     29 	M()
     30 	N()
     31 }
     32 
     33 var i2 I2
     34 
     35 type E interface{}
     36 
     37 var e E
     38 
     39 func main() {
     40 	e = t // ok
     41 	t = e // ERROR "need explicit|need type assertion"
     42 
     43 	// neither of these can work,
     44 	// because i has an extra method
     45 	// that t does not, so i cannot contain a t.
     46 	i = t // ERROR "incompatible|missing M method"
     47 	t = i // ERROR "incompatible|assignment$"
     48 
     49 	i = i2 // ok
     50 	i2 = i // ERROR "incompatible|missing N method"
     51 
     52 	i = I(i2)  // ok
     53 	i2 = I2(i) // ERROR "invalid|missing N method"
     54 
     55 	e = E(t) // ok
     56 	t = T(e) // ERROR "need explicit|need type assertion|incompatible"
     57 
     58 	// cannot type-assert non-interfaces
     59 	f := 2.0
     60 	_ = f.(int) // ERROR "non-interface type"
     61 
     62 }
     63 
     64 type M interface {
     65 	M()
     66 }
     67 
     68 var m M
     69 
     70 var _ = m.(int) // ERROR "impossible type assertion"
     71 
     72 type Int int
     73 
     74 func (Int) M(float64) {}
     75 
     76 var _ = m.(Int) // ERROR "impossible type assertion"
     77 
     78 var _ = m.(X) // ERROR "pointer receiver"
     79 
     80 var ii int
     81 var jj Int
     82 
     83 var m1 M = ii // ERROR "incompatible|missing"
     84 var m2 M = jj // ERROR "incompatible|wrong type for M method"
     85 
     86 var m3 = M(ii) // ERROR "invalid|missing"
     87 var m4 = M(jj) // ERROR "invalid|wrong type for M method"
     88 
     89 type B1 interface {
     90 	_() // ERROR "methods must have a unique non-blank name"
     91 }
     92 
     93 type B2 interface {
     94 	M()
     95 	_() // ERROR "methods must have a unique non-blank name"
     96 }
     97 
     98 type T2 struct{}
     99 
    100 func (t *T2) M() {}
    101 func (t *T2) _() {}
    102 
    103 // Check that nothing satisfies an interface with blank methods.
    104 var b1 B1 = &T2{} // ERROR "incompatible|missing _ method"
    105 var b2 B2 = &T2{} // ERROR "incompatible|missing _ method"
    106