chore: reimplement TypedValue by atomic.Pointer

Author: wwqgtxx

common/atomic/value.go

@@ -11,19 +11,7 @@ func DefaultValue[T any]() T {
 }
 
 type TypedValue[T any] struct {
-	_     noCopy
-	value atomic.Value
-}
-
-// tValue is a struct with determined type to resolve atomic.Value usages with interface types
-// https://github.com/golang/go/issues/22550
-//
-// The intention to have an atomic value store for errors. However, running this code panics:
-// panic: sync/atomic: store of inconsistently typed value into Value
-// This is because atomic.Value requires that the underlying concrete type be the same (which is a reasonable expectation for its implementation).
-// When going through the atomic.Value.Store method call, the fact that both these are of the error interface is lost.
-type tValue[T any] struct {
-	value T
+	value atomic.Pointer[T]
 }
 
 func (t *TypedValue[T]) Load() T {
@@ -36,27 +24,36 @@ func (t *TypedValue[T]) LoadOk() (_ T, ok bool) {
 	if value == nil {
 		return DefaultValue[T](), false
 	}
-	return value.(tValue[T]).value, true
+	return *value, true
 }
 
 func (t *TypedValue[T]) Store(value T) {
-	t.value.Store(tValue[T]{value})
+	t.value.Store(&value)
 }
 
 func (t *TypedValue[T]) Swap(new T) T {
-	old := t.value.Swap(tValue[T]{new})
+	old := t.value.Swap(&new)
 	if old == nil {
 		return DefaultValue[T]()
 	}
-	return old.(tValue[T]).value
+	return *old
 }
 
 func (t *TypedValue[T]) CompareAndSwap(old, new T) bool {
-	return t.value.CompareAndSwap(tValue[T]{old}, tValue[T]{new}) ||
-		// In the edge-case where [atomic.Value.Store] is uninitialized
-		// and trying to compare with the zero value of T,
-		// then compare-and-swap with the nil any value.
-		(any(old) == any(DefaultValue[T]()) && t.value.CompareAndSwap(any(nil), tValue[T]{new}))
+	for {
+		currentP := t.value.Load()
+		currentValue := DefaultValue[T]()
+		if currentP != nil {
+			currentValue = *currentP
+		}
+		// Compare old and current via runtime equality check.
+		if any(currentValue) != any(old) {
+			return false
+		}
+		if t.value.CompareAndSwap(currentP, &new) {
+			return true
+		}
+	}
 }
 
 func (t *TypedValue[T]) MarshalJSON() ([]byte, error) {
@@ -89,9 +86,3 @@ func NewTypedValue[T any](t T) (v TypedValue[T]) {
 	v.Store(t)
 	return
 }
-
-type noCopy struct{}
-
-// Lock is a no-op used by -copylocks checker from `go vet`.
-func (*noCopy) Lock()   {}
-func (*noCopy) Unlock() {}

common/atomic/value_test.go

@@ -7,20 +7,6 @@ import (
 )
 
 func TestTypedValue(t *testing.T) {
-	{
-		// Always wrapping should not allocate for simple values
-		// because tValue[T] has the same memory layout as T.
-		var v TypedValue[bool]
-		bools := []bool{true, false}
-		if n := int(testing.AllocsPerRun(1000, func() {
-			for _, b := range bools {
-				v.Store(b)
-			}
-		})); n != 0 {
-			t.Errorf("AllocsPerRun = %d, want 0", n)
-		}
-	}
-
 	{
 		var v TypedValue[int]
 		got, gotOk := v.LoadOk()