hash/maphash: hash channels in purego version of maphash.Comparable

This change makes purego implementation of maphash.Comparable consistent
with the one in runtime and fixes hashing of channels.

Fixes #73657

Change-Id: If78a21d996f0c20c0224d4014e4a4177b09c3aa3
GitHub-Last-Rev: 2537216
GitHub-Pull-Request: #73660
Reviewed-on: https://go-review.googlesource.com/c/go/+/671655
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: qiu laidongfeng2 <2645477756@qq.com>

Author: Snawoot

src/hash/maphash/maphash_purego.go

@@ -161,7 +161,7 @@ func appendT(h *Hash, v reflect.Value) {
 	case reflect.Bool:
 		h.WriteByte(btoi(v.Bool()))
 		return
-	case reflect.UnsafePointer, reflect.Pointer:
+	case reflect.UnsafePointer, reflect.Pointer, reflect.Chan:
 		var buf [8]byte
 		// because pointing to the abi.Escape call in comparableReady,
 		// So this is ok to hash pointer,

src/hash/maphash/maphash_test.go

@@ -254,12 +254,17 @@ func TestComparable(t *testing.T) {
 	}
 	testComparable(t, s1, s2)
 	testComparable(t, s1.s, s2.s)
+	c1 := make(chan struct{})
+	c2 := make(chan struct{})
+	testComparable(t, c1, c1)
+	testComparable(t, chan struct{}(nil))
 	testComparable(t, float32(0), negativeZero[float32]())
 	testComparable(t, float64(0), negativeZero[float64]())
 	testComparableNoEqual(t, math.NaN(), math.NaN())
 	testComparableNoEqual(t, [2]string{"a", ""}, [2]string{"", "a"})
 	testComparableNoEqual(t, struct{ a, b string }{"foo", ""}, struct{ a, b string }{"", "foo"})
 	testComparableNoEqual(t, struct{ a, b any }{int(0), struct{}{}}, struct{ a, b any }{struct{}{}, int(0)})
+	testComparableNoEqual(t, c1, c2)
 }
 
 func testComparableNoEqual[T comparable](t *testing.T, v1, v2 T) {