| // 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 list |
| // 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"}) |