Don't run Ycheck for phases that do not transform trees

compiler/src/dotty/tools/dotc/sbt/ExtractAPI.scala

@@ -46,6 +46,9 @@ class ExtractAPI extends Phase {
     super.isRunnable && (ctx.sbtCallback != null || forceRun)
   }
 
+  // Check no needed. Does not transform trees
+  override def isCheckable: Boolean = false
+
   // SuperAccessors need to be part of the API (see the scripted test
   // `trait-super` for an example where this matters), this is only the case
   // after `PostTyper` (unlike `ExtractDependencies`, the simplication to trees

compiler/src/dotty/tools/dotc/sbt/ExtractDependencies.scala

@@ -54,6 +54,9 @@ class ExtractDependencies extends Phase {
     super.isRunnable && (ctx.sbtCallback != null || forceRun)
   }
 
+  // Check no needed. Does not transform trees
+  override def isCheckable: Boolean = false
+
   // This phase should be run directly after `Frontend`, if it is run after
   // `PostTyper`, some dependencies will be lost because trees get simplified.
   // See the scripted test `constants` for an example where this matters.

compiler/src/dotty/tools/dotc/transform/SetRootTree.scala

@@ -12,6 +12,9 @@ class SetRootTree extends Phase {
   override def isRunnable(implicit ctx: Context) =
     super.isRunnable && ctx.settings.YretainTrees.value
 
+  // Check no needed. Does not transform trees
+  override def isCheckable: Boolean = false
+
   override def run(implicit ctx: Context): Unit = {
     val tree = ctx.compilationUnit.tpdTree
     traverser.traverse(tree)