1 files changed, 95 insertions, 0 deletions
diff --git a/test/typeparam/ordered.go b/test/typeparam/ordered.go
new file mode 100644
index 0000000..d304298
--- /dev/null
+++ b/test/typeparam/ordered.go
@@ -0,0 +1,95 @@
+// run
+
+// 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"
+	"math"
+	"sort"
+)
+
+type Ordered interface {
+	~int | ~int8 | ~int16 | ~int32 | ~int64 |
+		~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr |
+		~float32 | ~float64 |
+		~string
+}
+
+type orderedSlice[Elem Ordered] []Elem
+
+func (s orderedSlice[Elem]) Len() int { return len(s) }
+func (s orderedSlice[Elem]) Less(i, j int) bool {
+	if s[i] < s[j] {
+		return true
+	}
+	isNaN := func(f Elem) bool { return f != f }
+	if isNaN(s[i]) && !isNaN(s[j]) {
+		return true
+	}
+	return false
+}
+func (s orderedSlice[Elem]) Swap(i, j int) { s[i], s[j] = s[j], s[i] }
+
+func _OrderedSlice[Elem Ordered](s []Elem) {
+	sort.Sort(orderedSlice[Elem](s))
+}
+
+var ints = []int{74, 59, 238, -784, 9845, 959, 905, 0, 0, 42, 7586, -5467984, 7586}
+var float64s = []float64{74.3, 59.0, math.Inf(1), 238.2, -784.0, 2.3, math.NaN(), math.NaN(), math.Inf(-1), 9845.768, -959.7485, 905, 7.8, 7.8}
+var strings = []string{"", "Hello", "foo", "bar", "foo", "f00", "%*&^*&^&", "***"}
+
+func TestSortOrderedInts() bool {
+	return testOrdered("ints", ints, sort.Ints)
+}
+
+func TestSortOrderedFloat64s() bool {
+	return testOrdered("float64s", float64s, sort.Float64s)
+}
+
+func TestSortOrderedStrings() bool {
+	return testOrdered("strings", strings, sort.Strings)
+}
+
+func testOrdered[Elem Ordered](name string, s []Elem, sorter func([]Elem)) bool {
+	s1 := make([]Elem, len(s))
+	copy(s1, s)
+	s2 := make([]Elem, len(s))
+	copy(s2, s)
+	_OrderedSlice(s1)
+	sorter(s2)
+	ok := true
+	if !sliceEq(s1, s2) {
+		fmt.Printf("%s: got %v, want %v", name, s1, s2)
+		ok = false
+	}
+	for i := len(s1) - 1; i > 0; i-- {
+		if s1[i] < s1[i-1] {
+			fmt.Printf("%s: element %d (%v) < element %d (%v)", name, i, s1[i], i-1, s1[i-1])
+			ok = false
+		}
+	}
+	return ok
+}
+
+func sliceEq[Elem Ordered](s1, s2 []Elem) bool {
+	for i, v1 := range s1 {
+		v2 := s2[i]
+		if v1 != v2 {
+			isNaN := func(f Elem) bool { return f != f }
+			if !isNaN(v1) || !isNaN(v2) {
+				return false
+			}
+		}
+	}
+	return true
+}
+
+func main() {
+	if !TestSortOrderedInts() || !TestSortOrderedFloat64s() || !TestSortOrderedStrings() {
+		panic("failure")
+	}
+}