Merge bitcoindevkit/bdk#1874: fix(wallet): allow PersistedWallet to be Send + Sync

14251a4 fix(wallet): allow PersistedWallet<P> to be Send + Sync even if P is !Sync (Steve Myers)

Pull request description:

  ### Description

  fixes #1873 based on solution proposed by @praveenperera .

  ### Notes to the reviewers

  This is not a breaking change since it's only changing the internal `_marker` field's type.

  ### Changelog notice

  - Fix PersistedWallet to be Send + Sync, even when used with a !Sync persister type such as rusqlite::Connection.

  ### Checklists

  #### All Submissions:

  * [x] I've signed all my commits
  * [x] I followed the [contribution guidelines](https://github.com/bitcoindevkit/bdk/blob/master/CONTRIBUTING.md)
  * [x] I ran `cargo fmt` and `cargo clippy` before committing

  #### Bugfixes:

  * [ ] This pull request breaks the existing API
  * [x] I've added tests to reproduce the issue which are now passing
  * [x] I'm linking the issue being fixed by this PR

ACKs for top commit:
  ValuedMammal:
    ACK 14251a4

Tree-SHA512: 8ce8ad7d9b2d962114e225074b485bc91671164fe2f2fcd59f48a6c4f53a885bb215d0017584292629fa02b5ca19a67a40a7855fcd4c2490fefd2b3be65f717f

Author: notmandatory

crates/wallet/src/wallet/persisted.rs

@@ -120,7 +120,7 @@ pub trait AsyncWalletPersister {
 #[derive(Debug)]
 pub struct PersistedWallet<P> {
     inner: Wallet,
-    marker: PhantomData<P>,
+    _marker: PhantomData<fn(&mut P)>,
 }
 
 impl<P> Deref for PersistedWallet<P> {
@@ -155,7 +155,7 @@ impl<P: WalletPersister> PersistedWallet<P> {
         }
         Ok(Self {
             inner,
-            marker: PhantomData,
+            _marker: PhantomData,
         })
     }
 
@@ -169,7 +169,7 @@ impl<P: WalletPersister> PersistedWallet<P> {
             .map(|opt| {
                 opt.map(|inner| PersistedWallet {
                     inner,
-                    marker: PhantomData,
+                    _marker: PhantomData,
                 })
             })
             .map_err(LoadWithPersistError::InvalidChangeSet)
@@ -214,7 +214,7 @@ impl<P: AsyncWalletPersister> PersistedWallet<P> {
         }
         Ok(Self {
             inner,
-            marker: PhantomData,
+            _marker: PhantomData,
         })
     }
 
@@ -230,7 +230,7 @@ impl<P: AsyncWalletPersister> PersistedWallet<P> {
             .map(|opt| {
                 opt.map(|inner| PersistedWallet {
                     inner,
-                    marker: PhantomData,
+                    _marker: PhantomData,
                 })
             })
             .map_err(LoadWithPersistError::InvalidChangeSet)

crates/wallet/tests/wallet.rs

@@ -12,7 +12,9 @@ use bdk_wallet::psbt::PsbtUtils;
 use bdk_wallet::signer::{SignOptions, SignerError};
 use bdk_wallet::test_utils::*;
 use bdk_wallet::tx_builder::AddForeignUtxoError;
-use bdk_wallet::{AddressInfo, Balance, ChangeSet, Update, Wallet, WalletPersister, WalletTx};
+use bdk_wallet::{
+    AddressInfo, Balance, ChangeSet, PersistedWallet, Update, Wallet, WalletPersister, WalletTx,
+};
 use bdk_wallet::{KeychainKind, LoadError, LoadMismatch, LoadWithPersistError};
 use bitcoin::constants::{ChainHash, COINBASE_MATURITY};
 use bitcoin::hashes::Hash;
@@ -4209,6 +4211,7 @@ fn test_tx_cancellation() {
 fn test_thread_safety() {
     fn thread_safe<T: Send + Sync>() {}
     thread_safe::<Wallet>(); // compiles only if true
+    thread_safe::<PersistedWallet<bdk_chain::rusqlite::Connection>>();
 }
 
 #[test]