ifaceconv.go

Documentation: golang.org/x/tools/go/ssa/interp/testdata

     1  package main
     2  
     3  // Tests of interface conversions and type assertions.
     4  
     5  type I0 interface {
     6  }
     7  type I1 interface {
     8  	f()
     9  }
    10  type I2 interface {
    11  	f()
    12  	g()
    13  }
    14  
    15  type C0 struct{}
    16  type C1 struct{}
    17  
    18  func (C1) f() {}
    19  
    20  type C2 struct{}
    21  
    22  func (C2) f() {}
    23  func (C2) g() {}
    24  
    25  func main() {
    26  	var i0 I0
    27  	var i1 I1
    28  	var i2 I2
    29  
    30  	// Nil always causes a type assertion to fail, even to the
    31  	// same type.
    32  	if _, ok := i0.(I0); ok {
    33  		panic("nil i0.(I0) succeeded")
    34  	}
    35  	if _, ok := i1.(I1); ok {
    36  		panic("nil i1.(I1) succeeded")
    37  	}
    38  	if _, ok := i2.(I2); ok {
    39  		panic("nil i2.(I2) succeeded")
    40  	}
    41  
    42  	// Conversions can't fail, even with nil.
    43  	_ = I0(i0)
    44  
    45  	_ = I0(i1)
    46  	_ = I1(i1)
    47  
    48  	_ = I0(i2)
    49  	_ = I1(i2)
    50  	_ = I2(i2)
    51  
    52  	// Non-nil type assertions pass or fail based on the concrete type.
    53  	i1 = C1{}
    54  	if _, ok := i1.(I0); !ok {
    55  		panic("C1 i1.(I0) failed")
    56  	}
    57  	if _, ok := i1.(I1); !ok {
    58  		panic("C1 i1.(I1) failed")
    59  	}
    60  	if _, ok := i1.(I2); ok {
    61  		panic("C1 i1.(I2) succeeded")
    62  	}
    63  
    64  	i1 = C2{}
    65  	if _, ok := i1.(I0); !ok {
    66  		panic("C2 i1.(I0) failed")
    67  	}
    68  	if _, ok := i1.(I1); !ok {
    69  		panic("C2 i1.(I1) failed")
    70  	}
    71  	if _, ok := i1.(I2); !ok {
    72  		panic("C2 i1.(I2) failed")
    73  	}
    74  
    75  	// Conversions can't fail.
    76  	i1 = C1{}
    77  	if I0(i1) == nil {
    78  		panic("C1 I0(i1) was nil")
    79  	}
    80  	if I1(i1) == nil {
    81  		panic("C1 I1(i1) was nil")
    82  	}
    83  }
    84
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