golang issue50690a 代码
文件路径：/test/typeparam/issue50690a.go
/ run
/ Copyright 2022 The Go Authors. All rights reserved.
/ Use of this source code is governed by a BSD-style
/ license that can be found in the LICENSE file.
package main
import (
"fmt"
)
/ Numeric expresses a type constraint satisfied by any numeric type.
type Numeric interface {
~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 |
~int | ~int8 | ~int16 | ~int32 | ~int64 |
~float32 | ~float64 |
~complex64 | ~complex128
}
/ Sum returns the sum of the provided arguments.
func Sum[T Numeric](args ...T) T {
var sum T
for i := 0; i < len(args); i++ {
sum += args[i]
}
return sum
}
/ Ledger is an identifiable, financial record.
type Ledger[T ~string, K Numeric] struct {
/ ID identifies the ledger.
ID_ T
/ Amounts is a list of monies associated with this ledger.
Amounts_ []K
/ SumFn is a function that can be used to sum the amounts
/ in this ledger.
SumFn_ func(...K) K
}
/ Field accesses through type parameters are disabled
/ until we have a more thorough understanding of the
/ implications on the spec. See issue #51576.
/ Use accessor methods instead.
func (l Ledger[T, _]) ID() T { return l.ID_ }
func (l Ledger[_, K]) Amounts() []K { return l.Amounts_ }
func (l Ledger[_, K]) SumFn() func(...K) K { return l.SumFn_ }
func PrintLedger[
T ~string,
K Numeric,
L interface {
~struct {
ID_ T
Amounts_ []K
SumFn_ func(...K) K
}
ID() T
Amounts() []K
SumFn() func(...K) K
},
](l L) {
fmt.Printf("%s has a sum of %v\n", l.ID(), l.SumFn()(l.Amounts()...))
}
func main() {
PrintLedger(Ledger[string, int]{
ID_: "fake",
Amounts_: []int{1, 2, 3},
SumFn_: Sum[int],
})
}