Indexes over bool fields are now created with the correct expression

LiteDB/Client/Database/Collections/Index.cs

@@ -67,7 +67,7 @@ public bool EnsureIndex<K>(string name, Expression<Func<T, K>> keySelector, bool
         /// </summary>
         private BsonExpression GetIndexExpression<K>(Expression<Func<T, K>> keySelector)
         {
-            var expression = _mapper.GetExpression(keySelector);
+            var expression = _mapper.GetIndexExpression(keySelector);
 
             if (typeof(K).IsEnumerable() && expression.IsScalar == true)
             {

LiteDB/Client/Mapper/BsonMapper.cs

@@ -184,6 +184,20 @@ public BsonExpression GetExpression<T, K>(Expression<Func<T, K>> predicate)
             return expr;
         }
 
+        /// <summary>
+        /// Resolve LINQ expression into BsonExpression (for index only)
+        /// </summary>
+        public BsonExpression GetIndexExpression<T, K>(Expression<Func<T, K>> predicate)
+        {
+            var visitor = new LinqExpressionVisitor(this, predicate);
+
+            var expr = visitor.Resolve(false);
+
+            LOG($"`{predicate.ToString()}` -> `{expr.Source}`", "LINQ");
+
+            return expr;
+        }
+
         #endregion
 
         #region Predefinded Property Resolvers
@@ -514,7 +528,7 @@ private static void RegisterDbRefItem(BsonMapper mapper, MemberMapper member, IT
                     }
 
                     return m.Deserialize(entity.ForType, doc);
-                    
+
                 }
                 else
                 {