From a9f4ef1b65e2ae81527d15ed16f712e3b42708a4 Mon Sep 17 00:00:00 2001
From: Deukhoofd <Deukhoofd@gmail.com>
Date: Sun, 2 Dec 2018 17:26:23 +0100
Subject: [PATCH] Bind whether a variable symbol is a creation statement or
 just changing the variable

---
 Upsilon/Binder/Binder.cs              | 32 +++++++++++++++------------
 Upsilon/Binder/BoundVariableSymbol.cs |  4 +++-
 2 files changed, 21 insertions(+), 15 deletions(-)

diff --git a/Upsilon/Binder/Binder.cs b/Upsilon/Binder/Binder.cs
index ae97fb1..7ad3ca8 100644
--- a/Upsilon/Binder/Binder.cs
+++ b/Upsilon/Binder/Binder.cs
@@ -283,7 +283,7 @@ namespace Upsilon.Binder
                 _diagnostics.LogUnknownVariable(e.Identifier.Span, name);
                 return new BoundLiteralExpression(new ScriptNull(), e.Span);
             }
-            var boundVariable = new BoundVariableSymbol(variable, e.Identifier.Span);
+            var boundVariable = new BoundVariableSymbol(variable, false, e.Identifier.Span);
             return new BoundVariableExpression(boundVariable, e.Span);
         }
 
@@ -293,10 +293,11 @@ namespace Upsilon.Binder
             return new BoundExpressionStatement(exp, s.Span);
         }
 
-        private VariableSymbol TryBindVariable(string name, bool isLocal, BoundExpression assignment, string[] commentData)
+        private (VariableSymbol Symbol, bool IsCreation) TryBindVariable(string name, bool isLocal, BoundExpression assignment, string[] commentData)
         {
             if (name == "_")
-                return null;
+                return (null, false);
+            var isCreation = false;
             if (!Scope.TryGetVariable(name, !isLocal, out var variable))
             {
                 if (assignment.Type == Type.Table)
@@ -323,6 +324,8 @@ namespace Upsilon.Binder
                     Scope.DefineLocalVariable(variable);
                 else
                     Scope.AssignToNearest(variable);
+
+                isCreation = true;
             }
             else
             {
@@ -347,11 +350,11 @@ namespace Upsilon.Binder
                     else
                     {
                         _diagnostics.LogCannotConvert(assignment.Type, variable.Type, assignment.Span);
-                        return null;
+                        return (null, false);
                     }
                 }
             }
-            return variable;
+            return (variable, isCreation);
         }
 
         private BoundStatement BindAssignmentStatement(AssignmentStatementSyntax e)
@@ -363,14 +366,15 @@ namespace Upsilon.Binder
                 var boundExpression = BindExpression(e.Expression);
 
                 var isLocal = e.LocalToken != null;
-                var boundVariable = TryBindVariable(name, isLocal, boundExpression, e.CommentData);
-                if (boundVariable != null)
+                var (symbol, isCreation) = TryBindVariable(name, isLocal, boundExpression, e.CommentData);
+                if (symbol != null)
                 {
-                    if (boundVariable.Type == Type.Unknown)
+                    if (symbol.Type == Type.Unknown)
                     {
-                        _diagnostics.LogUnknownVariableType(boundVariable.Name, variableExpression.Span);
+                        _diagnostics.LogUnknownVariableType(symbol.Name, variableExpression.Span);
                     }
-                    var variable = new BoundVariableSymbol(boundVariable, variableExpression.Span);
+
+                    var variable = new BoundVariableSymbol(symbol, isCreation, variableExpression.Span);
                     return new BoundVariableAssignment(variable, boundExpression, isLocal, e.Span);
                 }
             }
@@ -387,11 +391,11 @@ namespace Upsilon.Binder
             foreach (var identifierToken in s.Identifiers)
             {
                 var boundVariable = TryBindVariable(identifierToken.Name, isLocal, assignment, null);
-                if (boundVariable.Type == Type.Unknown)
+                if (boundVariable.Symbol.Type == Type.Unknown)
                 {
-                    _diagnostics.LogUnknownVariableType(boundVariable.Name, identifierToken.Span);
+                    _diagnostics.LogUnknownVariableType(boundVariable.Symbol.Name, identifierToken.Span);
                 }
-                ls.Add(boundVariable);
+                ls.Add(boundVariable.Symbol);
             }
             return new BoundMultiAssignmentStatement(ls.ToImmutableArray(), assignment, s.Span);
         }
@@ -461,7 +465,7 @@ namespace Upsilon.Binder
                 {
                     variableSymbol = new FunctionParameterSymbol(variable.IdentifierName.Name, Type.Unknown);
                 }
-                parameters.Add(new BoundVariableSymbol(variableSymbol, identifierToken.Span));
+                parameters.Add(new BoundVariableSymbol(variableSymbol, true, identifierToken.Span));
                 innerScope.DefineLocalVariable(variableSymbol);
             }
 
diff --git a/Upsilon/Binder/BoundVariableSymbol.cs b/Upsilon/Binder/BoundVariableSymbol.cs
index 32b0bde..7bda29d 100644
--- a/Upsilon/Binder/BoundVariableSymbol.cs
+++ b/Upsilon/Binder/BoundVariableSymbol.cs
@@ -7,13 +7,15 @@ namespace Upsilon.Binder
 {
     public class BoundVariableSymbol : BoundExpression
     {
-        public BoundVariableSymbol(VariableSymbol variableSymbol, TextSpan span) : base(span)
+        public BoundVariableSymbol(VariableSymbol variableSymbol, bool isCreation, TextSpan span) : base(span)
         {
             VariableSymbol = variableSymbol;
+            IsCreation = isCreation;
         }
 
         public VariableSymbol VariableSymbol { get; }
 
+        public bool IsCreation { get; }
         public override BoundKind Kind => BoundKind.BoundVariableSymbol;
         public override IEnumerable<BoundNode> GetNodeAtPosition(int characterPosition)
         {