simplify & fix db tests

src/db/lib.rs

@@ -35,10 +35,11 @@ pub struct Error(pub Cow<'static, str>);
 
 pub type Result<T> = std::result::Result<T, Error>;
 
+#[derive(Debug, Error)]
+#[error(display = "{}", _0)]
 pub struct TxOpError(pub(crate) Error);
 pub type TxOpResult<T> = std::result::Result<T, TxOpError>;
 
-#[derive(Debug)]
 pub enum TxError<E> {
 	Abort(E),
 	Db(Error),

src/db/lmdb_adapter.rs

@@ -203,12 +203,12 @@ impl IDb for LmdbDb {
 
 // ----
 
-struct LmdbTx<'a, 'db> {
-	trees: &'db [Database],
+struct LmdbTx<'a> {
+	trees: &'a [Database],
 	tx: RwTxn<'a, 'a>,
 }
 
-impl<'a, 'db> LmdbTx<'a, 'db> {
+impl<'a> LmdbTx<'a> {
 	fn get_tree(&self, i: usize) -> TxOpResult<&Database> {
 		self.trees.get(i).ok_or_else(|| {
 			TxOpError(Error(
@@ -218,7 +218,7 @@ impl<'a, 'db> LmdbTx<'a, 'db> {
 	}
 }
 
-impl<'a, 'db> ITx for LmdbTx<'a, 'db> {
+impl<'a> ITx for LmdbTx<'a> {
 	fn get(&self, tree: usize, key: &[u8]) -> TxOpResult<Option<Value>> {
 		let tree = self.get_tree(tree)?;
 		match tree.get(&self.tx, key)? {