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// Copyright 2020 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 funcInference
import "strconv"
type any interface{}
func f0[A any, B interface{*C}, C interface{*D}, D interface{*A}](A, B, C, D) {}
func _() {
f := f0[string]
f("a", nil, nil, nil)
f0("a", nil, nil, nil)
}
func f1[A any, B interface{*A}](A, B) {}
func _() {
f := f1[int]
f(int(0), new(int))
f1(int(0), new(int))
}
func f2[A any, B interface{[]A}](A, B) {}
func _() {
f := f2[byte]
f(byte(0), []byte{})
f2(byte(0), []byte{})
}
// Embedding stand-alone type parameters is not permitted for now. Disabled.
// func f3[A any, B interface{~C}, C interface{~*A}](A, B, C)
// func _() {
// f := f3[int]
// var x int
// f(x, &x, &x)
// f3(x, &x, &x)
// }
func f4[A any, B interface{[]C}, C interface{*A}](A, B, C) {}
func _() {
f := f4[int]
var x int
f(x, []*int{}, &x)
f4(x, []*int{}, &x)
}
func f5[A interface{struct{b B; c C}}, B any, C interface{*B}](x B) A { panic(0) }
func _() {
x := f5(1.2)
var _ float64 = x.b
var _ float64 = *x.c
}
func f6[A any, B interface{~struct{f []A}}](B) A { panic(0) }
func _() {
x := f6(struct{f []string}{})
var _ string = x
}
func f7[A interface{*B}, B interface{~*A}]() {}
// More realistic examples
func Double[S interface{ ~[]E }, E interface{ ~int | ~int8 | ~int16 | ~int32 | ~int64 }](s S) S {
r := make(S, len(s))
for i, v := range s {
r[i] = v + v
}
return r
}
type MySlice []int
var _ = Double(MySlice{1})
// From the draft design.
type Setter[B any] interface {
Set(string)
*B
}
func FromStrings[T interface{}, PT Setter[T]](s []string) []T {
result := make([]T, len(s))
for i, v := range s {
// The type of &result[i] is *T which is in the type set
// of Setter, so we can convert it to PT.
p := PT(&result[i])
// PT has a Set method.
p.Set(v)
}
return result
}
type Settable int
func (p *Settable) Set(s string) {
i, _ := strconv.Atoi(s) // real code should not ignore the error
*p = Settable(i)
}
var _ = FromStrings[Settable]([]string{"1", "2"})
// Suitable error message when the type parameter is provided (rather than inferred).
func f8[P, Q any](P, Q) {}
func _(s string) {
f8[int](s /* ERROR "cannot use s (variable of type string) as int value in argument to f8[int]" */ , s)
}