ifaceconv.go

     1  // run
     2  
     3  // Copyright 2021 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  // Test that we can convert type parameters to both empty
     8  // and nonempty interfaces, and named and nonnamed versions
     9  // thereof.
    10  
    11  package main
    12  
    13  import "fmt"
    14  
    15  type E interface{}
    16  
    17  func f[T any](x T) interface{} {
    18  	var i interface{} = x
    19  	return i
    20  }
    21  
    22  func fs[T any](x T) interface{} {
    23  	y := []T{x}
    24  	var i interface{} = y
    25  	return i
    26  }
    27  
    28  func g[T any](x T) E {
    29  	var i E = x
    30  	return i
    31  }
    32  
    33  type C interface {
    34  	foo() int
    35  }
    36  
    37  type myInt int
    38  
    39  func (x myInt) foo() int {
    40  	return int(x + 1)
    41  }
    42  
    43  func h[T C](x T) interface{ foo() int } {
    44  	var i interface{ foo() int } = x
    45  	return i
    46  }
    47  func i[T C](x T) C {
    48  	var i C = x // conversion in assignment
    49  	return i
    50  }
    51  
    52  func j[T C](t T) C {
    53  	return C(t) // explicit conversion
    54  }
    55  
    56  func js[T any](x T) interface{} {
    57  	y := []T{x}
    58  	return interface{}(y)
    59  }
    60  
    61  func main() {
    62  	if got, want := f[int](7), 7; got != want {
    63  		panic(fmt.Sprintf("got %d want %d", got, want))
    64  	}
    65  	if got, want := fs[int](7), []int{7}; got.([]int)[0] != want[0] {
    66  		panic(fmt.Sprintf("got %d want %d", got, want))
    67  	}
    68  	if got, want := g[int](7), 7; got != want {
    69  		panic(fmt.Sprintf("got %d want %d", got, want))
    70  	}
    71  	if got, want := h[myInt](7).foo(), 8; got != want {
    72  		panic(fmt.Sprintf("got %d want %d", got, want))
    73  	}
    74  	if got, want := i[myInt](7).foo(), 8; got != want {
    75  		panic(fmt.Sprintf("got %d want %d", got, want))
    76  	}
    77  	if got, want := j[myInt](7).foo(), 8; got != want {
    78  		panic(fmt.Sprintf("got %d want %d", got, want))
    79  	}
    80  	if got, want := js[int](7), []int{7}; got.([]int)[0] != want[0] {
    81  		panic(fmt.Sprintf("got %d want %d", got, want))
    82  	}
    83  }
    84
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