issue62203.go

     1  // run
     2  
     3  // Copyright 2023 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  	"maps"
    12  )
    13  
    14  func main() {
    15  	m := map[string]struct{}{}
    16  
    17  	// Fill m up to the max for 4 buckets = 48 entries.
    18  	for i := 0; i < 48; i++ {
    19  		m[fmt.Sprintf("%d", i)] = struct{}{}
    20  	}
    21  
    22  	// Add a 49th entry, to start a grow to 8 buckets.
    23  	m["foo"] = struct{}{}
    24  
    25  	// Remove that 49th entry. m is still growing to 8 buckets,
    26  	// but a clone of m will only have 4 buckets because it
    27  	// only needs to fit 48 entries.
    28  	delete(m, "foo")
    29  
    30  	// Clone an 8-bucket map to a 4-bucket map.
    31  	_ = maps.Clone(m)
    32  }
    33
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