Resolve function parameter types by checking calls to the function

Upsilon/Binder/Binder.cs

@@ -13,6 +13,9 @@ namespace Upsilon.Binder
         private readonly Diagnostics _diagnostics;
         private BoundScope _scope;
 
+        private Dictionary<FunctionVariableSymbol, UnboundFunctionStatement> _unboundFunctions =
+            new Dictionary<FunctionVariableSymbol, UnboundFunctionStatement>();
+
         public Binder(Diagnostics diagnostics)
         {
             _diagnostics = diagnostics;
@@ -144,13 +147,22 @@ namespace Upsilon.Binder
                 parameters.Add(bound);
             }
 
-            for (var index = 0; index < function.Parameters.Length; index++)
+            if (!function.IsBound)
             {
-                var parameter = function.Parameters[index];
+                _scope = new BoundScope(_scope);
-                if (parameter.Type == Type.Unknown)
+                for (var index = 0; index < function.Parameters.Length; index++)
                 {
-                    parameter.Type = parameters[index].Type;
+                    var functionVariable = function.Parameters[index];
+                    var callingVariable = parameters[index];
+                    functionVariable.Type = callingVariable.Type;
+                    _scope.SetVariable(functionVariable);
                 }
+
+                _unboundFunctions[function].Block =
+                    (BoundBlockStatement) BindBlockStatement(_unboundFunctions[function].UnboundBlock);
+                _scope = _scope.ParentScope;
+                function.IsBound = true;
+                _unboundFunctions.Remove(function);
             }
 
             //TODO: validate parameters
@@ -297,10 +309,20 @@ namespace Upsilon.Binder
                 }
             }
 
-            _scope = innerScope;
+            if (parameters.Count == 0)
-            var block = BindBlockStatement(e.Block);
+            {
-            _scope = _scope.ParentScope;
+                _scope = innerScope;
-            return new BoundFunctionStatement(variable, parameters.ToImmutable(), (BoundBlockStatement) block);
+                var block = BindBlockStatement(e.Block);
+                _scope = _scope.ParentScope;
+                ((FunctionVariableSymbol) variable).IsBound = true;
+                return new BoundFunctionStatement(variable, parameters.ToImmutable(), (BoundBlockStatement) block);
+            }
+            else
+            {
+                var unbound = new UnboundFunctionStatement(variable, parameters.ToImmutable(), e.Block);
+                _unboundFunctions.Add((FunctionVariableSymbol) variable, unbound);
+                return unbound;
+            }
         }
 
     }

Upsilon/Binder/BoundKind.cs

@@ -17,5 +17,6 @@ namespace Upsilon.Binder
         BoundIfStatement,
         BoundElseStatement,
         BoundFunctionStatement,
+        BoundPromise
     }
 }

Upsilon/Binder/BoundStatements/UnboundFunctionStatement.cs

@@ -0,0 +1,23 @@
+using System.Collections.Immutable;
+using Upsilon.Parser;
+
+namespace Upsilon.Binder
+{
+    public class UnboundFunctionStatement : BoundStatement
+    {
+        public UnboundFunctionStatement(VariableSymbol identifier, ImmutableArray<VariableSymbol> parameters,
+            BlockStatementSyntax unboundBlock)
+        {
+            Identifier = identifier;
+            Parameters = parameters;
+            UnboundBlock = unboundBlock;
+        }
+
+        public override BoundKind Kind => BoundKind.BoundPromise;
+
+        public VariableSymbol                 Identifier { get; }
+        public ImmutableArray<VariableSymbol> Parameters { get; }
+        public BlockStatementSyntax UnboundBlock { get; }
+        public BoundBlockStatement Block { get; set; }
+    }
+}

Upsilon/Binder/UnboundFunction.cs

@@ -1,7 +0,0 @@
-namespace Upsilon.Binder
-{
-    public class UnboundFunction
-    {
-
-    }
-}

Upsilon/Binder/VariableSymbol.cs

@@ -20,6 +20,7 @@ namespace Upsilon.Binder
     public class FunctionVariableSymbol : VariableSymbol
     {
         public ImmutableArray<VariableSymbol> Parameters { get; }
+        public bool IsBound { get; set; }
 
         public FunctionVariableSymbol(string name, Type type, bool local, ImmutableArray<VariableSymbol> parameters)
             : base(name, type, local)

Upsilon/Evaluator/Evaluator.cs

@@ -40,6 +40,9 @@ namespace Upsilon.Evaluator
                 case BoundKind.BoundFunctionStatement:
                     EvaluateBoundFunctionStatement((BoundFunctionStatement) e);
                     break;
+                case BoundKind.BoundPromise:
+                    EvaluateUnboundFunctionStatement((UnboundFunctionStatement) e);
+                    break;
                 default:
                     EvaluateExpressionStatement((BoundExpressionStatement) e);
                     break;
@@ -170,6 +173,16 @@ namespace Upsilon.Evaluator
                 Scope.SetGlobal(boundFunctionStatement.Identifier, func);
         }
 
+        private void EvaluateUnboundFunctionStatement(UnboundFunctionStatement unboundFunctionStatement)
+        {
+            var func = new LuaFunction(unboundFunctionStatement.Parameters, unboundFunctionStatement.Block);
+            if (unboundFunctionStatement.Identifier.Local)
+                Scope.Set(unboundFunctionStatement.Identifier, func);
+            else
+                Scope.SetGlobal(unboundFunctionStatement.Identifier, func);
+
+        }
+
         private LuaType EvaluateBoundFunctionCallExpression(BoundFunctionCallExpression boundFunctionCallExpression)
         {
             var name = boundFunctionCallExpression.Identifier;
@@ -191,5 +204,7 @@ namespace Upsilon.Evaluator
             Scope = Scope.ParentScope;
             return _value;
         }
+
+
     }
 }

UpsilonTests/FunctionTests.cs

@@ -52,17 +52,34 @@ testFunc(100)
         {
             const string input = @"
 function testFunc (var1)
-    b = var1 == true
+    var1 == true
 end
 testFunc(100)
 ";
             var script = new Script(input);
             Assert.Empty(script.Diagnostics.Messages);
             script.Evaluate();
-            Assert.Empty(script.Diagnostics.Messages);
+            Assert.Single(script.Diagnostics.Messages);
             Assert.True(script.Scope.TryGet("testFunc", out var func));
             Assert.IsType<LuaFunction>(func);
         }
 
+        [Fact]
+        public void BindUnusedFunctions()
+        {
+            const string input = @"
+function testFunc (var1)
+    var1 == true
+end
+";
+            var script = new Script(input);
+            Assert.Empty(script.Diagnostics.Messages);
+            script.Evaluate();
+            Assert.Empty(script.Diagnostics.Messages);
+            Assert.True(script.Scope.TryGet("testFunc", out var func));
+            var castType = Assert.IsType<LuaFunction>(func);
+            Assert.NotNull(castType.Block);
+        }
+
     }
 }