Fix memory leak

Author: oformaniuk

source/Handlebars/Compiler/Middlewares/ClosureExpressionMiddleware.cs

@@ -11,22 +11,25 @@ internal class ClosureExpressionMiddleware : IExpressionMiddleware
     {
         public Expression<T> Invoke<T>(Expression<T> expression) where T : Delegate
         {
-            using var container = GenericObjectPool<List<ConstantExpression>>.Shared.Use();
-            var constants = container.Value;
+            var constants = new List<ConstantExpression>();
             var closureCollectorVisitor = new ClosureCollectorVisitor(constants);
             expression = (Expression<T>) closureCollectorVisitor.Visit(expression);
 
             if (constants.Count == 0) return expression;
-            
-            using var closureBuilder = ClosureBuilder.Create();
-            for (var index = 0; index < constants.Count; index++)
+
+            KeyValuePair<ParameterExpression, Dictionary<Expression, Expression>> closureDefinition;
+            Closure closure;
+            using (var closureBuilder = ClosureBuilder.Create())
             {
-                var value = constants[index];
-                closureBuilder.Add(value);
+                for (var index = 0; index < constants.Count; index++)
+                {
+                    var value = constants[index];
+                    closureBuilder.Add(value);
+                }
+
+                closureDefinition = closureBuilder.Build(out closure);
             }
 
-            var closureDefinition = closureBuilder.Build(out var closure);
-            
             var closureVisitor = new ClosureVisitor(closureDefinition);
             expression = (Expression<T>) closureVisitor.Visit(expression);
 

source/Handlebars/Pools/GenericObjectPool.cs

@@ -1,13 +1,10 @@
-using System;
-
-namespace HandlebarsDotNet.Pools
+namespace HandlebarsDotNet.Pools
 {
     internal class GenericObjectPool<T> : InternalObjectPool<T, GenericObjectPool<T>.Policy> 
         where T : class, new()
     {
-        private static readonly Lazy<GenericObjectPool<T>> Instance = new(() => new GenericObjectPool<T>());
-        public static GenericObjectPool<T> Shared => Instance.Value;
-        
+        public static GenericObjectPool<T> Shared { get; } = new();
+
         private GenericObjectPool() : base(new Policy()) { }
 
         public readonly struct Policy : IInternalObjectPoolPolicy<T>