Set up AST class generation

Expr.g.cs

@@ -0,0 +1,52 @@
+////////////////////////////////////////////////////////////
+// THIS FILE IS GENERATED.                                //
+// DO NOT EDIT.                                           //
+////////////////////////////////////////////////////////////
+
+using System;
+namespace Finn.AST;
+
+public abstract class Expr {
+	public abstract T accept<T>(IVisitor<T> visitor);
+}
+public interface IVisitor<T> {
+	T visitBinaryExpr(Binary expr);
+	T visitGroupingExpr(Grouping expr);
+	T visitLiteralExpr(Literal expr);
+	T visitUnaryExpr(Unary expr);
+}
+public class Binary : 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 required Expr Expression { get; init; }
+	public override T accept<T>(IVisitor<T> visitor)
+	{
+		return visitor.visitGroupingExpr(this);
+	}
+}
+public class Literal : 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 required Token Op { get; init; }
+	public required Expr Right { get; init; }
+	public override T accept<T>(IVisitor<T> visitor)
+	{
+		return visitor.visitUnaryExpr(this);
+	}
+}

ast_classes.fsx

@@ -0,0 +1,65 @@
+type Field = { Type: string; Name: string }
+type Type = { Name: string; Fields: list<Field> }
+
+let types =
+    [ { Name = "Binary"
+        Fields =
+          [ { Type = "Expr"; Name = "Left" }
+            { Type = "Token"; Name = "Op" }
+            { Type = "Expr"; Name = "Right" } ] }
+      { Name = "Grouping"
+        Fields = [ { Type = "Expr"; Name = "Expression" } ] }
+      { Name = "Literal"
+        Fields =
+          [ { Type = "System.Object"
+              Name = "Value" } ] }
+      { Name = "Unary"
+        Fields = [ { Type = "Token"; Name = "Op" }; { Type = "Expr"; Name = "Right" } ] } ]
+
+let visitorMethod baseName t = $"visit{t.Name}{baseName}"
+
+let renderIVisitor (sw: System.IO.StreamWriter) (baseName: string) types =
+    sw.Write($"public interface IVisitor<T> {{\n")
+
+    for t in types do
+        sw.Write($"\tT {visitorMethod baseName t}({t.Name} {baseName.ToLower()});\n")
+
+    sw.Write("}\n")
+
+let renderType (sw: System.IO.StreamWriter) baseName t =
+    sw.Write
+        $"public class {t.Name} : {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{{
+\t\treturn visitor.{visitorMethod baseName t}(this);
+\t}}\n"
+
+    sw.Write("}\n")
+
+let renderAST outputDir baseName types =
+    let path = System.IO.Path.Combine(outputDir, baseName + ".g.cs")
+    use sw = new System.IO.StreamWriter(path)
+
+    sw.Write
+        $"////////////////////////////////////////////////////////////
+// THIS FILE IS GENERATED.                                //
+// DO NOT EDIT.                                           //
+////////////////////////////////////////////////////////////
+
+using System;
+namespace Finn.AST;
+
+public abstract class {baseName} {{
+\tpublic abstract T accept<T>(IVisitor<T> visitor);
+}}\n"
+
+    renderIVisitor sw baseName types
+    List.iter (renderType sw baseName) types
+
+renderAST "." "Expr" types

finn.csproj

@@ -5,4 +5,7 @@
     <RootNamespace>Finn</RootNamespace>
     <Nullable>enable</Nullable>
   </PropertyGroup>
+  <Target Name="GenerateASTClasses" BeforeTargets="BeforeBuild">
+    <Exec Command="dotnet fsi .\ast_classes.fsx" />
+  </Target>
 </Project>