Assemble phases for -Vphases

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

@@ -12,7 +12,7 @@ import typer.Typer
 import typer.ImportInfo.withRootImports
 import Decorators.*
 import io.AbstractFile
-import Phases.{unfusedPhases, Phase}
+import Phases.{assemblePhases, unfusedPhases, Phase}
 
 import sbt.interfaces.ProgressCallback
 
@@ -270,19 +270,12 @@ class Run(comp: Compiler, ictx: Context) extends ImplicitRunInfo with Constraint
       report.echo(this.enrichErrorMessage(s"exception occurred while compiling ${files1.map(_.path)}"))
       throw ex
 
-  /** TODO: There's a fundamental design problem here: We assemble phases using `fusePhases`
-   *  when we first build the compiler. But we modify them with -Yskip, -Ystop
-   *  on each run. That modification needs to either transform the tree structure,
-   *  or we need to assemble phases on each run, and take -Yskip, -Ystop into
-   *  account. I think the latter would be preferable.
-   */
   def compileSources(sources: List[SourceFile]): Unit =
     if (sources forall (_.exists)) {
       units = sources.map(CompilationUnit(_))
       compileUnits()
     }
 
-
   def compileUnits(us: List[CompilationUnit]): Unit = {
     units = us
     compileUnits()
@@ -308,23 +301,9 @@ class Run(comp: Compiler, ictx: Context) extends ImplicitRunInfo with Constraint
       then ActiveProfile(ctx.settings.VprofileDetails.value.max(0).min(1000))
       else NoProfile
 
-    // If testing pickler, make sure to stop after pickling phase:
-    val stopAfter =
-      if (ctx.settings.YtestPickler.value) List("pickler")
-      else ctx.settings.YstopAfter.value
-
-    val runCtx = ctx.fresh
+    val runCtx = assemblePhases()
     runCtx.setProfiler(Profiler())
 
-    val pluginPlan = ctx.base.addPluginPhases(ctx.base.phasePlan)
-    val phases = ctx.base.fusePhases(pluginPlan,
-      ctx.settings.Yskip.value, ctx.settings.YstopBefore.value, stopAfter, ctx.settings.Ycheck.value)
-    ctx.base.usePhases(phases, runCtx)
-    val phasesSettings = List("-Vphases", "-Vprint")
-    for phasesSetting <- ctx.settings.allSettings if phasesSettings.contains(phasesSetting.name) do
-      for case vs: List[String] <- phasesSetting.userValue; p <- vs do
-        if !phases.exists(List(p).containsPhase) then report.warning(s"'$p' specifies no phase")
-
     if ctx.settings.YnoDoubleBindings.value then
       ctx.base.checkNoDoubleBindings = true
 
@@ -334,7 +313,7 @@ class Run(comp: Compiler, ictx: Context) extends ImplicitRunInfo with Constraint
       var phasesWereAdjusted = false
 
       var forceReachPhaseMaybe =
-        if (ctx.isBestEffort && phases.exists(_.phaseName == "typer")) Some("typer")
+        if (ctx.isBestEffort && allPhases.exists(_.phaseName == "typer")) Some("typer")
         else None
 
       for phase <- allPhases do

compiler/src/dotty/tools/dotc/config/CliCommand.scala

@@ -5,7 +5,9 @@ import scala.language.unsafeNulls
 
 import Settings.*
 import core.Contexts.*
+import core.Phases.assemblePhases
 import printing.Highlighting
+import transform.MegaPhase
 
 import scala.util.chaining.given
 import scala.PartialFunction.cond
@@ -117,9 +119,17 @@ trait CliCommand:
 
   /** Used for the formatted output of -Xshow-phases */
   protected def phasesMessage(using Context): String =
-    val phases = new Compiler().phases
+    val compiler = Compiler()
+    ctx.initialize()
+    ctx.base.setPhasePlan(compiler.phases)
+    val runCtx = assemblePhases()
+    val phases = runCtx.base.allPhases
+    val texts = phases.iterator.map {
+      case mp: MegaPhase => mp.miniPhases.iterator.map(p => (p.phaseName, p.description)).toList
+      case p => (p.phaseName, p.description) :: Nil
+    }.toList
     val formatter = Columnator("phase name", "description", maxField = 25)
-    formatter(phases.map(mega => mega.map(p => (p.phaseName, p.description))))
+    formatter(texts)
 
   /** Provide usage feedback on argument summary, assuming that all settings
    *  are already applied in context.

compiler/src/dotty/tools/dotc/core/Phases.scala

@@ -128,12 +128,12 @@ object Phases {
      */
     final def usePhases(phasess: List[Phase], runCtx: FreshContext, fuse: Boolean = true): Unit = {
 
-      val flatPhases = collection.mutable.ListBuffer[Phase]()
+      val flatPhases = ListBuffer.empty[Phase]
 
-      phasess.foreach(p => p match {
+      phasess.foreach {
         case p: MegaPhase => flatPhases ++= p.miniPhases
-        case _ => flatPhases += p
-      })
+        case p => flatPhases += p
+      }
 
       phases = (NoPhase :: flatPhases.toList ::: new TerminalPhase :: Nil).toArray
       setSpecificPhases()
@@ -561,4 +561,24 @@ object Phases {
   private def replace(oldPhaseClass: Class[? <: Phase], newPhases: Phase => List[Phase], current: List[List[Phase]]): List[List[Phase]] =
     current.map(_.flatMap(phase =>
       if (oldPhaseClass.isInstance(phase)) newPhases(phase) else phase :: Nil))
+
+  def assemblePhases()(using Context): FreshContext =
+    val runCtx = ctx.fresh
+
+    // If testing pickler, make sure to stop after pickling phase:
+    val stopAfter =
+      if (ctx.settings.YtestPickler.value) List("pickler")
+      else ctx.settings.YstopAfter.value
+
+    val pluginPlan = ctx.base.addPluginPhases(ctx.base.phasePlan)
+    val phases = ctx.base.fusePhases(pluginPlan,
+      ctx.settings.Yskip.value, ctx.settings.YstopBefore.value, stopAfter, ctx.settings.Ycheck.value)
+    ctx.base.usePhases(phases, runCtx)
+
+    val phasesSettings = List("-Vphases", "-Vprint")
+    for phasesSetting <- ctx.settings.allSettings if phasesSettings.contains(phasesSetting.name) do
+      for case vs: List[String] <- phasesSetting.userValue; p <- vs do
+        if !phases.exists(List(p).containsPhase) then report.warning(s"'$p' specifies no phase")
+    runCtx
+  end assemblePhases
 }