Fix scoping issues with default function parameters

Author: CallumDev

src/MoonSharp.Interpreter/Execution/Scopes/BuildTimeScope.cs

@@ -11,10 +11,15 @@ internal class BuildTimeScope
 		List<BuildTimeScopeFrame> m_Frames = new List<BuildTimeScopeFrame>();
 		List<IClosureBuilder> m_ClosureBuilders = new List<IClosureBuilder>();
 
-		public void PushFunction(IClosureBuilder closureBuilder, bool hasVarArgs)
+		public void PushFunction(IClosureBuilder closureBuilder)
 		{
 			m_ClosureBuilders.Add(closureBuilder);
-			m_Frames.Add(new BuildTimeScopeFrame(hasVarArgs));
+			m_Frames.Add(new BuildTimeScopeFrame());
+		}
+
+		public void SetHasVarArgs()
+		{
+			m_Frames.Last().HasVarArgs = true;
 		}
 
 		public void PushBlock()

src/MoonSharp.Interpreter/Execution/Scopes/BuildTimeScopeFrame.cs

@@ -10,11 +10,10 @@ internal class BuildTimeScopeFrame
 		BuildTimeScopeBlock m_ScopeTreeHead;
 		RuntimeScopeFrame m_ScopeFrame = new RuntimeScopeFrame();
 
-		public bool HasVarArgs { get; private set;}
+		public bool HasVarArgs { get; set;}
 
-		internal BuildTimeScopeFrame(bool hasVarArgs)
+		internal BuildTimeScopeFrame()
 		{
-			HasVarArgs = hasVarArgs;
 			m_ScopeTreeHead = m_ScopeTreeRoot = new BuildTimeScopeBlock(null);
 		}
 

src/MoonSharp.Interpreter/Tree/Expressions/FunctionDefinitionExpression.cs

@@ -43,6 +43,23 @@ private FunctionDefinitionExpression(ScriptLoadingContext lcontext, bool pushSel
 			if (m_UsesGlobalEnv = usesGlobalEnv)
 				CheckTokenType(lcontext, TokenType.Function);
 
+			
+			// create scope
+			// This needs to be up here to allow for arguments to correctly close over ENV
+			// Arguments, however, must come before any other local definitions to avoid closing
+			// over uninitialised variables. (Note for hoisting).
+			lcontext.Scope.PushFunction(this);
+
+			if (m_UsesGlobalEnv)
+			{
+				m_Env = lcontext.Scope.DefineLocal(WellKnownSymbols.ENV);
+			}
+			else
+			{
+				lcontext.Scope.ForceEnvUpValue();
+			}
+			
+			// Parse arguments
 			// here lexer should be at the '(' or at the '|'
 			//Token openRound = CheckTokenType(lcontext, isLambda ? TokenType.Lambda : TokenType.Brk_Open_Round);
 
@@ -78,19 +95,10 @@ private FunctionDefinitionExpression(ScriptLoadingContext lcontext, bool pushSel
 
 			m_Begin = openRound.GetSourceRefUpTo(lcontext.Lexer.Current);
 
-			// create scope
-			lcontext.Scope.PushFunction(this, m_HasVarArgs);
-
-			if (m_UsesGlobalEnv)
-			{
-				m_Env = lcontext.Scope.DefineLocal(WellKnownSymbols.ENV);
-			}
-			else
-			{
-				lcontext.Scope.ForceEnvUpValue();
-			}
 
 			m_ParamNames = DefineArguments(paramnames, lcontext);
+			
+			if(m_HasVarArgs) lcontext.Scope.SetHasVarArgs(); //Moved here
 
 			if(isLambda)
 				m_Statement = CreateLambdaBody(lcontext, arrowFunc);

src/MoonSharp.Interpreter/Tree/Statements/ChunkStatement.cs

@@ -13,7 +13,8 @@ class ChunkStatement : Statement, IClosureBuilder
 		public ChunkStatement(ScriptLoadingContext lcontext)
 			: base(lcontext)
 		{
-			lcontext.Scope.PushFunction(this, true);
+			lcontext.Scope.PushFunction(this);
+			lcontext.Scope.SetHasVarArgs();
 			m_Env = lcontext.Scope.DefineLocal(WellKnownSymbols.ENV);
 			m_VarArgs = lcontext.Scope.DefineLocal(WellKnownSymbols.VARARGS);
 

src/MoonSharp.Tests/EndToEnd/CLike/SyntaxCLike/Functions/14-call-default-scope-arrow-arrow-default-flaky.lua renamed to src/MoonSharp.Tests/EndToEnd/CLike/SyntaxCLike/Functions/14-call-default-scope-arrow-arrow-default.lua

@@ -0,0 +1,21 @@
+local z = 2
+
+f = (x = () => {print(z)}) => {
+    x()
+}
+
+z = 3
+
+f();
+
+function test2() {
+    local z = 2
+    f = (x = () => {print(z)}) => {
+        x()
+    }
+    z = 7;
+    return f;
+}
+
+local f2 = test2();
+f2();

src/MoonSharp.Tests/EndToEnd/CLike/SyntaxCLike/Functions/14-call-default-scope-arrow-arrow-default-flaky.txt renamed to src/MoonSharp.Tests/EndToEnd/CLike/SyntaxCLike/Functions/14-call-default-scope-arrow-arrow-default.txt

@@ -0,0 +1,2 @@
+3
+7

src/MoonSharp.Tests/EndToEnd/CLike/SyntaxCLike/Functions/16-default-call-closure.lua

@@ -183,6 +183,16 @@ public void CFor_Closure()
             ", s => s.Options.Syntax = ScriptSyntax.CLike);
         }
 
+        [Test]
+        public void CallDefaultFunc()
+        {
+            TestScript.Run(@"
+            f = (x = () => {print('yes')}) => {
+                    x()
+            }
+            f();", s => s.Options.Syntax = ScriptSyntax.CLike);
+        }
+
         [Test]
         public void AddConcat()
         {