diff --git a/AST.cs b/AST.cs
index de46020..41efef7 100644
--- a/AST.cs
+++ b/AST.cs
@@ -1,7 +1,40 @@
+using System.CodeDom.Compiler;
+
 namespace Finn.AST;
 
-public record Name(string Value, bool Quoted);
+public record Name(string Value, bool Quoted)
+{
+	public override string ToString()
+	{
+		if (this.Quoted) return $"@\"{this.Value}\"";
+		return this.Value;
+	}
+};
 
 public record Field(Name Name, Expr? Value);
 
 public record BaseRecord(Expr Value, Field[] Updates);
+
+public partial record Identifier
+{
+	public override string ToString()
+	{
+		return this.Value.ToString();
+	}
+}
+
+public partial record Binary
+{
+	public override string ToString()
+	{
+		return $"Binary {{ Left = {this.Left}, Op = {this.Op.lexeme}, Right = {this.Right} }}";
+	}
+}
+
+public partial record Literal
+{
+	public override string ToString()
+	{
+		return this.Value.ToString()!;
+	}
+}
diff --git a/ASTPrinter.cs b/ASTPrinter.cs
deleted file mode 100644
index 4e7ffdd..0000000
--- a/ASTPrinter.cs
+++ /dev/null
@@ -1,153 +0,0 @@
-using System;
-using System.IO;
-using Finn.AST;
-
-namespace Finn;
-
-class ASTPrinter : IVisitor<string>
-{
-	public string print(Expr expr)
-	{
-		return expr.accept(this);
-	}
-
-	private string parenthesize(string name, params Expr[] exprs)
-	{
-		var w = new StringWriter();
-		w.Write($"({name}");
-		foreach (Expr expr in exprs)
-		{
-			w.Write(" ");
-			w.Write(expr.accept(this));
-		}
-		w.Write(")");
-		return w.ToString();
-	}
-
-	public string visitBinaryExpr(Binary expr)
-	{
-		return parenthesize(expr.Op.lexeme, expr.Left, expr.Right);
-	}
-
-	public string visitGroupingExpr(Grouping expr)
-	{
-		return parenthesize("group", expr.Expression);
-	}
-
-	public string visitLiteralExpr(Literal expr)
-	{
-		return expr.Value.ToString() ?? "";
-	}
-
-	private string formatName(Name name)
-	{
-		if (name.Quoted) return $"@\"{name.Value}\"";
-		return name.Value;
-	}
-
-	public string visitIdentifierExpr(Identifier expr)
-	{
-		return formatName(expr.Value);
-	}
-
-	public string visitUnaryExpr(Unary expr)
-	{
-		return parenthesize(expr.Op.lexeme, expr.Right);
-	}
-
-	public string visitIfExpr(If expr)
-	{
-		return parenthesize("if", expr.Condition, expr.Then, expr.Else);
-	}
-
-	public string visitSequenceExpr(Sequence expr)
-	{
-		return parenthesize("seq", expr.Left, expr.Right);
-	}
-
-	public string visitSelectorExpr(Selector expr)
-	{
-		return parenthesize(".", expr.Left, new Identifier { Value = expr.FieldName });
-	}
-
-	public string visitListExpr(List expr)
-	{
-		return parenthesize("list", expr.Elements);
-	}
-
-	public string visitVariantExpr(Variant expr)
-	{
-		if (expr.Argument == null)
-		{
-			return parenthesize("variant", new Identifier { Value = expr.Tag });
-		}
-		return parenthesize("variant", new Identifier { Value = expr.Tag }, expr.Argument);
-	}
-
-	public string visitRecordExpr(Record expr)
-	{
-		StringWriter w = new StringWriter();
-		w.Write("(record");
-
-		writeFields("extend", expr.Extensions);
-
-		if (expr.Base != null)
-		{
-			w.Write(" (base ");
-			w.Write(print(expr.Base.Value));
-			writeFields("update", expr.Base.Updates);
-			w.Write(')');
-		}
-		w.Write(')');
-
-		return w.ToString();
-
-		void writeFields(string header, Field[] fields)
-		{
-			if (fields.Length != 0)
-			{
-				w.Write($" ({header}");
-				foreach (var field in fields)
-				{
-					w.Write(' ');
-					var name = formatName(field.Name);
-					if (field.Value == null)
-					{
-						w.Write(name);
-					}
-					else
-					{
-						w.Write(parenthesize(name, field.Value));
-					}
-				}
-				w.Write(')');
-			}
-
-		}
-	}
-
-	public string visitIndexerExpr(Indexer expr)
-	{
-		return parenthesize("index", expr.Left, expr.Index);
-	}
-
-	public string visitCallExpr(Call expr)
-	{
-		var w = new StringWriter();
-		w.Write("(call ");
-		w.Write(print(expr.Left));
-		foreach (var arg in expr.Arguments)
-		{
-			if (arg == null)
-			{
-				w.Write(" _");
-			}
-			else
-			{
-				w.Write($" {print(arg)}");
-			}
-		}
-		w.Write(')');
-		return w.ToString();
-	}
-}
diff --git a/Expr.g.cs b/Expr.g.cs
index b2c5169..d517e1a 100644
--- a/Expr.g.cs
+++ b/Expr.g.cs
@@ -7,7 +7,7 @@
 
 namespace Finn.AST;
 
-public abstract class Expr {
+public abstract record Expr() {
 	public abstract T accept<T>(IVisitor<T> visitor);
 }
 public interface IVisitor<T> {
@@ -25,116 +25,92 @@ public interface IVisitor<T> {
 	T visitIndexerExpr(Indexer expr);
 	T visitCallExpr(Call expr);
 }
-public class Sequence : Expr
+public partial record Sequence(Expr Left, Expr Right) : Expr()
 {
-	public required Expr Left { get; init; }
-	public required Expr Right { get; init; }
 	public override T accept<T>(IVisitor<T> visitor)
 	{
 		return visitor.visitSequenceExpr(this);
 	}
 }
-public class Binary : Expr
+public partial record Binary(Expr Left, Token Op, Expr Right) : Expr()
 {
-	public required Expr Left { get; init; }
-	public required Token Op { get; init; }
-	public required Expr Right { get; init; }
 	public override T accept<T>(IVisitor<T> visitor)
 	{
 		return visitor.visitBinaryExpr(this);
 	}
 }
-public class Grouping : Expr
+public partial record Grouping(Expr Expression) : Expr()
 {
-	public required Expr Expression { get; init; }
 	public override T accept<T>(IVisitor<T> visitor)
 	{
 		return visitor.visitGroupingExpr(this);
 	}
 }
-public class Literal : Expr
+public partial record Literal(System.Object Value) : Expr()
 {
-	public required System.Object Value { get; init; }
 	public override T accept<T>(IVisitor<T> visitor)
 	{
 		return visitor.visitLiteralExpr(this);
 	}
 }
-public class Unary : Expr
+public partial record Unary(Token Op, Expr Right) : Expr()
 {
-	public required Token Op { get; init; }
-	public required Expr Right { get; init; }
 	public override T accept<T>(IVisitor<T> visitor)
 	{
 		return visitor.visitUnaryExpr(this);
 	}
 }
-public class If : Expr
+public partial record If(Expr Condition, Expr Then, Expr Else) : Expr()
 {
-	public required Expr Condition { get; init; }
-	public required Expr Then { get; init; }
-	public required Expr Else { get; init; }
 	public override T accept<T>(IVisitor<T> visitor)
 	{
 		return visitor.visitIfExpr(this);
 	}
 }
-public class Identifier : Expr
+public partial record Identifier(Name Value) : Expr()
 {
-	public required Name Value { get; init; }
 	public override T accept<T>(IVisitor<T> visitor)
 	{
 		return visitor.visitIdentifierExpr(this);
 	}
 }
-public class List : Expr
+public partial record List(Expr[] Elements) : Expr()
 {
-	public required Expr[] Elements { get; init; }
 	public override T accept<T>(IVisitor<T> visitor)
 	{
 		return visitor.visitListExpr(this);
 	}
 }
-public class Variant : Expr
+public partial record Variant(Name Tag, Expr? Argument) : Expr()
 {
-	public required Name Tag { get; init; }
-	public required Expr? Argument { get; init; }
 	public override T accept<T>(IVisitor<T> visitor)
 	{
 		return visitor.visitVariantExpr(this);
 	}
 }
-public class Record : Expr
+public partial record Record(Field[] Extensions, BaseRecord? Base) : Expr()
 {
-	public required Field[] Extensions { get; init; }
-	public required BaseRecord? Base { get; init; }
 	public override T accept<T>(IVisitor<T> visitor)
 	{
 		return visitor.visitRecordExpr(this);
 	}
 }
-public class Selector : Expr
+public partial record Selector(Expr Left, Name FieldName) : Expr()
 {
-	public required Expr Left { get; init; }
-	public required Name FieldName { get; init; }
 	public override T accept<T>(IVisitor<T> visitor)
 	{
 		return visitor.visitSelectorExpr(this);
 	}
 }
-public class Indexer : Expr
+public partial record Indexer(Expr Left, Expr Index) : Expr()
 {
-	public required Expr Left { get; init; }
-	public required Expr Index { get; init; }
 	public override T accept<T>(IVisitor<T> visitor)
 	{
 		return visitor.visitIndexerExpr(this);
 	}
 }
-public class Call : Expr
+public partial record Call(Expr Left, Expr?[] Arguments) : Expr()
 {
-	public required Expr Left { get; init; }
-	public required Expr?[] Arguments { get; init; }
 	public override T accept<T>(IVisitor<T> visitor)
 	{
 		return visitor.visitCallExpr(this);
diff --git a/Parser.cs b/Parser.cs
index a63ce43..20b4c84 100644
--- a/Parser.cs
+++ b/Parser.cs
@@ -119,7 +119,7 @@ class Parser
 		{
 			Token op = previous();
 			Expr right = next();
-			expr = new Binary { Left = expr, Op = op, Right = right };
+			expr = new Binary(expr, op, right);
 		}
 
 		return expr;
@@ -133,23 +133,13 @@ class Parser
 		while (match(TokenType.Semicolon))
 		{
 			var right = equality();
-			expr = new Sequence { Left = expr, Right = right };
+			expr = new Sequence(expr, right);
 		}
 		return expr;
 	}
 
-	private Expr equality()
-	{
-		Expr expr = comparison();
-
-		while (match(TokenType.BangEqual, TokenType.DoubleEqual))
-		{
-			Token op = previous();
-			Expr right = comparison();
-			expr = new Binary { Left = expr, Op = op, Right = right };
-		}
-		return expr;
-	}
+	private Expr equality() =>
+		binaryLeft(comparison, TokenType.BangEqual, TokenType.DoubleEqual);
 
 	private Expr comparison() =>
 		binaryLeft(sum, TokenType.Greater, TokenType.GreaterEqual, TokenType.Less, TokenType.LessEqual);
@@ -166,7 +156,7 @@ class Parser
 		{
 			Token op = previous();
 			Expr right = unary();
-			return new Unary { Op = op, Right = right };
+			return new Unary(op, right);
 		}
 		return control();
 	}
@@ -182,7 +172,7 @@ class Parser
 				Expr thenCase = expression();
 				consume(TokenType.Else, "Expect 'else' after 'then' case.");
 				Expr elseCase = expression();
-				return new If { Condition = condition, Then = thenCase, Else = elseCase };
+				return new If(condition, thenCase, elseCase);
 			case TokenType.When:
 				throw new NotImplementedException("TODO when");
 		}
@@ -215,14 +205,14 @@ class Parser
 			{
 				throw error(advance(), "Expect identifier after dot.");
 			}
-			return new Selector { Left = expr, FieldName = ident };
+			return new Selector(expr, ident);
 		}
 
 		if (match(TokenType.LBracket))
 		{
 			var index = expression();
 			consume(TokenType.RBracket, "Expect '[' after expression.");
-			return new Indexer { Left = expr, Index = index };
+			return new Indexer(expr, index);
 		}
 
 		if (match(TokenType.LParen))
@@ -244,7 +234,7 @@ class Parser
 				}
 			}
 			consume(TokenType.RParen, "Expect '(' after arguments.");
-			return new Call { Left = expr, Arguments = args.ToArray() };
+			return new Call(expr, args.ToArray());
 		}
 
 		return expr;
@@ -255,20 +245,20 @@ class Parser
 		if (match(TokenType.Number, TokenType.String))
 		{
 			object literal = previous().literal!;
-			return new Literal { Value = previous().literal! };
+			return new Literal(previous().literal!);
 		}
 
 		var ident = name();
 		if (ident != null)
 		{
-			return new Identifier { Value = ident };
+			return new Identifier(ident);
 		}
 
 		if (match(TokenType.LParen))
 		{
 			Expr groupedExpr = expression();
 			consume(TokenType.RParen, "Expect ')' after expression.");
-			return new Grouping { Expression = groupedExpr };
+			return new Grouping(groupedExpr);
 		}
 
 		Expr? expr;
@@ -319,7 +309,7 @@ class Parser
 				}
 			}
 		}
-		return new Finn.AST.List { Elements = elements.ToArray() };
+		return new Finn.AST.List(elements.ToArray());
 	}
 
 	private Expr? variant()
@@ -342,7 +332,7 @@ class Parser
 				consume(TokenType.RParen, "Expect ')' after variant argument.");
 			}
 		}
-		return new Variant { Tag = tag, Argument = argument };
+		return new Variant(tag, argument);
 	}
 
 	private Expr? record()
@@ -363,11 +353,7 @@ class Parser
 		}
 
 		consume(TokenType.RBrace, "Expect '}' at end of record literal.");
-		return new Record
-		{
-			Extensions = extensions,
-			Base = baseRecord,
-		};
+		return new Record(extensions, baseRecord);
 
 		Field[] parseFields(params TokenType[] endAt)
 		{
diff --git a/Program.cs b/Program.cs
index cb8be40..da2f8e1 100644
--- a/Program.cs
+++ b/Program.cs
@@ -45,7 +45,7 @@ class Program
 			return;
 		}
 
-		Console.WriteLine(new ASTPrinter().print(expression));
+		Console.WriteLine(expression);
 	}
 
 	static void runPrompt()
diff --git a/ast_classes.fsx b/ast_classes.fsx
index abe7d3d..e19018a 100644
--- a/ast_classes.fsx
+++ b/ast_classes.fsx
@@ -51,13 +51,13 @@ let renderIVisitor (sw: System.IO.StreamWriter) (baseName: string) types =
     sw.Write("}\n")
 
 let renderType (sw: System.IO.StreamWriter) baseName t =
-    sw.Write
-        $"public class {t.Name} : {baseName}
+    let writeField i field =
+      if i > 0 then sw.Write(", ")
+      sw.Write $"{field.Type} {field.Name}"
+    sw.Write $"public partial record {t.Name}("
+    List.iteri writeField t.Fields
+    sw.Write $") : {baseName}()
 {{\n"
-
-    for f in t.Fields do
-        sw.Write $"\tpublic required {f.Type} {f.Name} {{ get; init; }}\n"
-
     sw.Write
         $"\tpublic override T accept<T>(IVisitor<T> visitor)
 \t{{
@@ -80,7 +80,7 @@ let renderAST outputDir baseName types =
 
 namespace Finn.AST;
 
-public abstract class {baseName} {{
+public abstract record {baseName}() {{
 \tpublic abstract T accept<T>(IVisitor<T> visitor);
 }}\n"