Fix checkTargets

main/src/main/scala/sbt/ProjectExtra.scala

@@ -357,31 +357,6 @@ trait ProjectExtra extends Scoped.Syntax:
     def setCond[T](key: AttributeKey[T], vopt: Option[T], attributes: AttributeMap): AttributeMap =
       attributes.setCond(key, vopt)
 
-    private[sbt] def checkTargets(data: Settings[Scope]): Option[String] =
-      val dups = overlappingTargets(allTargets(data))
-      if (dups.isEmpty) None
-      else {
-        val dupStrs = dups map { case (dir, scopes) =>
-          s"${dir.getAbsolutePath}:\n\t${scopes.mkString("\n\t")}"
-        }
-        Some(s"Overlapping output directories:${dupStrs.mkString}")
-      }
-
-    private[this] def overlappingTargets(
-        targets: Seq[(ProjectRef, File)]
-    ): Map[File, Seq[ProjectRef]] =
-      targets.groupBy(_._2).view.filter(_._2.size > 1).mapValues(_.map(_._1)).toMap
-
-    private[this] def allTargets(data: Settings[Scope]): Seq[(ProjectRef, File)] = {
-      import ScopeFilter._
-      val allProjects = ScopeFilter(Make.inAnyProject)
-      val targetAndRef = Def.setting { (Keys.thisProjectRef.value, Keys.target.value) }
-      new SettingKeyAll(Def.optional(targetAndRef)(identity))
-        .all(allProjects)
-        .evaluate(data)
-        .flatMap(x => x)
-    }
-
     private[sbt] def equalKeys(a: ScopedKey[_], b: ScopedKey[_], mask: ScopeMask): Boolean =
       a.key == b.key && Scope.equal(a.scope, b.scope, mask)
 

main/src/main/scala/sbt/internal/Load.scala

@@ -283,8 +283,7 @@ private[sbt] object Load {
       )
     }
 
-    // todo: fix this
-    // Project.checkTargets(data) foreach sys.error
+    checkTargets(data).foreach(sys.error)
     val index = timed("Load.apply: structureIndex", log) {
       structureIndex(data, settings, loaded.extra(data), projects)
     }
@@ -304,6 +303,29 @@ private[sbt] object Load {
     (rootEval, bs)
   }
 
+  private def checkTargets(data: Settings[Scope]): Option[String] =
+    val dups = overlappingTargets(allTargets(data))
+    if (dups.isEmpty) None
+    else {
+      val dupStr = dups.map { case (dir, scopes) =>
+        s"${dir.getAbsolutePath}:\n\t${scopes.mkString("\n\t")}"
+      }.mkString
+      Some(s"Overlapping output directories:$dupStr")
+    }
+
+  private def overlappingTargets(targets: Seq[(ProjectRef, File)]): Map[File, Seq[ProjectRef]] =
+    targets.groupBy(_._2).view.filter(_._2.size > 1).mapValues(_.map(_._1)).toMap
+
+  private def allTargets(data: Settings[Scope]): Seq[(ProjectRef, File)] = {
+    import ScopeFilter._
+    val allProjects = ScopeFilter(Make.inAnyProject)
+    val targetAndRef = Def.setting { (Keys.thisProjectRef.value, Keys.target.value) }
+    new SettingKeyAll(Def.optional(targetAndRef)(identity))
+      .all(allProjects)
+      .evaluate(data)
+      .flatMap(x => x)
+  }
+
   // map dependencies on the special tasks:
   // 1. the scope of 'streams' is the same as the defining key and has the task axis set to the defining key
   // 2. the defining key is stored on constructed tasks: used for error reporting among other things