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// run -gcflags=-G=3
// Copyright 2021 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"
"reflect"
)
type Number interface {
~int | ~int8 | ~int16 | ~int32 | ~int64 | ~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr | ~float32 | ~float64
}
type MySlice []int
type MyFloatSlice []float64
type _SliceOf[E any] interface {
type []E
}
func _DoubleElems[S _SliceOf[E], E Number](s S) S {
r := make(S, len(s))
for i, v := range s {
r[i] = v + v
}
return r
}
// Test use of untyped constant in an expression with a generically-typed parameter
func _DoubleElems2[S _SliceOf[E], E Number](s S) S {
r := make(S, len(s))
for i, v := range s {
r[i] = v * 2
}
return r
}
func main() {
arg := MySlice{1, 2, 3}
want := MySlice{2, 4, 6}
got := _DoubleElems[MySlice, int](arg)
if !reflect.DeepEqual(got, want) {
panic(fmt.Sprintf("got %s, want %s", got, want))
}
// constraint type inference
got = _DoubleElems[MySlice](arg)
if !reflect.DeepEqual(got, want) {
panic(fmt.Sprintf("got %s, want %s", got, want))
}
got = _DoubleElems(arg)
if !reflect.DeepEqual(got, want) {
panic(fmt.Sprintf("got %s, want %s", got, want))
}
farg := MyFloatSlice{1.2, 2.0, 3.5}
fwant := MyFloatSlice{2.4, 4.0, 7.0}
fgot := _DoubleElems(farg)
if !reflect.DeepEqual(fgot, fwant) {
panic(fmt.Sprintf("got %s, want %s", fgot, fwant))
}
fgot = _DoubleElems2(farg)
if !reflect.DeepEqual(fgot, fwant) {
panic(fmt.Sprintf("got %s, want %s", fgot, fwant))
}
}
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