Micro-optimization: Make completion printing a Config option

Making completion printing a config option keeps the size of
key method `SymDenotations#completeFrom` small.

Author: odersky

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

@@ -144,6 +144,9 @@ object Config {
    */
   final val simplifyApplications = true
 
+  /** If set, prints a trace of all symbol completions */
+  final val showCompletions = false
+
   /** Initial size of superId table */
   final val InitialSuperIdsSize = 4096
 

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

@@ -27,7 +27,6 @@ object Printers {
   val incremental: Printer = noPrinter
   val config: Printer = noPrinter
   val transforms: Printer = noPrinter
-  val completions: Printer = noPrinter
   val cyclicErrors: Printer = noPrinter
   val pickling: Printer = noPrinter
   val inlining: Printer = noPrinter

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

@@ -17,7 +17,7 @@ import util.SimpleMap
 import util.Stats
 import java.util.WeakHashMap
 import config.Config
-import config.Printers.{completions, incremental, noPrinter}
+import config.Printers.{incremental, noPrinter}
 
 trait SymDenotations { this: Context =>
   import SymDenotations._
@@ -214,28 +214,31 @@ object SymDenotations {
       case _ => Some(myInfo)
     }
 
-    private def completeFrom(completer: LazyType)(implicit ctx: Context): Unit = {
-      if (completions ne noPrinter) {
-        completions.println(i"${"  " * indent}completing ${if (isType) "type" else "val"} $name")
+    private def completeFrom(completer: LazyType)(implicit ctx: Context): Unit =
+      if (Config.showCompletions) {
+        println(i"${"  " * indent}completing ${if (isType) "type" else "val"} $name")
         indent += 1
-      }
-      if (myFlags is Touched) throw CyclicReference(this)
-      myFlags |= Touched
-
-      // completions.println(s"completing ${this.debugString}")
-      try completer.complete(this)(ctx.withPhase(validFor.firstPhaseId))
-      catch {
-        case ex: CyclicReference =>
-          completions.println(s"error while completing ${this.debugString}")
-          throw ex
-      }
-      finally
-        if (completions ne noPrinter) {
+
+        if (myFlags is Touched) throw CyclicReference(this)
+        myFlags |= Touched
+
+        // completions.println(s"completing ${this.debugString}")
+        try completer.complete(this)(ctx.withPhase(validFor.firstPhaseId))
+        catch {
+          case ex: CyclicReference =>
+            println(s"error while completing ${this.debugString}")
+            throw ex
+        }
+        finally {
           indent -= 1
-          completions.println(i"${"  " * indent}completed $name in $owner")
+          println(i"${"  " * indent}completed $name in $owner")
         }
-      // completions.println(s"completed ${this.debugString}")
-    }
+      }
+      else {
+        if (myFlags is Touched) throw CyclicReference(this)
+        myFlags |= Touched
+        completer.complete(this)(ctx.withPhase(validFor.firstPhaseId))
+      }
 
     protected[dotc] def info_=(tp: Type) = {
       /* // DEBUG
@@ -797,7 +800,10 @@ object SymDenotations {
      */
     /** The class implementing this module, NoSymbol if not applicable. */
     final def moduleClass(implicit ctx: Context): Symbol = {
-      def notFound = { completions.println(s"missing module class for $name: $myInfo"); NoSymbol }
+      def notFound = {
+      	if (Config.showCompletions) println(s"missing module class for $name: $myInfo")
+      	NoSymbol
+      }
       if (this is ModuleVal)
         myInfo match {
           case info: TypeRef           => info.symbol

compiler/src/dotty/tools/dotc/typer/Namer.scala

@@ -16,7 +16,7 @@ import annotation.tailrec
 import ErrorReporting._
 import tpd.ListOfTreeDecorator
 import config.Config
-import config.Printers.{typr, completions, noPrinter}
+import config.Printers.{typr, noPrinter}
 import Annotations._
 import Inferencing._
 import transform.ValueClasses._
@@ -746,14 +746,13 @@ class Namer { typer: Typer =>
     }
 
     final override def complete(denot: SymDenotation)(implicit ctx: Context) = {
-      if (completions != noPrinter && ctx.typerState != this.ctx.typerState) {
-        completions.println(completions.getClass.toString)
+      if (Config.showCompletions && ctx.typerState != this.ctx.typerState) {
         def levels(c: Context): Int =
           if (c.typerState eq this.ctx.typerState) 0
           else if (c.typerState == null) -1
           else if (c.outer.typerState == c.typerState) levels(c.outer)
           else levels(c.outer) + 1
-        completions.println(s"!!!completing ${denot.symbol.showLocated} in buried typerState, gap = ${levels(ctx)}")
+        println(s"!!!completing ${denot.symbol.showLocated} in buried typerState, gap = ${levels(ctx)}")
       }
       assert(ctx.runId == creationContext.runId, "completing $denot in wrong run ${ctx.runId}, was created in ${creationContext.runId}")
       completeInCreationContext(denot)