Wire up resolver to interpreter

Interpreter.cs

@@ -64,6 +64,20 @@ public class Env
 			}
 		}
 	}
+
+	public Env Ancestor(int distance)
+	{
+		Env? curr = this;
+		for (int i = 0; i < distance; i++)
+		{
+			curr = curr.enclosing;
+			if (curr is null)
+			{
+				throw new IndexOutOfRangeException();
+			}
+		}
+		return curr;
+	}
 }
 
 public interface Callable
@@ -302,14 +316,16 @@ public class Interpreter : AST.IExprVisitor<Env, object>
 				binding.Params[i].accept((arguments[i], env), new PatternBinder());
 			}
 			return interpreter.evaluate(env, binding.Value);
-			// throw new NotImplementedException();
 		}
 	}
 
 	protected internal readonly Env Globals = new Env();
+	private readonly Resolver Resolver;
 
-	public Interpreter()
+	public Interpreter(Resolver resolver)
 	{
+		Resolver = resolver;
+
 		Globals["clock"] = new NativeFunction((args) =>
 		{
 			return (double)DateTimeOffset.Now.ToUnixTimeSeconds();
@@ -413,14 +429,14 @@ public class Interpreter : AST.IExprVisitor<Env, object>
 			case TokenType.BangEqual:
 				return Variant.FromBool((left, right) switch
 				{
-					(String l, String r) => l != r,
+					(string l, string r) => l != r,
 					(double l, double r) => l != r,
 					_ => throw new ArgumentException(),
 				});
 			case TokenType.DoubleEqual:
 				return Variant.FromBool((left, right) switch
 				{
-					(String l, String r) => l == r,
+					(string l, string r) => l == r,
 					(double l, double r) => l == r,
 					_ => throw new ArgumentException(),
 				});
@@ -453,7 +469,15 @@ public class Interpreter : AST.IExprVisitor<Env, object>
 
 	public object visitVariableExpr(Env env, AST.Variable expr)
 	{
-		return env[expr.Value];
+		var name = (string)expr.Value.Literal!;
+		if (Resolver.TryResolve(expr, out var distance))
+		{
+			return env.Ancestor(distance)[expr.Value];
+		}
+		else
+		{
+			return Globals[expr.Value];
+		}
 	}
 
 	public object visitIfExpr(Env env, AST.If expr)
@@ -499,9 +523,11 @@ public class Interpreter : AST.IExprVisitor<Env, object>
 					}
 					catch (Exception e)
 					{
-						var start = e is PatternMismatchException ?
+						var start = e switch
-							((PatternMismatchException)e).Start :
+						{
-							binding.Start;
+							PatternMismatchException pme => pme.Start,
+							_ => binding.Start,
+						};
 						throw new RuntimeError(start, e.Message);
 					}
 					break;

Program.cs

@@ -7,7 +7,8 @@ namespace Finn;
 
 class Program
 {
-	private static readonly Interpreter interpreter = new Interpreter();
+	private static readonly Resolver resolver = new Resolver();
+	private static readonly Interpreter interpreter = new Interpreter(resolver);
 	static bool hadError = false;
 	static bool hadRuntimeError = true;
 
@@ -41,16 +42,8 @@ class Program
 	{
 		var scanner = new Scanner(src);
 		List<Token> tokens = scanner.scanTokens();
-		// Console.WriteLine("TOKENS\n=======");
-		// foreach (var token in tokens)
-		// {
-		// 	Console.WriteLine(token);
-		// }
 		Parser parser = new Parser(tokens);
 		Expr? expression = parser.parse();
-		// Console.WriteLine("\nAST\n=======");
-		// Console.WriteLine(expression);
-		// Console.WriteLine();
 
 		if (hadError)
 		{
@@ -58,6 +51,13 @@ class Program
 			return;
 		}
 
+		resolver.Add(expression!);
+		if (hadError)
+		{
+			hadError = false;
+			return;
+		}
+
 		interpreter.Interpret(expression!);
 	}
 

Resolver.cs

@@ -8,8 +8,24 @@ using ScopeStack = System.Collections.Immutable.ImmutableStack<System.Collection
 using Resolutions = System.Collections.Immutable.ImmutableDictionary<Finn.AST.Expr, int>;
 using System.Collections.Generic;
 
-class Resolver : IExprVisitor<ScopeStack, Resolutions>
+public class Resolver
 {
+	private static readonly Resolutions EmptyResolutions = Resolutions.Empty.WithComparers(ReferenceEqualityComparer.Instance);
+
+	private Resolutions Resolutions = EmptyResolutions;
+	public bool TryResolve(Expr expr, out int distance)
+	{
+		return Resolutions.TryGetValue(expr, out distance);
+	}
+
+	public void Add(Expr expr)
+	{
+		var newResolutions = ResolverBuilder.Instance.Resolve(ScopeStack.Empty, expr);
+		Resolutions = Resolutions.AddRange(newResolutions);
+	}
+
+	private class ResolverBuilder : IExprVisitor<ScopeStack, Resolutions>
+	{
 		private class NameCollection
 		{
 			public ImmutableHashSet<string> Names { get; private set; } = ImmutableHashSet<string>.Empty;
@@ -74,14 +90,13 @@ class Resolver : IExprVisitor<ScopeStack, Resolutions>
 			}
 		}
 
-	private static readonly Resolutions EmptyResolutions = Resolutions.Empty.WithComparers(ReferenceEqualityComparer.Instance);
+		public static readonly ResolverBuilder Instance = new ResolverBuilder();
-	public static readonly Resolver Instance = new Resolver();
 
-	private Resolver() { }
+		private ResolverBuilder() { }
 
 		private static Resolutions AddRange(Resolutions r1, Resolutions r2) => r1.AddRange(r2);
 
-	private Resolutions Resolve(ScopeStack scopes, Expr expr)
+		public Resolutions Resolve(ScopeStack scopes, Expr expr)
 		{
 			return expr.accept(scopes, this);
 		}
@@ -254,4 +269,6 @@ class Resolver : IExprVisitor<ScopeStack, Resolutions>
 				return Resolve(scopes, names.Names, _case.Value);
 			}
 		}
+	}
 }
+

TODO.txt

@@ -1,4 +1,3 @@
-Wire up resolver to interpreter
 Move let-expr resolvability check to Resolver
 Remove dynamic type checks (checkXXX methods) from interpreter
 Use numerical indices in resolutions