Fix instantation of CheckUnused phase

Author: szymon-rd

compiler/src/dotty/tools/dotc/Compiler.scala

@@ -35,7 +35,7 @@ class Compiler {
   protected def frontendPhases: List[List[Phase]] =
     List(new Parser) ::             // Compiler frontend: scanner, parser
     List(new TyperPhase) ::         // Compiler frontend: namer, typer
-    List(CheckUnused.PostTyper) ::  // Check for unused elements
+    List(new CheckUnused.PostTyper) ::  // Check for unused elements
     List(new YCheckPositions) ::    // YCheck positions
     List(new sbt.ExtractDependencies) :: // Sends information on classes' dependencies to sbt via callbacks
     List(new semanticdb.ExtractSemanticDB) :: // Extract info into .semanticdb files
@@ -50,7 +50,7 @@ class Compiler {
     List(new Pickler) ::            // Generate TASTY info
     List(new Inlining) ::           // Inline and execute macros
     List(new PostInlining) ::       // Add mirror support for inlined code
-    List(CheckUnused.PostInlining) ::  // Check for unused elements
+    List(new CheckUnused.PostInlining) ::  // Check for unused elements
     List(new Staging) ::            // Check staging levels and heal staged types
     List(new Splicing) ::           // Replace level 1 splices with holes
     List(new PickleQuotes) ::       // Turn quoted trees into explicit run-time data structures

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

@@ -53,6 +53,7 @@ class CheckUnused private (phaseMode: CheckUnused.PhaseMode, suffix: String, _ke
   // ========== SETUP ============
 
   override def prepareForUnit(tree: tpd.Tree)(using Context): Context =
+    println(this)
     val data = UnusedData()
     tree.getAttachment(_key).foreach(oldData =>
       data.unusedAggregate = oldData.unusedAggregate
@@ -304,8 +305,9 @@ object CheckUnused:
    */
   private val _key = Property.StickyKey[UnusedData]
 
-  val PostTyper =    new CheckUnused(PhaseMode.Aggregate, "PostTyper", _key)
-  val PostInlining = new CheckUnused(PhaseMode.Report, "PostInlining", _key)
+  class PostTyper extends CheckUnused(PhaseMode.Aggregate, "PostTyper", _key)
+
+  class PostInlining extends CheckUnused(PhaseMode.Report, "PostInlining", _key)
 
   /**
    * A stateful class gathering the infos on :

tests/neg-custom-args/fatal-warnings/i15503a.scala

@@ -63,12 +63,12 @@ object FooTypeName:
 
 object InlineChecks:
   object InlineFoo:
-    import collection.mutable.Set // OK
+    import collection.mutable.Set // ok
     import collection.mutable.Map // error
     inline def getSet = Set(1)
 
   object InlinedBar:
-    import collection.mutable.Set // error
+    import collection.mutable.Set // ok
     import collection.mutable.Map // error
     val a = InlineFoo.getSet