diff --git a/hail/build.mill b/hail/build.mill
index a0c8cb1750f8..f047defbf22e 100644
--- a/hail/build.mill
+++ b/hail/build.mill
@@ -107,7 +107,7 @@ trait HailScalaModule extends ScalafmtModule with ScalafixModule { outer =>
   override def bspCompileClasspath: T[Agg[UnresolvedPath]] =
     super.bspCompileClasspath() ++ resources().map(p => UnresolvedPath.ResolvedPath(p.path))
 
-  trait HailTests extends ScalafmtModule with ScalafixModule with TestNg {
+  trait HailTests extends ScalaTests with TestNg with ScalafmtModule with ScalafixModule {
     override def forkArgs: T[Seq[String]] = Seq("-Xss4m", "-Xmx4096M")
 
     override def ivyDeps: T[Agg[Dep]] =
@@ -179,6 +179,10 @@ object `package` extends RootModule with SbtModule with HailScalaModule { outer
     buildInfo(),
   )
 
+  override def generatedSources: T[Seq[PathRef]] = Task {
+    Seq(`ir-gen`.generate())
+  }
+
   override def unmanagedClasspath: T[Agg[PathRef]] =
     Agg(shadedazure.assembly())
 
@@ -250,6 +254,19 @@ object `package` extends RootModule with SbtModule with HailScalaModule { outer
     PathRef(T.dest)
   }
 
+  object `ir-gen` extends HailScalaModule {
+    def ivyDeps = Agg(
+      ivy"com.lihaoyi::mainargs:0.6.2",
+      ivy"com.lihaoyi::os-lib:0.10.7",
+      ivy"com.lihaoyi::sourcecode:0.4.2",
+    )
+
+    def generate: T[PathRef] = Task {
+      runForkedTask(finalMainClass, Task.Anon { Args("--path", T.dest) })()
+      PathRef(T.dest)
+    }
+  }
+
   object memory extends JavaModule { // with CrossValue {
     override def zincIncrementalCompilation: T[Boolean] = false
 
diff --git a/hail/modules/ir-gen/src/Main.scala b/hail/modules/ir-gen/src/Main.scala
new file mode 100644
index 000000000000..a0ec0f4e581c
--- /dev/null
+++ b/hail/modules/ir-gen/src/Main.scala
@@ -0,0 +1,65 @@
+import mainargs.{ParserForMethods, main}
+
+sealed abstract class Trait(val name: String)
+
+object Trivial extends Trait("TrivialIR")
+
+sealed abstract class AttOrChild {
+  val name: String
+  def generateDeclaration: String
+}
+
+final case class Att(name: String, typ: String) extends AttOrChild {
+  override def generateDeclaration: String = s"$name: $typ"
+}
+
+final case class Child(name: String) extends AttOrChild {
+  override def generateDeclaration: String = s"$name: IR"
+}
+
+case class IR(
+  name: String,
+  attsAndChildren: Seq[AttOrChild],
+  traits: Seq[Trait] = Seq.empty,
+  extraMethods: Seq[String] = Seq.empty,
+) {
+  def withTraits(newTraits: Trait*): IR = copy(traits = traits ++ newTraits)
+  def withMethod(methodDef: String): IR = copy(extraMethods = extraMethods :+ methodDef)
+
+  def generateDef: String =
+    (s"final case class $name(${attsAndChildren.map(_.generateDeclaration).mkString(",")}) extends IR"
+      + traits.map(" with " + _.name).mkString
+      + (if (extraMethods.nonEmpty)
+           extraMethods.map("  " + _).mkString(" {\n", "\n", "\n}")
+         else ""))
+}
+
+object Main {
+  def node(name: String, attsAndChildren: AttOrChild*): IR = IR(name, attsAndChildren)
+
+  def allNodes: Seq[IR] = {
+    val r = Seq.newBuilder[IR]
+
+    r += node("I32", Att("x", "Int")).withTraits(Trivial)
+    r += node("I64", Att("x", "Long")).withTraits(Trivial)
+    r += node("F32", Att("x", "Float")).withTraits(Trivial)
+    r += node("F64", Att("x", "Double")).withTraits(Trivial)
+    r += node("Str", Att("x", "String")).withTraits(Trivial)
+      .withMethod(
+        "override def toString(): String = s\"\"\"Str(\"${StringEscapeUtils.escapeString(x)}\")\"\"\""
+      )
+    r += node("True").withTraits(Trivial)
+    r += node("False").withTraits(Trivial)
+    r += node("Void").withTraits(Trivial)
+
+    r.result()
+  }
+
+  @main
+  def main(path: String) = {
+    val gen = "package is.hail.expr.ir\n\n" + allNodes.map(_.generateDef).mkString("\n")
+    os.write(os.Path(path) / "IR_gen.scala", gen)
+  }
+
+  def main(args: Array[String]): Unit = ParserForMethods(this).runOrExit(args)
+}
diff --git a/hail/modules/src/main/scala/is/hail/expr/ir/IR.scala b/hail/modules/src/main/scala/is/hail/expr/ir/IR.scala
index 5f432ab2dd5c..fbec49f7dade 100644
--- a/hail/modules/src/main/scala/is/hail/expr/ir/IR.scala
+++ b/hail/modules/src/main/scala/is/hail/expr/ir/IR.scala
@@ -27,7 +27,7 @@ import java.io.OutputStream
 import org.json4s.{DefaultFormats, Extraction, Formats, JValue, ShortTypeHints}
 import org.json4s.JsonAST.{JNothing, JString}
 
-sealed trait IR extends BaseIR {
+trait IR extends BaseIR {
   private var _typ: Type = null
 
   def typ: Type = {
@@ -72,12 +72,12 @@ sealed trait IR extends BaseIR {
   def unwrap: IR = _unwrap(this)
 }
 
-sealed trait TypedIR[T <: Type] extends IR {
+trait TypedIR[T <: Type] extends IR {
   override def typ: T = tcoerce[T](super.typ)
 }
 
 // Mark Refs and constants as IRs that are safe to duplicate
-sealed trait TrivialIR extends IR
+trait TrivialIR extends IR
 
 object Literal {
   def coerce(t: Type, x: Any): IR = {
@@ -146,18 +146,18 @@ class WrappedByteArrays(val ba: Array[Array[Byte]]) {
   }
 }
 
-final case class I32(x: Int) extends IR with TrivialIR
-final case class I64(x: Long) extends IR with TrivialIR
-final case class F32(x: Float) extends IR with TrivialIR
-final case class F64(x: Double) extends IR with TrivialIR
+//final case class I32(x: Int) extends IR with TrivialIR
+//final case class I64(x: Long) extends IR with TrivialIR
+//final case class F32(x: Float) extends IR with TrivialIR
+//final case class F64(x: Double) extends IR with TrivialIR
 
-final case class Str(x: String) extends IR with TrivialIR {
-  override def toString(): String = s"""Str("${StringEscapeUtils.escapeString(x)}")"""
-}
+//final case class Str(x: String) extends IR with TrivialIR {
+//  override def toString(): String = s"""Str("${StringEscapeUtils.escapeString(x)}")"""
+//}
 
-final case class True() extends IR with TrivialIR
-final case class False() extends IR with TrivialIR
-final case class Void() extends IR with TrivialIR
+//final case class True() extends IR with TrivialIR
+//final case class False() extends IR with TrivialIR
+//final case class Void() extends IR with TrivialIR
 
 object UUID4 {
   def apply(): UUID4 = UUID4(genUID())