diff --git a/hail/build.mill b/hail/build.mill
index 9afdd012661c..d4804d43f0fa 100644
--- a/hail/build.mill
+++ b/hail/build.mill
@@ -73,7 +73,7 @@ object Deps {
   }
 }
 
-trait HailScalaModule extends SbtModule with ScalafmtModule with ScalafixModule { outer =>
+trait HailScalaModule extends ScalafmtModule with ScalafixModule { outer =>
   override def scalaVersion: T[String] = build.env.scalaVersion()
 
   override def javacOptions: T[Seq[String]] = Seq(
@@ -107,7 +107,7 @@ trait HailScalaModule extends SbtModule with ScalafmtModule with ScalafixModule
   override def bspCompileClasspath: T[Agg[UnresolvedPath]] =
     super.bspCompileClasspath() ++ resources().map(p => UnresolvedPath.ResolvedPath(p.path))
 
-  trait HailTests extends SbtTests with TestNg with ScalafmtModule with ScalafixModule {
+  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]] =
@@ -125,7 +125,7 @@ trait HailScalaModule extends SbtModule with ScalafmtModule with ScalafixModule
   }
 }
 
-object `package` extends RootModule with HailScalaModule { outer =>
+object `package` extends RootModule with HailScalaModule with SbtModule { outer =>
 
   override def millSourcePath: Path = super.millSourcePath / "modules"
 
@@ -179,6 +179,10 @@ object `package` extends RootModule 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 +254,18 @@ object `package` extends RootModule 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",
+    )
+
+    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
 
@@ -267,7 +283,7 @@ object `package` extends RootModule with HailScalaModule { outer =>
     }
   }
 
-  object test extends HailTests {
+  object test extends HailTests with SbtTests {
     override def resources: T[Seq[PathRef]] = outer.resources() ++ super.resources()
 
     override def assemblyRules: Seq[Rule] = outer.assemblyRules ++ Seq(
diff --git a/hail/modules/ir-gen/src/Main.scala b/hail/modules/ir-gen/src/Main.scala
new file mode 100644
index 000000000000..3597654d0d41
--- /dev/null
+++ b/hail/modules/ir-gen/src/Main.scala
@@ -0,0 +1,17 @@
+import mainargs.{ParserForMethods, main}
+//import os.pwd
+
+object Main {
+  @main
+  def main(path: String) = {
+    val gen =
+      """
+        |package is.hail.expr.ir
+        |
+        |final case class I32(x: Int) extends IR with TrivialIR
+        |""".stripMargin
+    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..e578de5bba4c 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 = {
@@ -146,7 +146,7 @@ class WrappedByteArrays(val ba: Array[Array[Byte]]) {
   }
 }
 
-final case class I32(x: Int) 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