Handle if statements

Upsilon/Binder/Binder.cs

@@ -33,6 +33,8 @@ namespace Upsilon.Binder
                     return BindAssignmentStatement((AssignmentExpressionSyntax) s);
                 case SyntaxKind.BlockStatement:
                     return BindBlockStatement((BlockStatementSyntax) s);
+                case SyntaxKind.IfStatement:
+                    return BindIfStatement((IfStatementSyntax) s);
             }
 
             throw new NotImplementedException(s.Kind.ToString());
@@ -173,5 +175,13 @@ namespace Upsilon.Binder
             }
             return new BoundBlockStatement(arr.ToImmutable());
         }
+
+        private BoundStatement BindIfStatement(IfStatementSyntax e)
+        {
+            var condition = BindExpressionStatement(e.Condition);
+            var block = BindBlockStatement(e.Block);
+            return new BoundIfStatement((BoundExpressionStatement) condition, (BoundBlockStatement) block);
+        }
+
     }
 }

Upsilon/Binder/BoundIfStatement.cs

@@ -0,0 +1,16 @@
+namespace Upsilon.Binder
+{
+    public class BoundIfStatement : BoundStatement
+    {
+        public BoundIfStatement(BoundExpressionStatement condition, BoundBlockStatement block)
+        {
+            Condition = condition;
+            Block = block;
+        }
+
+        public override BoundKind Kind => BoundKind.BoundIfStatement;
+
+        public BoundExpressionStatement Condition { get; }
+        public BoundBlockStatement Block { get; }
+    }
+}

Upsilon/Binder/BoundKind.cs

@@ -12,6 +12,7 @@ namespace Upsilon.Binder
         // Statements
         BoundAssignmentStatement,
         BoundExpressionStatement,
-        BoundBlockStatement
+        BoundBlockStatement,
+        BoundIfStatement
     }
 }

Upsilon/Diagnostics.cs

@@ -25,9 +25,9 @@ namespace Upsilon
             Log(DiagnosticLevel.Error, message, location);
         }
 
-        public void LogBadCharacter(TextSpan location)
+        public void LogBadCharacter(TextSpan location, SyntaxKind expectedToken)
         {
-            LogError($"Invalid character found", location);
+            LogError($"Invalid character found. Expected: '{expectedToken}'", location);
         }
 
         public void LogUnknownVariable(TextSpan span, string variable)

Upsilon/Evaluator/Evaluator.cs

@@ -40,6 +40,9 @@ namespace Upsilon.Evaluator
                 case BoundKind.BoundBlockStatement:
                     EvaluateBoundBlockStatement((BoundBlockStatement) e);
                     break;
+                case BoundKind.BoundIfStatement:
+                    EvaluateBoundIfStatement((BoundIfStatement) e);
+                    break;
                 default:
                     EvaluateExpressionStatement((BoundExpressionStatement) e);
                     break;
@@ -127,5 +130,14 @@ namespace Upsilon.Evaluator
                 EvaluateStatement(boundStatement);
             }
         }
+
+        private void EvaluateBoundIfStatement(BoundIfStatement boundBlockStatement)
+        {
+            var condition = EvaluateExpression(boundBlockStatement.Condition.Expression);
+            if ((bool) condition)
+            {
+                EvaluateBoundBlockStatement(boundBlockStatement.Block);
+            }
+        }
     }
 }

Upsilon/Evaluator/Script.cs

@@ -18,6 +18,8 @@ namespace Upsilon.Evaluator
             ScriptString = new SourceText(scriptString);
             Diagnostics = new Diagnostics(ScriptString);
             _parsed = Parser.Parser.Parse(scriptString, Diagnostics);
+            if (variables == null)
+                variables = new Dictionary<VariableSymbol, object>();
             Binder = new Binder.Binder(new BoundScope(variables, null), Diagnostics);
             Evaluator = new Evaluator(this, Diagnostics, variables);
         }

Upsilon/Parser/Lexer.cs

@@ -99,7 +99,7 @@ namespace Upsilon.Parser
                 default:
                     if (char.IsLetter(Current))
                         return LexIdentifierOrKeyword();
-                    _diagnostics.LogBadCharacter(new TextSpan(_position, 1));
+                    _diagnostics.LogBadCharacter(new TextSpan(_position, 1), SyntaxKind.Identifier);
                     return new SyntaxToken(SyntaxKind.BadToken, _position, "", null);
             }
         }
@@ -116,7 +116,7 @@ namespace Upsilon.Parser
                 {
                     if (hasDecimalPoint)
                     {
-                        _diagnostics.LogBadCharacter(new TextSpan(_position, 1));
+                        _diagnostics.LogBadCharacter(new TextSpan(_position, 1), SyntaxKind.Number);
                         return new SyntaxToken(SyntaxKind.BadToken, _position, "", null);
                     }
                     hasDecimalPoint = true;

Upsilon/Parser/Parser.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Immutable;
 using Upsilon.Text;
 
@@ -43,13 +44,14 @@ namespace Upsilon.Parser
             if (Current.Kind == kind)
                 return NextToken();
 
-            _diagnostics.LogBadCharacter(Current.Span);
+            _diagnostics.LogBadCharacter(Current.Span, kind);
             return new SyntaxToken(kind, Current.Span.Start, "", null);
         }
 
         public StatementSyntax ParseScriptSyntax()
         {
             var statement = ParseBlockStatement();
+            MatchToken(SyntaxKind.EndOfFile);
             return statement;
         }
 
@@ -63,6 +65,10 @@ namespace Upsilon.Parser
             {
                 return ParseAssignmentExpression();
             }
+            if (Current.Kind == SyntaxKind.IfKeyword)
+            {
+                return ParseIfStatement();
+            }
 
             return ParseExpressionStatement();
         }
@@ -75,8 +81,17 @@ namespace Upsilon.Parser
                 var next = ParseStatement();
                 statements.Add(next);
             }
-            var endToken = NextToken();
-            return new BlockStatementSyntax(statements.ToImmutable(), endToken);
+            return new BlockStatementSyntax(statements.ToImmutable());
+        }
+
+        public StatementSyntax ParseIfStatement()
+        {
+            var ifToken = MatchToken(SyntaxKind.IfKeyword);
+            var condition = ParseExpressionStatement();
+            var thenToken = MatchToken(SyntaxKind.ThenKeyword);
+            var block = ParseBlockStatement();
+            var endToken = MatchToken(SyntaxKind.EndKeyword);
+            return new IfStatementSyntax(ifToken, condition, thenToken, (BlockStatementSyntax) block, endToken);
         }
 
         public ExpressionStatementSyntax ParseExpressionStatement()
@@ -147,7 +162,7 @@ namespace Upsilon.Parser
                     var token = MatchToken(SyntaxKind.Identifier);
                     return new VariableExpressionSyntax((IdentifierToken) token);
                 default:
-                    _diagnostics.LogBadCharacter(new TextSpan(_position, 1));
+                    _diagnostics.LogBadCharacter(new TextSpan(_position, 1), SyntaxKind.Identifier);
                     NextToken();
                     return new BadExpressionSyntax();
             }

Upsilon/Parser/StatementSyntax/BlockStatementSyntax.cs

@@ -7,17 +7,16 @@ namespace Upsilon.Parser
 {
     public sealed class BlockStatementSyntax : StatementSyntax
     {
-        public BlockStatementSyntax(ImmutableArray<StatementSyntax> statements, SyntaxToken endToken)
+        public BlockStatementSyntax(ImmutableArray<StatementSyntax> statements)
         {
             Statements = statements;
-            EndToken = endToken;
             var first = statements.FirstOrDefault();
-            if (first != null)
-                Span = new TextSpan(first.Span.Start, endToken.Span.End);
+            var last = statements.LastOrDefault();
+            if (first != null && last != null)
+                Span = new TextSpan(first.Span.Start, last.Span.End);
         }
 
         public ImmutableArray<StatementSyntax> Statements { get; }
-        public SyntaxToken EndToken { get; }
         public override SyntaxKind Kind => SyntaxKind.BlockStatement;
         public override IEnumerable<SyntaxNode> ChildNodes()
         {

Upsilon/Parser/StatementSyntax/IfStatementSyntax.cs

@@ -0,0 +1,37 @@
+using System.Collections.Generic;
+using Upsilon.Text;
+
+namespace Upsilon.Parser
+{
+    public sealed class IfStatementSyntax : StatementSyntax
+    {
+        public IfStatementSyntax(SyntaxToken ifToken, ExpressionStatementSyntax condition, SyntaxToken thenToken,
+            BlockStatementSyntax block, SyntaxToken endToken)
+        {
+            IfToken = ifToken;
+            Condition = condition;
+            ThenToken = thenToken;
+            Block = block;
+            EndToken = endToken;
+
+            Span = new TextSpan(ifToken.Span.Start, endToken.Span.End);
+        }
+
+
+        public SyntaxToken IfToken { get; }
+        public ExpressionStatementSyntax Condition { get; }
+        public SyntaxToken ThenToken { get; }
+        public BlockStatementSyntax Block { get; }
+        public SyntaxToken EndToken { get; }
+
+        public override SyntaxKind Kind => SyntaxKind.IfStatement;
+        public override IEnumerable<SyntaxNode> ChildNodes()
+        {
+            yield return IfToken;
+            yield return Condition;
+            yield return ThenToken;
+            yield return Block;
+            yield return EndToken;
+        }
+    }
+}

Upsilon/Parser/SyntaxKeyWords.cs

@@ -20,6 +20,10 @@ namespace Upsilon.Parser
                     return SyntaxKind.LocalKeyword;
                 case "end":
                     return SyntaxKind.EndKeyword;
+                case "if":
+                    return SyntaxKind.IfKeyword;
+                case "then":
+                    return SyntaxKind.ThenKeyword;
                 default:
                     return SyntaxKind.Identifier;
             }

Upsilon/Parser/SyntaxKind.cs

@@ -28,6 +28,8 @@ namespace Upsilon.Parser
         OrKeyword,
         LocalKeyword,
         EndKeyword,
+        IfKeyword,
+        ThenKeyword,
 
         Identifier,
 
@@ -45,6 +47,7 @@ namespace Upsilon.Parser
 
         // statements
         ExpressionStatement,
-        BlockStatement
+        BlockStatement,
+        IfStatement
     }
 }

Upsilon/Upsilon.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
     <PropertyGroup>
         <TargetFramework>netstandard2.0</TargetFramework>

UpsilonTests/IfTests.cs

@@ -0,0 +1,18 @@
+using Upsilon.Evaluator;
+using Xunit;
+
+namespace UpsilonTests
+{
+    public class IfTests
+    {
+        [Fact]
+        public void BasicIfTest()
+        {
+            var input = "if true then val = true end";
+            var script = new Script(input);
+            Assert.Empty(script.Diagnostics.Messages);
+            var actual = script.Evaluate<bool>();
+            Assert.True(actual);
+        }
+    }
+}

Yc/Program.cs

@@ -47,8 +47,9 @@ namespace Yc
                 }
                 else
                 {
+                    Console.ForegroundColor = ConsoleColor.Cyan;
                     Console.WriteLine(evaluate);
-                    //variables = parsed.Variables;
+                    Console.ResetColor();
                 }
             }
         }