issue50755.go

     1  // Copyright 2022 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  // The core type of M2 unifies with the type of m1
     8  // during function argument type inference.
     9  // M2's constraint is unnamed.
    10  func f1[K1 comparable, E1 any](m1 map[K1]E1) {}
    11  
    12  func f2[M2 map[string]int](m2 M2) {
    13  	f1(m2)
    14  }
    15  
    16  // The core type of M3 unifies with the type of m1
    17  // during function argument type inference.
    18  // M3's constraint is named.
    19  type Map3 map[string]int
    20  
    21  func f3[M3 Map3](m3 M3) {
    22  	f1(m3)
    23  }
    24  
    25  // The core type of M5 unifies with the core type of M4
    26  // during constraint type inference.
    27  func f4[M4 map[K4]int, K4 comparable](m4 M4) {}
    28  
    29  func f5[M5 map[K5]int, K5 comparable](m5 M5) {
    30  	f4(m5)
    31  }
    32  
    33  // test case from issue
    34  
    35  func Copy[MC ~map[KC]VC, KC comparable, VC any](dst, src MC) {
    36  	for k, v := range src {
    37  		dst[k] = v
    38  	}
    39  }
    40  
    41  func Merge[MM ~map[KM]VM, KM comparable, VM any](ms ...MM) MM {
    42  	result := MM{}
    43  	for _, m := range ms {
    44  		Copy(result, m)
    45  	}
    46  	return result
    47  }
    48
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