From 6e57cd4ebe6db3b9537e958a9d358bae148a9fe1 Mon Sep 17 00:00:00 2001
From: Jamiras <jamirasmt@gmail.com>
Date: Sat, 13 Dec 2025 15:41:51 -0700
Subject: [PATCH] ensure 'this' gets captured for lambda expressions

---
 .../ClassMemberReferenceExpression.cs         |  9 ++----
 .../ClassDefinitionExpressionTests.cs         | 18 ++++++++++--
 .../ClassMemberReferenceExpressionTests.cs    | 28 +++++++++++++++++++
 3 files changed, 47 insertions(+), 8 deletions(-)

diff --git a/Source/Parser/Expressions/ClassMemberReferenceExpression.cs b/Source/Parser/Expressions/ClassMemberReferenceExpression.cs
index 0c9be692..284f2482 100644
--- a/Source/Parser/Expressions/ClassMemberReferenceExpression.cs
+++ b/Source/Parser/Expressions/ClassMemberReferenceExpression.cs
@@ -224,12 +224,9 @@ void INestedExpressions.GetDependencies(HashSet<string> dependencies)
             if (nested != null)
                 nested.GetDependencies(dependencies);
 
-            if (Variable != null && Variable.Name != "this")
-            {
-                nested = Variable as INestedExpressions;
-                if (nested != null)
-                    nested.GetDependencies(dependencies);
-            }
+            nested = Variable as INestedExpressions;
+            if (nested != null)
+                nested.GetDependencies(dependencies);
 
             // we can't know the type of the source object, so just
             // declare dependance on all fields matching the provided name
diff --git a/Tests/Parser/Expressions/ClassDefinitionExpressionTests.cs b/Tests/Parser/Expressions/ClassDefinitionExpressionTests.cs
index 7368f53a..0866fb72 100644
--- a/Tests/Parser/Expressions/ClassDefinitionExpressionTests.cs
+++ b/Tests/Parser/Expressions/ClassDefinitionExpressionTests.cs
@@ -78,6 +78,18 @@ public void TestParseFunction()
             Assert.That(expr.ToString(), Is.EqualTo("class Entity(1 field, 1 function)"));
         }
 
+        [Test]
+        public void TestParseLambdaReference()
+        {
+            var expr = Parse(
+                "class Entity {\n" +
+                "  addr = 4\n" +
+                "  function hp() => sum_of(range(0, 5), (i) => i < this.addr)\n" +
+                "}");
+            Assert.That(expr.Name.Name, Is.EqualTo("Entity"));
+            Assert.That(expr.ToString(), Is.EqualTo("class Entity(1 field, 1 function)"));
+        }
+
         [Test]
         public void TestParseErrorInsideField()
         {
@@ -263,8 +275,9 @@ public void TestGetDependencies()
             var dependencies = new HashSet<string>();
             ((INestedExpressions)expr).GetDependencies(dependencies);
 
-            Assert.That(dependencies.Count, Is.EqualTo(3));
+            Assert.That(dependencies.Count, Is.EqualTo(4));
             Assert.That(dependencies.Contains("word"));
+            Assert.That(dependencies.Contains("this"));
             Assert.That(dependencies.Contains(".addr"));
             Assert.That(dependencies.Contains("global_var"));
         }
@@ -281,8 +294,9 @@ public void TestGetDependenciesNested()
             var dependencies = new HashSet<string>();
             ((INestedExpressions)expr).GetDependencies(dependencies);
 
-            Assert.That(dependencies.Count, Is.EqualTo(5));
+            Assert.That(dependencies.Count, Is.EqualTo(6));
             Assert.That(dependencies.Contains("word"));
+            Assert.That(dependencies.Contains("this"));
             Assert.That(dependencies.Contains(".addr"));
             Assert.That(dependencies.Contains(".x"));
             Assert.That(dependencies.Contains("global"));
diff --git a/Tests/Parser/Expressions/ClassMemberReferenceExpressionTests.cs b/Tests/Parser/Expressions/ClassMemberReferenceExpressionTests.cs
index 8a3a01e0..1c685292 100644
--- a/Tests/Parser/Expressions/ClassMemberReferenceExpressionTests.cs
+++ b/Tests/Parser/Expressions/ClassMemberReferenceExpressionTests.cs
@@ -410,5 +410,33 @@ public void TestReadFromNestedIndexNonArray()
             var error = assign.Execute(scope);
             ExpressionTests.AssertError(error, "Cannot index integer: this.points");
         }
+
+        [Test]
+        public void TestLambdaReference()
+        {
+            var entityClass = ExpressionTests.Parse<ClassDefinitionExpression>(
+                "class Entity {\n" +
+                "  addr = 2\n" +
+                "  function multiplyBy6() => sum_of(range(0, 5), (i) => this.addr)\n" +
+                "}");
+
+            var scope = new InterpreterScope(AchievementScriptInterpreter.GetGlobalScope());
+            scope.Context = new AchievementScriptContext();
+            entityClass.Execute(scope);
+
+            var constructor = new FunctionCallExpression("Entity", new ExpressionBase[] { new IntegerConstantExpression(4) });
+            var entity = constructor.Evaluate(scope);
+            Assert.That(entity, Is.InstanceOf<ClassInstanceExpression>());
+
+            scope.AssignVariable(new VariableExpression("e"), entity);
+
+            var assign = Parse("n = e.multiplyBy6()");
+            var error = assign.Execute(scope);
+            Assert.That(error, Is.Null);
+
+            var n = scope.GetVariable("n");
+            Assert.That(n, Is.InstanceOf<IntegerConstantExpression>());
+            Assert.That(((IntegerConstantExpression)n).Value, Is.EqualTo(24)); // 4+4+4+4+4+4
+        }
     }
 }