add Scala 3 version of ShouldNotTypecheck

Author: SethTisue

build.sbt

@@ -44,5 +44,12 @@ lazy val testmacros = project.in(file("testmacros"))
   .settings(commonSettings)
   .settings(
     libraryDependencies += scalaOrganization.value % "scala-compiler" % scalaVersion.value,
-    publish / skip := true
+    publish / skip := true,
+    Compile / unmanagedSourceDirectories += {
+      val major = CrossVersion.partialVersion(scalaVersion.value) match {
+        case Some((0 | 3, _)) => "3"
+        case _ => "2"
+      }
+      baseDirectory.value / "src" / "main" / s"scala-$major"
+    },
   )

testmacros/src/main/scala/testutil/ShouldNotTypecheck.scala renamed to testmacros/src/main/scala-2/testutil/ShouldNotTypecheck.scala

@@ -0,0 +1,23 @@
+/*
+ * Scala (https://www.scala-lang.org)
+ *
+ * Copyright EPFL and Lightbend, Inc.
+ *
+ * Licensed under Apache License 2.0
+ * (http://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package testutil
+
+import scala.compiletime.testing._
+
+/**
+ * Ensures that a code snippet does not typecheck.
+ */
+object ShouldNotTypecheck {
+  inline def apply(code: String): Unit = assert(!typeChecks(code))
+  inline def apply(code: String, expected: String): Unit = apply(code)
+}