Fix exception accessing indexer property for field interceptor proxy (#3358)

Fixes #3354

Author: bahusoid

src/NHibernate.Test/Async/LazyProperty/LazyPropertyFixture.cs

@@ -230,6 +230,9 @@ public async Task CanGetValueForNonLazyPropertyAsync()
 				Assert.That(book.Name, Is.EqualTo("some name"));
 				Assert.That(book.FieldInterceptor, Is.EqualTo("Why not that name?"));
 				Assert.That(NHibernateUtil.IsPropertyInitialized(book, "ALotOfText"), Is.False);
+				//GH-3354 Exception accessing indexer property
+				Assert.That(book[0], Is.EqualTo(0));
+				Assert.DoesNotThrow(() => book[0] = 0);
 			}
 		}
 

src/NHibernate.Test/LazyProperty/Book.cs

@@ -28,5 +28,11 @@ public virtual byte[] NoSetterImage
 		public virtual string FieldInterceptor { get; set; }
 
 		public virtual IList<Word> Words { get; set; }
+
+		public virtual int this[int i]
+		{
+			get { return i;}
+			set { }
+		}
 	}
 }

src/NHibernate.Test/LazyProperty/LazyPropertyFixture.cs

@@ -225,6 +225,9 @@ public void CanGetValueForNonLazyProperty()
 				Assert.That(book.Name, Is.EqualTo("some name"));
 				Assert.That(book.FieldInterceptor, Is.EqualTo("Why not that name?"));
 				Assert.That(NHibernateUtil.IsPropertyInitialized(book, "ALotOfText"), Is.False);
+				//GH-3354 Exception accessing indexer property
+				Assert.That(book[0], Is.EqualTo(0));
+				Assert.DoesNotThrow(() => book[0] = 0);
 			}
 		}
 

src/NHibernate/Proxy/FieldInterceptorProxyBuilder.cs

@@ -94,11 +94,11 @@ public static TypeInfo CreateProxyType(System.Type baseType)
 
 		private static void CreateProxiedMethod(TypeBuilder typeBuilder, MethodInfo method, FieldInfo fieldInterceptorField)
 		{
-			if (ReflectHelper.IsPropertyGet(method))
+			if (ReflectHelper.IsPropertyGet(method) && method.GetParameters().Length == 0)
 			{
 				ImplementGet(typeBuilder, method, fieldInterceptorField);
 			}
-			else if (ReflectHelper.IsPropertySet(method))
+			else if (ReflectHelper.IsPropertySet(method) && method.GetParameters().Length == 1)
 			{
 				ImplementSet(typeBuilder, method, fieldInterceptorField);
 			}