From 83e6ad4bc2d8a74d1b661f8b700aa5aa94c3085e Mon Sep 17 00:00:00 2001
From: Aleksander Boruch-Gruszecki <aleksander.boruch-gruszecki@epfl.ch>
Date: Mon, 14 Jan 2019 19:02:54 +0100
Subject: [PATCH 1/2] Allow forcing traces

---
 .../dotty/tools/dotc/reporting/trace.scala    | 37 +++++++++++++------
 1 file changed, 26 insertions(+), 11 deletions(-)

diff --git a/compiler/src/dotty/tools/dotc/reporting/trace.scala b/compiler/src/dotty/tools/dotc/reporting/trace.scala
index eda7ebe16f97..284b0bc1def5 100644
--- a/compiler/src/dotty/tools/dotc/reporting/trace.scala
+++ b/compiler/src/dotty/tools/dotc/reporting/trace.scala
@@ -7,7 +7,8 @@ import config.Config
 import config.Printers
 import core.Mode
 
-object trace {
+abstract class TraceSyntax {
+  val isForced: Boolean
 
   @forceInline
   def onDebug[TD](question: => String)(op: => TD)(implicit ctx: Context): TD =
@@ -15,7 +16,7 @@ object trace {
 
   @forceInline
   def conditionally[TC](cond: Boolean, question: => String, show: Boolean)(op: => TC)(implicit ctx: Context): TC =
-    if (Config.tracingEnabled) {
+    if (isForced || Config.tracingEnabled) {
       def op1 = op
       if (cond) apply[TC](question, Printers.default, show)(op1)
       else op1
@@ -23,18 +24,18 @@ object trace {
 
   @forceInline
   def apply[T](question: => String, printer: Printers.Printer, showOp: Any => String)(op: => T)(implicit ctx: Context): T =
-    if (Config.tracingEnabled) {
+    if (isForced || Config.tracingEnabled) {
       def op1 = op
-      if (printer.eq(config.Printers.noPrinter)) op1
+      if (!isForced && printer.eq(config.Printers.noPrinter)) op1
       else doTrace[T](question, printer, showOp)(op1)
     }
     else op
 
   @forceInline
   def apply[T](question: => String, printer: Printers.Printer, show: Boolean)(op: => T)(implicit ctx: Context): T =
-    if (Config.tracingEnabled) {
+    if (isForced || Config.tracingEnabled) {
       def op1 = op
-      if (printer.eq(config.Printers.noPrinter)) op1
+      if (!isForced && printer.eq(config.Printers.noPrinter)) op1
       else doTrace[T](question, printer, if (show) showShowable(_) else alwaysToString)(op1)
     }
     else op
@@ -68,20 +69,27 @@ object trace {
     apply[T](s"==> $q?", (res: Any) => s"<== $q = ${showOp(res)}")(op)
   }
 
-  def apply[T](leading: => String, trailing: Any => String)(op: => T)(implicit ctx: Context): T =
+  def apply[T](leading: => String, trailing: Any => String)(op: => T)(implicit ctx: Context): T = {
+    val log: String => Unit = if (isForced) Console.println else {
+      var logctx = ctx
+      while (logctx.reporter.isInstanceOf[StoreReporter]) logctx = logctx.outer
+      logctx.log(_)
+    }
+    doApply(leading, trailing, log)(op)
+  }
+
+  def doApply[T](leading: => String, trailing: Any => String, log: String => Unit)(op: => T)(implicit ctx: Context): T =
     if (ctx.mode.is(Mode.Printing)) op
     else {
       var finalized = false
-      var logctx = ctx
-      while (logctx.reporter.isInstanceOf[StoreReporter]) logctx = logctx.outer
       def finalize(result: Any, note: String) =
         if (!finalized) {
           ctx.base.indent -= 1
-          logctx.log(s"${ctx.base.indentTab * ctx.base.indent}${trailing(result)}$note")
+          log(s"${ctx.base.indentTab * ctx.base.indent}${trailing(result)}$note")
           finalized = true
         }
     try {
-      logctx.log(s"${ctx.base.indentTab * ctx.base.indent}$leading")
+      log(s"${ctx.base.indentTab * ctx.base.indent}$leading")
       ctx.base.indent += 1
       val res = op
       finalize(res, "")
@@ -92,4 +100,11 @@ object trace {
         throw ex
     }
   }
+}
+
+object trace extends TraceSyntax {
+  final val isForced = false
+  object force extends TraceSyntax {
+    final val isForced = true
+  }
 }
\ No newline at end of file

From 9fb3521efa9e261199e0cec76886bf744e85693a Mon Sep 17 00:00:00 2001
From: Aleksander Boruch-Gruszecki <aleksander.boruch-gruszecki@epfl.ch>
Date: Tue, 12 Mar 2019 11:19:49 +0100
Subject: [PATCH 2/2] Document `trace`/`trace.force`

---
 .../dotty/tools/dotc/reporting/trace.scala    | 22 +++++++++++++------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/compiler/src/dotty/tools/dotc/reporting/trace.scala b/compiler/src/dotty/tools/dotc/reporting/trace.scala
index 284b0bc1def5..821f9ac6c85a 100644
--- a/compiler/src/dotty/tools/dotc/reporting/trace.scala
+++ b/compiler/src/dotty/tools/dotc/reporting/trace.scala
@@ -7,6 +7,21 @@ import config.Config
 import config.Printers
 import core.Mode
 
+/** Exposes the {{{ trace("question") { op } }}} syntax.
+  *
+  * Traced operations will print indented messages if enabled.
+  * Tracing depends on [[Config.tracingEnabled]] and [[dotty.tools.dotc.config.ScalaSettings.Ylog]].
+  * Tracing can be forced by replacing [[trace]] with [[trace.force]] (see below).
+  */
+object trace extends TraceSyntax {
+  final val isForced = false
+
+  /** Forces a particular trace to be printed out regardless of tracing being enabled. */
+  object force extends TraceSyntax {
+    final val isForced = true
+  }
+}
+
 abstract class TraceSyntax {
   val isForced: Boolean
 
@@ -101,10 +116,3 @@ abstract class TraceSyntax {
     }
   }
 }
-
-object trace extends TraceSyntax {
-  final val isForced = false
-  object force extends TraceSyntax {
-    final val isForced = true
-  }
-}
\ No newline at end of file