[topology] move IsStateValidOrAttaching to Neighbor (#4419)

src/core/thread/topology.cpp

@@ -41,18 +41,7 @@
 
 namespace ot {
 
-void Neighbor::GenerateChallenge(void)
-{
-    Random::Crypto::FillBuffer(mValidPending.mPending.mChallenge, sizeof(mValidPending.mPending.mChallenge));
-}
-
-void Child::Clear(void)
-{
-    memset(reinterpret_cast<void *>(this), 0, sizeof(Child));
-    SetState(kStateInvalid);
-}
-
-bool Child::IsStateValidOrAttaching(void) const
+bool Neighbor::IsStateValidOrAttaching(void) const
 {
     bool rval = false;
 
@@ -75,6 +64,17 @@ bool Child::IsStateValidOrAttaching(void) const
     return rval;
 }
 
+void Neighbor::GenerateChallenge(void)
+{
+    Random::Crypto::FillBuffer(mValidPending.mPending.mChallenge, sizeof(mValidPending.mPending.mChallenge));
+}
+
+void Child::Clear(void)
+{
+    memset(reinterpret_cast<void *>(this), 0, sizeof(Child));
+    SetState(kStateInvalid);
+}
+
 void Child::ClearIp6Addresses(void)
 {
     memset(mMeshLocalIid, 0, sizeof(mMeshLocalIid));

src/core/thread/topology.hpp

@@ -157,6 +157,17 @@ public:
      */
     bool IsStateValidOrRestoring(void) const { return (mState == kStateValid) || IsStateRestoring(); }
 
+    /**
+     * This method indicates if the neighbor state is valid, attaching, or restored.
+     *
+     * The states `kStateRestored`, `kStateChildIdRequest`, `kStateChildUpdateRequest`, `kStateValid`, and
+     * `kStateLinkRequest` are considered as valid, attaching, or restored.
+     *
+     * @returns TRUE if the neighbor state is valid, attaching, or restored, FALSE otherwise.
+     *
+     */
+    bool IsStateValidOrAttaching(void) const;
+
     /**
      * This method gets the device mode flags.
      *
@@ -480,17 +491,6 @@ public:
      */
     void Clear(void);
 
-    /**
-     * This method indicates if the child state is valid or being attached or being restored.
-     *
-     * The states `kStateRestored`, `kStateChildIdRequest`, `kStateChildUpdateRequest`, `kStateValid`, (and
-     * `kStateLinkRequest) are considered as attached or being restored.
-     *
-     * @returns TRUE if the child is attached or being restored.
-     *
-     */
-    bool IsStateValidOrAttaching(void) const;
-
     /**
      * This method clears the IPv6 address list for the child.
      *