issue60933.go

     1  // Copyright 2023 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package p
     6  
     7  import (
     8  	"io"
     9  	"os"
    10  )
    11  
    12  func g[T any](...T) {}
    13  
    14  // Interface and non-interface types do not match.
    15  func _() {
    16  	var file *os.File
    17  	g(file, io /* ERROR "type io.Writer of io.Discard does not match inferred type *os.File for T" */ .Discard)
    18  	g(file, os.Stdout)
    19  }
    20  
    21  func _() {
    22  	var a *os.File
    23  	var b any
    24  	g(a, a)
    25  	g(a, b /* ERROR "type any of b does not match inferred type *os.File for T" */)
    26  }
    27  
    28  var writer interface {
    29  	Write(p []byte) (n int, err error)
    30  }
    31  
    32  func _() {
    33  	var file *os.File
    34  	g(file, writer /* ERROR "type interface{Write(p []byte) (n int, err error)} of writer does not match inferred type *os.File for T" */)
    35  	g(writer, file /* ERROR "type *os.File of file does not match inferred type interface{Write(p []byte) (n int, err error)} for T" */)
    36  }
    37  
    38  // Different named interface types do not match.
    39  func _() {
    40  	g(io.ReadWriter(nil), io.ReadWriter(nil))
    41  	g(io.ReadWriter(nil), io /* ERROR "does not match" */ .Writer(nil))
    42  	g(io.Writer(nil), io /* ERROR "does not match" */ .ReadWriter(nil))
    43  }
    44  
    45  // Named and unnamed interface types match if they have the same methods.
    46  func _() {
    47  	g(io.Writer(nil), writer)
    48  	g(io.ReadWriter(nil), writer /* ERROR "does not match" */ )
    49  }
    50  
    51  // There must be no order dependency for named and unnamed interfaces.
    52  func f[T interface{ m(T) }](a, b T) {}
    53  
    54  type F interface {
    55  	m(F)
    56  }
    57  
    58  func _() {
    59  	var i F
    60  	var j interface {
    61  		m(F)
    62  	}
    63  
    64  	// order doesn't matter
    65  	f(i, j)
    66  	f(j, i)
    67  }
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