issue81299.go

     1  // run
     2  
     3  // Copyright 2026 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  package main
     8  
     9  import (
    10  	"fmt"
    11  	"hash/maphash"
    12  )
    13  
    14  func main() {
    15  	testEmpty()
    16  	testNonEmpty()
    17  }
    18  
    19  func testEmpty() {
    20  	s := maphash.MakeSeed()
    21  	hashes := map[uint64]struct{}{}
    22  	addHash := func(x any) {
    23  		var h maphash.Hash
    24  		h.SetSeed(s)
    25  		var c maphash.ComparableHasher[any]
    26  		c.Hash(&h, x)
    27  		hashes[h.Sum64()] = struct{}{}
    28  	}
    29  	addHash(int64(0))
    30  	addHash(uint64(0))
    31  	addHash(int(0))
    32  	addHash(uint(0))
    33  	if len(hashes) < 3 {
    34  		panic(fmt.Sprintf("too few hashes %v\n", hashes))
    35  	}
    36  }
    37  
    38  type I interface {
    39  	foo()
    40  }
    41  
    42  type I1 int64
    43  type I2 uint64
    44  type I3 int
    45  type I4 uint
    46  
    47  func (i I1) foo() {}
    48  func (i I2) foo() {}
    49  func (i I3) foo() {}
    50  func (i I4) foo() {}
    51  
    52  func testNonEmpty() {
    53  	s := maphash.MakeSeed()
    54  	hashes := map[uint64]struct{}{}
    55  	addHash := func(x I) {
    56  		var h maphash.Hash
    57  		h.SetSeed(s)
    58  		var c maphash.ComparableHasher[I]
    59  		c.Hash(&h, x)
    60  		hashes[h.Sum64()] = struct{}{}
    61  	}
    62  	addHash(I1(0))
    63  	addHash(I2(0))
    64  	addHash(I3(0))
    65  	addHash(I4(0))
    66  	if len(hashes) < 3 {
    67  		panic(fmt.Sprintf("too few hashes %v\n", hashes))
    68  	}
    69  }
    70
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