Better reporting of nested implicit failures

Error messages of nested implicit failures are now
reported with the top-level message if -explaintypes is set.

2 files changed, 10 insertions, 7 deletions

diff --git a/compiler/src/dotty/tools/dotc/reporting/Reporter.scala b/compiler/src/dotty/tools/dotc/reporting/Reporter.scala
index 8477cfe28..26c1e5ebc 100644
--- a/compiler/src/dotty/tools/dotc/reporting/Reporter.scala
+++ b/compiler/src/dotty/tools/dotc/reporting/Reporter.scala
@@ -286,11 +286,16 @@ abstract class Reporter extends interfaces.ReporterResult {
   }
 
   /** Should this diagnostic not be reported at all? */
-  def isHidden(m: MessageContainer)(implicit ctx: Context): Boolean = ctx.mode.is(Mode.Printing)
+  def isHidden(m: MessageContainer)(implicit ctx: Context): Boolean =
+    ctx.mode.is(Mode.Printing)
 
   /** Does this reporter contain not yet reported errors or warnings? */
   def hasPending: Boolean = false
 
+  /** If this reporter buffers messages, remove and return all buffered messages. */
+  def removeBufferedMessages(implicit ctx: Context): List[MessageContainer] = Nil
+
   /** Issue all error messages in this reporter to next outer one, or make sure they are written. */
-  def flush()(implicit ctx: Context): Unit = {}
+  def flush()(implicit ctx: Context): Unit =
+    removeBufferedMessages.foreach(ctx.reporter.report)
 }
diff --git a/compiler/src/dotty/tools/dotc/reporting/StoreReporter.scala b/compiler/src/dotty/tools/dotc/reporting/StoreReporter.scala
index 586273c2e..34b109882 100644
--- a/compiler/src/dotty/tools/dotc/reporting/StoreReporter.scala
+++ b/compiler/src/dotty/tools/dotc/reporting/StoreReporter.scala
@@ -36,11 +36,9 @@ class StoreReporter(outer: Reporter) extends Reporter {
     }
   }
 
-  override def flush()(implicit ctx: Context) =
-    if (infos != null) {
-      infos.foreach(ctx.reporter.report(_))
-      infos = null
-    }
+  override def removeBufferedMessages(implicit ctx: Context): List[MessageContainer] =
+    if (infos != null) try infos.toList finally infos = null
+    else Nil
 
   override def errorsReported = hasErrors || outer.errorsReported
 }